WO2017002924A1

WO2017002924A1 - Nonwoven fabric and production method for same

Info

Publication number: WO2017002924A1
Application number: PCT/JP2016/069462
Authority: WO
Inventors: 育久白石; 泰弘城谷
Original assignee: 株式会社クラレ
Priority date: 2015-06-30
Filing date: 2016-06-30
Publication date: 2017-01-05
Also published as: JPWO2017002924A1; EP3318667B1; KR20180022911A; CN107709646A; US20180187353A1; EP3318667A4; CN107709646B; JP6617148B2; KR102403836B1; TWI675947B; EP3318667A1; TW201713809A

Abstract

Provided is a nonwoven fabric that includes fibers the principal component of which is a polymer with a glass transition temperature of 50°C or above, and that has a longitudinal strength of 1 N/5 cm or greater per 1 g/m², the nonwoven fabric satisfying both of the following conditions (1) and (2) and making it possible to provide a nonwoven fabric that has ample strength to be handled independently and that contains fibers having as the principal component a polymer with a Tg of 50°C or above, without performing any post-processing step such as an embossing step, calendaring step and spun lace step. Also provided is a production method for such nonwoven fabric. Condition (1): the density is 0.01-0.4 g/cm³. Condition (2): the proportion of sections having density exceeding 0.4 g/cm³ in a cross section taken in the thickness direction is 3% or less.

Description

Nonwoven fabric and method for producing the same

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

In recent years, nonwoven fabrics made of ultrafine fibers produced by the melt blown method have been developed and used for various purposes. Nonwoven fabrics using polymers with a glass transition temperature (Tg) of less than 50 ° C, such as polypropylene and polyethylene, can handle fibers without fusing, embossing, calendering, spunlace processing, etc. It is possible to obtain an excellent nonwoven fabric.

However, in a non-woven fabric using a polymer having a Tg of 50 ° C. or higher, if the fibers are not fused or three-dimensionally entangled by post-processing, the strength as the non-woven fabric is weak and the handleability is poor, and fluff is likely to occur. There was a problem such as.

Therefore, for such a nonwoven fabric, a method for solving the problem has been usually taken by performing post-processing (for example, JP 2012-41644 A (Patent Document 1)).

However, in the non-woven fabric that has been subjected to post-processing as described above, at least a part of the non-woven fabric has a high density part, which may affect performance such as air permeability, so there are few high density parts. Nevertheless, development of a nonwoven fabric excellent in handleability has been desired.

JP 2012-41644 A

The present invention has been made to solve the above-mentioned problems, and its purpose is to provide sufficient strength to handle alone without post-processing such as embossing, calendering, and spunlace processing. It is providing the nonwoven fabric containing the fiber which has Tg of 50 degreeC or more as a main component, and its manufacturing method.

The nonwoven fabric of the present invention is a nonwoven fabric containing fibers mainly composed of a polymer having a glass transition temperature of 50 ° C. or higher and having a vertical strength per 1 g / m ² of 1 N / 5 cm or more. It is a nonwoven fabric satisfying all of 2).
(1) The density is 0.01 to 0.4 g / cm ³ .
(2) The ratio of the portion where the density exceeds 0.4 g / cm ³ in the cross section in the thickness direction is 3% or less.

The nonwoven fabric of the present invention preferably has a fiber fusion rate of 15% or more in the cross section in the thickness direction, and an average area of each part 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 is also a method for producing the above-described nonwoven fabric of the present invention, wherein (1) the nozzle tip is set to the collection distance d between the spinning nozzle tip and the collection surface of the spun fiber. As a center, a hemispherical space of 0.5 × collection distance d, and (2) on the straight line with respect to the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber There is also provided a method for producing a nonwoven fabric, in which the melt blown method is carried out while maintaining the temperature at at least one of the points 1 cm from the collecting surface at a temperature higher by 10 ° C. than the glass transition temperature.

According to the present invention, a non-woven fabric comprising a fiber mainly composed of a polymer having a Tg of 50 ° C. or more and having sufficient strength to handle alone without post-processing such as embossing, calendering, and spunlace processing. And a method for manufacturing the same.

It is a SEM photograph of the section of the thickness direction of the nonwoven fabric of the present invention. It is a schematic diagram for demonstrating the principle of the manufacturing method of the nonwoven fabric of this invention. It is a schematic diagram for demonstrating the principle of the manufacturing method of the nonwoven fabric of this invention. It is a figure which shows typically a preferable example of the manufacturing method of the nonwoven fabric of this invention. It is a figure which shows typically the other preferable example of the manufacturing method of the nonwoven fabric of this invention. It is a SEM photograph of the section of the thickness direction at the time of carrying out calendering as post-processing, after making a nonwoven fabric by the melt blown method using the polymer whose Tg is 50 ° C or more. It is a SEM photograph of the section of the thickness direction at the time of embossing as post-processing, after making a nonwoven fabric by the melt blown method using the polymer whose Tg is 50 ° C or more. It is a SEM photograph of the section of the thickness direction at the time of performing spunlace processing as post-processing, after making a nonwoven fabric by the melt blown method using the polymer whose Tg is 50 ° C or more.

[1] Nonwoven fabric The nonwoven fabric of the present invention has a vertical strength (strength in the vertical direction (flow direction in the production of nonwoven fabric)) per 1 g / m ² is 1 N / 5 cm or more. According to the present invention, a non-woven fabric having sufficient strength that can be handled as a non-woven fabric independently without performing post-processing such as calendering, embossing, and spun lace processing that results in a part having a high density. Can be obtained. The strength of the nonwoven fabric of the present invention is more preferably 1.2 N / 5 cm or more, and further preferably 1.5 N / 5 cm. When non-woven fabric is formed by the conventional meltblown method and post-processing such as calendering, embossing, and spunlace processing is not performed (Comparative Example 1 described later), the vertical strength per 1 g / m ² is remarkably inferior. Thus, the non-woven fabric of the present invention is a non-woven fabric that is remarkably excellent in handleability even when compared with such a case.

The nonwoven fabric of the present invention is a nonwoven fabric having a density of 0.01 to 0.4 g / cm ³ . When the density is 0.01 g / cm ³ or more, the preferred form and properties of the nonwoven fabric can be maintained, and when the density is 0.4 g / cm ³ or less, the nonwoven fabric easily obtains desired performance such as high air permeability. It can be. The density of the nonwoven fabric of the present invention is preferably 0.35 g / cm ³ or less, more preferably 0.3 g / cm ³ or less, preferably 0.1 g / cm ³ or more, and More preferably, it is 11 g / cm ³ or more.

Furthermore, in the nonwoven fabric of the present invention, the proportion of the portion where the density exceeds 0.4 g / cm ³ is 3% or less. If the proportion of the portion where the density exceeds 0.4 g / cm ³ exceeds 3%, spots may occur on the nonwoven fabric, resulting in problems such as affecting the air permeability and causing spots of strength. The ratio of the portion where the density exceeds 0.4 g / cm ³ is more preferably 2.5% or less, and further preferably 2% or less.

The ratio of the location where the density in the above-mentioned nonwoven fabric exceeds 0.4 g / cm ³ was taken using a SEM, a photograph in which the cross section in the thickness direction of the nonwoven fabric was magnified 100 times, and this photograph was visually observed 10 mm in the width direction. In this straight line, the length occupied by the location exceeding the density of 0.4 g / cm ³ is measured, and the ratio of the location exceeding the density 0.4 g / cm ³ of the following formula (%)
= Length (mm) / 10 (mm) × 100 at a location exceeding density 0.4 g / cm ³
Find the ratio. Whether or not the density exceeds 0.4 g / cm ³ by observing the photograph is determined by using the function for measuring the distance between two points attached to the SEM, and the density is 0.4 g / cm ³ . The length is determined by examining the length occupied by the excess part.

Here, FIG. 1 is a scanning electron microscope (SEM) photograph of a cross-section in the thickness direction of the nonwoven fabric of the present invention (Example 1 described later) (FIG. 1 (a) is enlarged 100 times, FIG. 1 (b). Is magnified 1000 times). As shown in FIG. 1, the non-woven fabric of the present invention is a non-woven fabric 1 containing fibers mainly composed of a polymer having a Tg of 50 ° C. or higher, and the fibers 2 are partially fused (self-bonded). It has the fused part 3. Here, the nonwoven fabric 1 of the present invention preferably has a fiber fusion rate of 15% or more, more preferably 20% or more, and further preferably 25% or more in the cross section in the thickness direction. If the fiber fusion rate is less than 15%, the proportion of the fibers that are fused to each other in the nonwoven fabric is too low and the strength is insufficient, and handling alone is not possible, such as being unable to handle alone. May occur. Further, if the fiber fusion rate is too high, it may become a paper-like sheet or affect air permeability. Therefore, the fiber fusion rate of the nonwoven fabric is preferably 60% or less, and 50% The following is more preferable.

The fiber fusion rate of the nonwoven fabric described above can be calculated, for example, by the following procedure. First, using SEM, the photograph which expanded the cross section in the thickness direction of a nonwoven fabric 1000 times was image | photographed, and the cut | disconnection which fibers are fusing with respect to the number of fiber cut surfaces (fiber cross section) from this photograph visually. Find the ratio of the number of faces. Of the total number of fiber cross sections that can be found in each region, the ratio of the number of cross sections in which two or more fibers are fused is expressed by the following formula: Fiber fusion rate (%) = (cross section of two or more fused fibers) Number) / (total number of fiber cross-sections) × 100. However, for each photograph, all the fibers with a visible cross section are counted, and when the number of fiber cross sections is 100 or less, a photograph to be observed is added so that the total fiber cross section exceeds 100. In addition, in the part where the fibers are in contact with each other, there are a part that is simply in contact without fusing and a part that is adhered by fusing, but by cutting the nonwoven fabric for SEM photography, In the cross section, the fibers that are simply in contact with each other are separated by the stress of each fiber. Therefore, in the SEM photograph, it can be determined that the fibers in contact are fused.

In the nonwoven fabric of the present invention, the average area of each part where the fibers are fused is preferably 70 μm ² or less, more preferably 50 μm ² or less. Here, as a conventional example, FIGS. 6 to 8 show SEM photographs of cross sections in the thickness direction when a non-woven fabric produced by the melt blown method is post-processed. 6 shows a case where calendering is performed as post-processing (Comparative Example 3 to be described later) (FIG. 6A is enlarged 100 times, FIG. 6B is enlarged 1000 times), and FIG. 7 is embossed as post-processing. When processing is performed (Comparative Example 2 to be described later) (FIG. 7A is 100 times enlarged, FIG. 7B is 1000 times enlarged), FIG. 8 is a case where spunlace processing is performed as post-processing (described later). Comparative Example 4) (FIG. 8 (a) is enlarged 100 times, and FIG. 8 (b) is enlarged 1000 times). As is remarkable in FIGS. 6B and 7B, in the non-woven fabric subjected to calendering and embossing as post-processing, there are many portions where the fibers are fused to a state where it is difficult to determine the fiber diameter. The average area of each part formed and fused to the fiber is over 70 μm ² . In the nonwoven fabric of the present invention, the average area of each part where the fibers are fused is 70 μm ² or less, and as shown in FIG. 6 (b) and FIG. Differentiated from processed non-woven fabric. On the other hand, as shown in FIG. 8, in the nonwoven fabric subjected to spunlace processing, there are too few portions where the fibers are fused, and the fiber fusion rate is less than 15%. Thus, in the cross section in the thickness direction, the fiber fusion rate is 15% or more, and the average area of each part where the fibers are fused is 70 μm ² or less. It can be clearly distinguished from non-woven fabric that has undergone post-processing such as processing and spunlace processing.

The nonwoven fabric of the present invention preferably has an average fiber diameter in the range of 1 to 10 μm. As described above, the nonwoven fabric of the present invention preferably includes a fused portion where fibers are fused, but even in that case, when calendering is performed (see FIG. 6B), embossing is performed. Unlike the case where the processing is performed (see FIG. 7B), the fusion is such that the fiber diameter can be discriminated (FIG. 1B), and the average fiber diameter can be calculated. In the nonwoven fabric of the present invention, when the average fiber diameter is less than 1 μm, it is necessary to reduce the discharge amount, the productivity is lowered, the discharge pressure becomes unstable, the yarn breakage, the polymer lump May occur frequently, making it difficult to form the web. Moreover, in the nonwoven fabric of this invention, when an average fiber diameter exceeds 10 micrometers, there exists a possibility that it may be inferior to denseness. Among them, 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, for the reason of achieving both production stability and denseness, and preferably 1.5 to 9. A range of 0 μm is particularly preferable.

The nonwoven fabric of this invention contains the fiber which has a polymer whose Tg is 50 degreeC or more as a main component.
In the present invention, the fiber mainly composed of a polymer having a Tg of 50 ° C. or more is a fiber containing 50% by mass or more of a polymer having a Tg of 50 ° C. or more, and the content thereof is preferably 70% by mass or more. More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more, Most preferably, it is 100 mass%.

Further, the nonwoven fabric of the present invention may contain two or more different types of polymers having a Tg of 50 ° C. or more as long as the total of polymers having a Tg of 50 ° C. or more is 50% by mass or more.

Examples of the polymer having a Tg of 50 ° C. or higher used in the present invention include polyamide, polyphenylene sulfide, polyethylene terephthalate, and polycarbonate. From the viewpoint of both flame retardancy and heat resistance, amorphous polyetherimide (PEI). Is particularly preferred.

Amorphous PEI used in the present invention is a polymer containing an aliphatic, alicyclic or aromatic ether unit and a cyclic imide as a repeating unit, and has an amorphous property and melt moldability. If it does not specifically limit. In addition, within the range that does not inhibit the effect of the present invention, the main chain of amorphous PEI has a structural unit other than cyclic imide and ether bond, such as aliphatic, alicyclic or aromatic ester unit, oxycarbonyl unit, etc. It may be contained.

As the amorphous PEI used in the present invention, a polymer represented by the following general formula is preferably used. In which R1 is a divalent aromatic residue having 6 to 30 carbon atoms, and R2 is a divalent aromatic residue having 6 to 30 carbon atoms, and 2 to 20 carbons. A divalent selected from the group consisting of an alkylene group having an atom, a cycloalkylene group having 2 to 20 carbon atoms, and a polydiorganosiloxane group chain-terminated with an alkylene group having 2 to 8 carbon atoms. Organic group.

The amorphous PEI used in the present invention preferably has a melt viscosity at 330 ° C. of 100 to 3000 Pa · s. When the melt viscosity of amorphous PEI at 330 ° C. is less than 100 Pa · s, there may be frequent occurrence of resin particles called shots that occur because spinning or fibers cannot be formed during spinning. When the melt viscosity at 330 ° C. of amorphous PEI exceeds 3000 Pa · s, it may be difficult to make ultrafine fibers, oligomers may be generated during polymerization, and troubles may occur during polymerization or granulation. The melt viscosity at 330 ° C. is preferably 200 to 2700 Pa · s, and more preferably 300 to 2500 Pa · 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 resulting nonwoven fabric may have poor heat resistance. Further, the higher the glass transition temperature of amorphous PEI, the more preferable because a nonwoven fabric excellent in heat resistance can be obtained. However, if it is too high, the fusion temperature will be high when fused, and the polymer will be polymerized at the time of fusion. May cause decomposition. The glass transition temperature of amorphous PEI is more preferably 200 to 230 ° C, and further preferably 205 to 220 ° C.

The molecular weight of the amorphous PEI used in the present invention is not particularly limited, but the weight average molecular weight (Mw) is 1000 considering the mechanical properties, dimensional stability, and process passability of the resulting fiber or nonwoven fabric. It is preferably ˜80000. The use of a polymer having a high molecular weight is preferable because it is excellent in terms of fiber strength, heat resistance and the like, but from the viewpoint of resin production cost, fiberization cost, etc., the weight average molecular weight is preferably 2000 to 50000, and 3000 to 40000. It is more preferable that

In the present invention, from the viewpoint of amorphousness, melt moldability, and cost, amorphous PEI includes 2,2-bis [4- (2,3-dicarboxyl) mainly having a structural unit represented by the following formula. A condensate of phenoxy) phenyl] propane dianhydride with m-phenylenediamine or p-phenylenediamine is preferably used. This PEI is commercially available from Servic Innovative Plastics under the trademark “Ultem”.

In the fiber mainly composed of a polymer having a Tg of 50 ° C. or more, which is contained in the nonwoven fabric of the present invention, an antioxidant, an antistatic agent, a radical inhibitor, a matting agent, and the like within a range not impairing the effects of the present invention. An ultraviolet absorber, a flame retardant, an inorganic substance, etc. may be included. Specific examples of such inorganic substances include carbon nanotubes, fullerene, talc, wollastonite, zeolite, sericite, mica, kaolin, clay, pyrophyllite, silica, bentonite, alumina silicate and other silicates, silicon oxide, magnesium oxide, Metal oxides such as alumina, zirconium oxide, titanium oxide and iron oxide, carbonates such as calcium carbonate, magnesium carbonate and dolomite, sulfates such as calcium sulfate and barium sulfate, calcium hydroxide, magnesium hydroxide and aluminum hydroxide Hydroxides, glass beads, glass flakes, glass powders, ceramic beads, boron nitride, silicon carbide, carbon black, graphite and the like are used. Furthermore, for the purpose of improving the hydrolysis resistance of the fiber, an end group blocking agent such as a mono- or diepoxy compound, a mono- or polycarbodiimide compound, a mono- or dioxazoline compound, or a mono- or diazirine compound may be included.

In addition, the nonwoven fabric of the present invention includes fibers other than fibers mainly composed of a polymer having a Tg of 50 ° C. or higher, for example, fibers made of polyethylene, polypropylene, ethylene vinyl acetate, and the like within a range not impairing the effects of the present invention. You may go out. The content of the fiber mainly composed of a polymer having a Tg of 50 ° C. or higher is not particularly limited, but is preferably 50% by mass or more, more preferably 70% by mass or more, and 90% by mass or more. More preferably, it is particularly preferably 100% by mass.

The thickness of the nonwoven fabric of the present invention is not particularly limited, but is preferably in the range of 10 to 1000 μm, more preferably in the range of 15 to 500 μm, and in the range of 20 to 200 μm. It is particularly preferred. If the thickness of the nonwoven fabric is less than 10 μm, there is a risk that the strength will be low and it will break during processing, and if the thickness of the nonwoven fabric exceeds 1000 μm, it will be difficult to form a web. There is a fear.

The nonwoven fabric of the present invention preferably has an air permeability of 10 cc / cm ² / sec or more, more preferably 20 cc / cm ² / sec or more, and 130 cc / cm ² / sec or less. Preferably, it is 120 cc / cm ² / sec or less. By being in the said range, it can use suitably also for uses, such as a filter.

The basis weight of the nonwoven fabric of the present invention is not particularly limited, but is preferably in the range of 10 to 1000 g / m ² , and more preferably in the range of 15 to 500 g / m ² . When the basis weight of the nonwoven fabric is less than 10 g / m ² , there is a possibility that the strength becomes low and breaks during processing, and when the basis weight of the nonwoven fabric exceeds 1000 g / m ² , productivity is increased. From the viewpoint of

[2] Method for Producing Nonwoven Fabric The present invention also provides a method for suitably producing the above-described nonwoven fabric of the present invention. In addition, the nonwoven fabric of the present invention described above is a nonwoven fabric including fibers mainly composed of a polymer having a Tg of 50 ° C. or higher and having a vertical strength per 1 g / m ² of 1 N / 5 cm or more, and has a density of 0.00. 01 to 0.4 g / cm ³ , if the ratio of the portion where the density exceeds 0.4 g / cm ³ in the cross section in the thickness direction is 3% or less, the nonwoven fabric was produced by the method for producing a nonwoven fabric of the present invention. Although not necessarily manufactured by the method for manufacturing a nonwoven fabric of the present invention, it is preferably manufactured by the method for manufacturing a nonwoven fabric of the present invention.

The method for producing a nonwoven fabric of the present invention is carried out by performing the melt blown method while maintaining the temperature in at least one of the following (1) and (2) at a temperature higher by 10 ° C. or more than the Tg of the main polymer. It is characterized by.

(1) A hemispherical space of 0.5 × collection distance d around the nozzle tip, with respect to the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber,
(2) A point 1 cm from the collection surface on the straight line with respect to the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber.

When two or more different polymers having a Tg of 50 ° C. or higher are used, the polymer is held at a temperature that is 10 ° C. 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 method for producing a nonwoven fabric of the present invention. FIG. 2 shows a state where the meltblown method is performed using the meltblown device 11. After the polymer fiber 13 is discharged (spun) from the spinning nozzle 12 of the meltblown device 11, the meltblown device 11 captures it with a rotating roll 14. Collected to form a web (sheets made by overlapping fibers) 15. Hot air (primary air) 16 for spinning is discharged along with the polymer fiber 13 from the spinning nozzle 12 of the melt blown device 11 and flows along the curved surface of the roll 14. At that time, the inventors flow cold air as an accompanying flow 17 toward the spinning nozzle 12, so that the polymer fiber 13 discharged from the tip 12 a of the spinning nozzle 12 is on the surface of the roll 14 (spun). It was found that the web 15 having low strength and poor handleability was formed due to rapid cooling before reaching the fiber collection surface 14a. For this reason, conventionally, it has been necessary to perform post-processing such as calendering, embossing, and spunlace (hydraulic) processing to impart strength to the web to make a nonwoven fabric. The temperature of the primary air discharged from the tip of the spinning nozzle actually measured by the inventors (measured using a contact-type temperature sensor) was 420 ° C., but 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 nonwoven fabric manufacturing method of the present invention, as shown in FIG. 3, the radius x centered on the tip 12a of the spinning nozzle 12 is between the tip 12a of the spinning nozzle 12 and the collecting surface 14a of the spun fiber 13. With respect to the collection distance d, the hemispherical space A of 0.5 × collection distance d around the nozzle tip and / or the tip 12a of the spinning nozzle 12 and the collection surface 14a of the spun fiber 13 are collected. The temperature at a point B (not shown) of 1 cm from the collection surface on the straight line is maintained at a temperature 10 ° C. higher than the Tg of the polymer. Here, in the method for producing a nonwoven fabric of the present invention, the temperature in either the space A or the point B may be maintained at a temperature higher by 10 ° C. or more than the Tg of the polymer. May be maintained at a temperature 15 ° C. or higher than the Tg of the polymer. In addition, as in the example illustrated 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 above-described space A and point B at a temperature that is 10 ° C. or more higher than Tg, cooling of the primary air by the accompanying flow as described above is prevented, and Tg is 50 ° C. or more. The nonwoven fabric of the present invention having a polymer as a main component and having fibers fused together and having sufficient strength can be produced without post-processing such as calendering, embossing, and spunlace processing (that is, The web 15 collected by the roll 14 can be used as a non-woven fabric as it is).

Here, with respect to the collection distance d of the surface between the tip 12a of the spinning nozzle 12 and the collection surface 14a of the spun fiber 13, about the nozzle tip, 0.5 × collection distance d is a radius x. When the temperature of the hemispherical space A 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 centering on the tip 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, providing a thermocouple type thermometer as a thermometer at any position on the curved surface constituting the hemisphere assumed as the boundary of the space A, for example. .

In addition, when the point B 1 cm above the collection surface on the straight line is higher than the linear distance d between the tip 12a of the spinning nozzle 12 and the collection surface 14a of the spun fiber 13 by 10 ° C. or more, The temperature of the surrounding space is not particularly limited.

In the method for producing a nonwoven fabric of the present invention, the temperature in at least one of the space A and the point B is maintained at 10 ° C. or more (more preferably in the range of 15 to 60 ° C.) than the Tg of the polymer. When the temperature in at least one of the space A and the point B is equal to or lower than the Tg of the polymer or less than 10 ° C. even if the temperature is higher than the Tg, the effect of preventing the spun fibers from being cooled by the accompanying flow Is insufficient, there is a risk of producing a nonwoven fabric with low strength and inferior handleability.

FIG. 4 is a diagram schematically showing a preferred example of the method for producing a nonwoven fabric of the present invention. In the example shown in FIG. 4, the tip 12a of the spinning nozzle 12 is blown toward the tip 12a of the spinning nozzle 12 so that hot air (this hot air is referred to as “secondary air”) 22 is blown toward the above-described primary air. A hot air jet device 21 is provided in the vicinity. Although the method of providing the hot air jetting device 21 is not particularly limited, the hot air jetting device 21 having a shape that continuously forms the circumference surrounding the tip 12a of the spinning nozzle 12 is used, and the blowing destination of the hot air jetting device 21 is that of the spinning nozzle 12. It may be provided so as to be directed toward the tip 12a, or a plurality of hot air ejection devices 21 are provided around the tip 12a so that the blowing destination is the tip 12a of the spinning nozzle 12. Also good. For example, as described above, the melt blown method can be performed while maintaining the temperature in at least one of (1) and (2) at a temperature higher by 10 ° C. or more than the Tg of the polymer as described above. It becomes. In addition, as a hot-air ejection apparatus 21, a conventionally well-known appropriate hot-air ejection apparatus can be especially used without a restriction | limiting.

The temperature of the secondary air 22 ejected by the hot air ejecting device 21 so as to blow into the tip 12a of the spinning nozzle 12 is the temperature in at least one of (1) and (2) (particularly, the space (1)). Is not particularly limited as long as it can be maintained at a temperature 30 ° C. or higher than the Tg of the polymer, but is preferably 35 to 70 ° C. higher than the polymer Tg, and 35 to 60 ° C. higher than the polymer Tg. It is more preferable. When the temperature of the secondary air 22 is less than 30 ° C. higher than the Tg of the polymer, the temperature is maintained in at least one of the above (1) and (2) (particularly the space (1)). It tends to be difficult, and there is little fiber fusion and the nonwoven fabric strength tends to be weak. Further, when the temperature of the secondary air 22 is higher than the polymer Tg by more than 70 ° C., the fiber fusion tends to increase and the paper-like nonwoven fabric tends to be formed. Also, with respect to the flow rate of the secondary air 22, the temperature in at least one of (1) and (2) (especially the space in (1) above) can be maintained at a temperature higher by 10 ° C. or more than the Tg of the polymer. is not particularly limited if, in order not to disturb the flow of the primary air, preferably in the range of 3 ~ 12Nm 3 / ^m, and more preferably in a range of 4 ~ 10Nm 3 / ^m .

FIG. 5 is a diagram schematically showing another preferred example of the method for producing a nonwoven fabric of the present invention. In the example shown in FIG. 5, at least a part of the space between the tip 12 a of the spinning nozzle 12 and the collection surface 14 a of the spun fiber is covered with the cover 31. As a result, the primary air discharged from the tip 12a of the spinning nozzle 12 stays in the space covered by the cover 31 as the circulating air 32, and is not covered by such a cover 31, The primary air discharged from the tip 12a of the spinning nozzle 12 is not rapidly cooled by the accompanying flow. Even in this manner, as described above, the melt blown method can be performed while maintaining the temperature in at least one of (1) and (2) at a temperature higher by 10 ° C. or more than the Tg of the polymer. Become. If the temperature in at least one of the above (1) and (2) can be maintained at a temperature higher by 10 ° C. or more than the Tg of the polymer, the cover 31 can be connected to the tip 12a of the spinning nozzle 12 and the spinning. It is not necessary to cover the entire area between the collected fibers 14a. As in the example shown in FIG. 5, the cover 31 is preferably provided so as to cover the entire area between the tip 12a of the spinning nozzle 12 and the collection surface 14a of the spun fiber. The material for forming such a cover 31 is not particularly limited as long as it has heat resistance that does not deteriorate due to the temperature of the primary air, and examples thereof include metals such as SUS, aluminum, and copper. However, SUS is preferable from the viewpoint of durability, workability, and heat resistance.

In the method for producing a nonwoven fabric of the present invention, the temperature in at least one of the above (1) and (2) is maintained at a temperature 10 ° C. or more higher than the Tg of the polymer, the melt blown method is performed, calendering, embossing, Except for not performing post-processing such as spunlace processing, the same processes and conditions as in the conventional meltblown method can be suitably employed. Examples of the 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 amount of 5 to 25 Nm ³ per 1 m of the nozzle length. Of course not limited.

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

[Nonwoven fabric density (g / cm ³ )]
The volume of the nonwoven fabric was measured using [basis weight of nonwoven fabric] and [nonwoven fabric thickness], and the density of the nonwoven fabric was calculated from these results.

[Proportion (%) where the density exceeds 0.4 g / cm ³ ]
Using a scanning electron microscope, a photograph in which the cross section in the thickness direction of the nonwoven fabric was magnified 100 times was photographed, and a straight line of 10 mm in the width direction was visually observed, and the density of 0.4 g was included in this straight line. Measure the length occupied by locations exceeding / cm ³ , and the following formula: Ratio of locations exceeding density 0.4 g / cm ³ (%)
= Length (mm) / 10 (mm) × 100 at a location exceeding density 0.4 g / cm ³
Find the ratio. Incidentally, by observing the photographs, density whether exceeds 0.4 g / cm ³ using a function between two points a distance measurement that comes with SEM, beyond the density 0.4 g / cm ³ It is determined by examining the length of the location.

[Vertical strength (strength in the vertical direction (flow direction)) (N / 5cm)]
The nonwoven fabric was cut into a width of 5 cm, and an autograph manufactured by Shimadzu Corporation was used, and the nonwoven fabric was stretched at a pulling rate of 10 cm / min according to JIS L 1906.

[Melt viscosity]
Using a Toyo Seiki Capillograph Model 1B, measurement was performed under conditions of a temperature of 330 ° C. and a shear rate of r = 1200 sec ⁻¹ .

[Glass transition temperature (℃)]
The glass transition temperature was measured by measuring the temperature dependence of loss tangent (tan δ) at a frequency of 10 Hz and a heating rate of 10 ° C./min using a solid dynamic viscoelastic device “RheoSpectra DVE-V4” manufactured by Rheology. It was determined from the peak temperature. Here, the peak temperature of tan δ is a temperature at which the first derivative of the amount of change with respect to the temperature of the value of tan δ becomes zero.

[Fiber fusion rate (%)]
Using a scanning electron microscope, a photograph in which the cross section in the thickness direction of the nonwoven fabric was enlarged 1000 times was taken, and fibers were fused to the number of fiber cut surfaces (fiber cross sections) visually from this photograph. The ratio of the number of cut surfaces was determined. Of the total number of fiber cross sections that can be found in each region, the ratio of the number of cross sections in which two or more fibers are fused is expressed by the following formula: Fiber fusion rate (%) = (cross section of two or more fused fibers) Number) / (total number of fiber cross-sections) × 100. However, for each photograph, all the fibers with a visible cross section were counted, and when the number of fiber cross sections was 100 or less, a photograph to be observed was added so that the total fiber cross section exceeded 100.

[Average of area of each part where fibers are fused]
Using a scanning electron microscope, a photograph was taken with the cross section in the thickness direction of the nonwoven fabric magnified 1000 times, and from this photograph, the area of the portion where the fibers were fused was calculated, and the total was the portion where the fibers were fused The average value was obtained by dividing by the number of.

[Average fiber diameter (μm)]
The nonwoven fabric was magnified and photographed with a scanning electron microscope, the diameter of 100 arbitrary fibers was measured, the average value was calculated, and the average fiber diameter was obtained.

[Basis weight of non-woven fabric (g / m ² )]
In accordance with JIS L 1913, a sample piece of 20 cm in length and 20 cm in width was collected, the mass was measured with an electronic balance, and divided by a test piece area of 400 cm ² , the mass per unit area was taken as the basis weight.

[Thickness of non-woven fabric (μm)]
In accordance with JIS L 1913, using the same sample piece as the basis weight measurement, each sample piece was measured at five locations with a digital thickness gauge (Toyo Seiki Seisakusho: B1 type) with a diameter of 16 mm and a load of 20 gf / cm ^2. And the average value of 15 points | pieces was made into the thickness of a sheet | seat.

[Air permeability of non-woven fabric (cc / cm ² / sec)]
The air permeability was measured in accordance with the fragile method of JIS L1913 “General Nonwoven Test Method”.

<Example 1>
Amorphous polyetherimide having a melt viscosity of 500 Pa · s at 330 ° C. is used and extruded by an extruder. Nozzle hole diameter D (diameter) 0.3 mm, L (nozzle length) / D = 10, nozzle hole Supplied to a melt blown device having nozzles with a pitch of 0.75 mm, sprayed at a single-hole discharge rate of 0.09 g / min, spinning temperature of 390 ° C., hot air (primary air) temperature of 420 ° C., nozzle width of 10 Nm ³ / min per 1 m of nozzle width, A nonwoven fabric having a basis weight of 25 g / m ² was produced. At this time, a hot air blowing device such as the example shown in FIG. 4 is provided so that hot air (secondary air) is blown into the tip of the spinning nozzle of the melt blown device, and hot air (secondary air) at a temperature of 260 ° C. is 2 Nm ³ . Sprayed at the flow rate toward the tip of the spinning nozzle. The linear distance d between the tip of the spinning nozzle and the receiving surface of the roller that receives the spun fiber is 10 cm, and is provided so as to be positioned on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle. The temperature measured by a thermometer (AD-5601A (manufactured by A & I Co.)) was 235 ° C. (that is, the space A was 20 ° C. higher than 215 ° C., which is the glass transition temperature of amorphous PEI). ℃ was kept high). In addition, a thermometer (AD-5601A (A • 5A) provided so as to be located on the straight line 1 cm from the collection surface with respect to a linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber. And i)) was measured at 242 ° C. (ie, point B was held 27 ° C. higher than 215 ° C., the glass transition temperature of amorphous PEI). In this way, a nonwoven fabric was obtained without post-processing. As an SEM photograph of a cross section in the thickness direction of the obtained nonwoven fabric, FIG. 1 (a) shows an image magnified 100 times, and FIG.

<Example 2>
A hemisphere with an amorphous polyetherimide having a melt viscosity of 900 Pa · s at 330 ° C., a spinning temperature of 420 ° C., an average fiber diameter of 3.7 μm, and a radius x = 5 cm centered on the tip of the spinning nozzle The temperature measured by a thermometer located on the outer periphery of the shape is 253 ° C. (that is, the space A is kept 38 ° C. higher than 215 ° C., which is the glass transition temperature of amorphous PEI), and the tip of the spinning nozzle The temperature measured by a thermometer provided so as to be 1 cm from the collection surface on the straight line d with respect to the collection surface of the spun fiber is 261 ° C. (that is, the point B is The non-woven fabric was obtained in the same manner as in Example 1 except that the glass transition temperature of amorphous PEI was maintained at 46 ° C. higher than 215 ° C.

<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>
An amorphous polycarbonate having a melt viscosity at 300 ° C. of 100 Pa · s is used and extruded by an extruder. Nozzle hole diameter D (diameter) 0.3 mm, L (nozzle length) / D = 10, nozzle hole pitch 0 Supplied to melt blown device with nozzle of .75mm, single hole discharge rate 0.09g / min, spinning temperature 340 ° C, hot air (primary air) temperature 370 ° C, sprayed at 10Nm ³ / min per 1m nozzle width, basis weight Produced a 25 g / m ² nonwoven fabric. At this time, a hot air blowing device such as the example shown in FIG. 4 is provided so that hot air (secondary air) is blown into the tip of the spinning nozzle of the melt blown device, and hot air (secondary air) at a temperature of 210 ° C. is 2 Nm ³ . Sprayed at the flow rate toward the tip of the spinning nozzle. The linear distance d between the tip of the spinning nozzle and the receiving surface of the roller that receives the spun fiber is 10 cm, and is provided so as to be positioned on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle. The temperature measured by a thermometer (AD-5601A (manufactured by A & I Co., Ltd.)) was 185 ° C. (that is, space A was 50 ° C. higher than 135 ° C., which is the glass transition temperature of amorphous polycarbonate). ℃ was kept high). In addition, a thermometer (AD-5601A (A • 5A) provided so as to be located on the straight line 1 cm from the collection surface with respect to a linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber. The temperature measured by Andi Co.) was 192 ° C. (that is, the point B was maintained 57 ° C. higher than the glass transition temperature of 135 ° C. of the amorphous polycarbonate).

<Comparative Example 1>
A non-woven fabric was obtained in the same manner as in Example 2 except that no hot-air ejection device was provided (the temperature measured by a thermometer located on the outer circumference of a hemisphere having a radius x = 5 cm centered on the tip of the spinning nozzle) The temperature measured by a thermometer provided at 41 ° C. so that the linear distance d between the tip of the spinning nozzle and the collection surface of the spun fiber is 1 cm from the collection surface on the straight line is 110 ° C.).

<Comparative Example 2>
Using the embossing apparatus, the nonwoven fabric obtained in Comparative Example 1 was post-embossed with a grid pattern embossing roll under the conditions of a roll temperature of 180 ° C., a linear pressure of 50 kg / cm, and a speed of 1 m / min. It was. As an SEM photograph of a cross section in the thickness direction of the obtained nonwoven fabric, FIG. 7 (a) shows an image magnified 100 times, and FIG. 7 (b) shows an image magnified 1000 times.

<Comparative Example 3>
Using a calendering device (iron roll), the nonwoven fabric obtained in Comparative Example 1 was calendered as post-processing under the conditions of a roll temperature of 180 ° C., a linear pressure of 216 kg / cm, and a speed of 3.2 m / min. . As an SEM photograph of the cross section in the thickness direction of the obtained nonwoven fabric, FIG. 6 (a) shows an image magnified 100 times, and FIG. 6 (b) shows an image magnified 1000 times.

<Comparative Example 4>
Using the hydroentanglement apparatus, the nonwoven fabric obtained in Comparative Example 1 was subjected to hydroentanglement as post-processing at a speed of 5.0 m / min using a 0.1 mmφ hole diameter nozzle, 0.5 MPa, Hydroentanglement treatment was performed in three stages of 0.0 MPa and 2.5 MPa. As an SEM photograph of the cross section in the thickness direction of the obtained nonwoven fabric, FIG. 8 (a) shows an image magnified 100 times, and FIG. 8 (b) shows an image magnified 1000 times.

<Comparative Example 5>
A nonwoven fabric was obtained under the same conditions as in Example 2 except that the temperature of hot air (secondary air) was 240 ° C. The temperature measured by a thermometer located on the outer circumference of a hemisphere with a radius x = 5 cm centered on the tip of the spinning nozzle is 220 ° C., the linear distance between the tip of the spinning nozzle and the collection surface of the spun fiber The temperature measured by a thermometer provided so as to be located 1 cm from the collection surface on the straight line with respect to d was 217 ° C.

The results are shown in Tables 1 and 2.

Since the nonwoven fabric of the present invention is excellent in handleability despite its low density, it can be used not only in combination with various substrates and other nonwoven fabrics, but also suitably used in filters that require air permeability. The

DESCRIPTION OF SYMBOLS 1 Nonwoven fabric, 2 fibers, 3 melt | fusion part, 11 meltblown apparatus, 12 spinning nozzle, 12a air outlet, 13 spun amorphous polymer fiber, 14 roll, 14a roll receiving surface, 15 nonwoven fabric, 16 primary air, 17 Adjoining flow, 21 hot air jetting device, 22 secondary air, 31 cover, 32 circulating air.

Claims

A nonwoven fabric containing fibers mainly composed of a polymer having a glass transition temperature of 50 ° C. or more and having a vertical strength per 1 g / m 2 of 1 N / 5 cm or more, and satisfies all of the following (1) to (2) Nonwoven fabric to do.
(1) The density is 0.01 to 0.4 g / cm 3 .
(2) The ratio of the portion where the density exceeds 0.4 g / cm 3 in the cross section in the thickness direction is 3% or less.
2. The nonwoven fabric according to claim 1, wherein the fiber fusion rate is 15% or more in the cross section in the thickness direction, and the average area of each portion where the fibers are fused is 70 μm 2 or less.
The nonwoven fabric according to claim 1, wherein the average fiber diameter is 1 to 10 µm.
The nonwoven fabric according to claim 1, comprising amorphous polyetherimide fiber.
A method for producing the nonwoven fabric according to any one of claims 1 to 4,
(1) With respect to the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber, a hemispherical space of 0.5 × collection distance d around the nozzle tip, and
(2) The temperature at at least one of the points 1 cm from the collection surface on the straight line with respect to the collection distance d between the tip of the spinning nozzle and the collection surface of the spun fiber is the glass transition temperature. A method for producing a nonwoven fabric, wherein the melt blown method is carried out while maintaining the temperature higher by 10 ° C. or higher.