JP2024115948A - Nonwoven fabrics, filters, prepregs, printed wiring boards and electronic components - Google Patents

Abstract

[Problem] To provide a nonwoven fabric that has excellent heat resistance and excellent structural strength even if the fibers are thin. [Solution] The nonwoven fabric of the present disclosure includes fibers that include fibers (A) that contain a 4-methyl-1-pentene polymer (A). The glass transition temperature difference ΔTg of the fibers (A) measured by a differential scanning calorimeter (DSC) is 4.0°C or more. The average fiber diameter of the fibers is 10 μm or less. [Selected Figures] None

Description

This disclosure relates to nonwoven fabrics, filters, prepregs, printed wiring boards and electronic components.

Fibers containing 4-methyl-1-pentene polymers are used in a wide range of applications, taking advantage of their heat resistance and dielectric properties (for example, Patent Document 1 and Patent Document 2).

International Publication No. 2005/098118 JP 2007-211378 A

Meltblown nonwoven fabrics have excellent flexibility, uniformity, and density, and also have a small fiber diameter. The average fiber diameter of the fibers in meltblown nonwoven fabrics is usually 10 μm or less. Meltblown nonwoven fabrics alone, or nonwoven fabric laminates containing meltblown nonwoven fabrics and other nonwoven fabrics, are used in many fields. Specifically, meltblown nonwoven fabrics are used as separation membranes (e.g., porous sheets for gas permeable films, etc.), electrolytic capacitors, separators for polymer batteries, filters, light diffusing materials, liquid absorbers, and heat insulating materials.

However, meltblown nonwoven fabrics containing 4-methyl-1-pentene polymers tend to have inferior mechanical properties (e.g., structural strength, etc.). Therefore, meltblown nonwoven fabrics containing 4-methyl-1-pentene polymers may have problems in being used in applications that require excellent mechanical properties.

For example, bag filters are used to collect high-temperature dust discharged from industrial facilities (e.g., incinerators, coal-fired boilers, metal melting furnaces, etc.). The size of the high-temperature dust passing through the filter of the bag filter is relatively large. Therefore, the filter of the bag filter may be required to have excellent mechanical properties in addition to filtration performance and heat resistance.
Like bag filters, prepregs used in printed wiring boards are sometimes required to have heat resistance and certain levels of mechanical properties.
Therefore, there is a demand for nonwoven fabrics that are excellent in heat resistance and structural strength (i.e., tensile strength in the MD (machine direction)) even when the fibers are thin (i.e., even when the average fiber diameter of the fibers is 10 μm or less).

This disclosure has been made in consideration of the above problems, and aims to provide nonwoven fabrics, filters, prepregs, printed wiring boards, and electronic components that have excellent heat resistance and excellent structural strength even when the fibers are thin.

Means for solving the above problems include the following aspects:

<1> A fiber including a fiber (A) containing a 4-methyl-1-pentene polymer (A),
The glass transition temperature difference ΔTg of the fiber (A) measured by a differential scanning calorimeter (DSC) is 4.0° C. or more,
The nonwoven fabric, wherein the average fiber diameter of the fibers is 10 μm or less.
<2> A mixed fiber nonwoven fabric,
The fibers further include fibers (B) containing an amorphous thermoplastic resin (B),
The nonwoven fabric according to <1>, wherein the glass transition temperature difference ΔTg of the fibers (B) measured by a differential scanning calorimeter (DSC) is 0.8° C. or more.
<3> The nonwoven fabric according to <1> or <2>, having a specific surface area of 1.3 m ² /g or more.
<4> The nonwoven fabric according to any one of <1> to <3> above, having a structural strength of 10 N/50 mm or more.
<5> The 4-methyl-1-pentene polymer (A),
90 to 100 mol % of structural units derived from 4-methyl-1-pentene;
0 to 10 mol % of structural units derived from olefins having 2 to 20 carbon atoms other than 4-methyl-1-pentene;
The nonwoven fabric according to any one of <1> to <4>,
<6> The amorphous thermoplastic resin (B) contains a cyclic olefin polymer (B-1),
The cyclic olefin polymer (B-1) contains at least one selected from a cyclic olefin copolymer (B-1-1) and a ring-opening polymer of a cyclic olefin (B-1-2),
The nonwoven fabric according to <2> above, wherein the cyclic olefin copolymer (B-1-1) contains the following structural unit (a) and the following structural unit (b):
Structural unit (a): At least one structural unit derived from an olefin compound represented by the following general formula (I).
Structural unit (b): a structural unit derived from a cyclic olefin compound, which is at least one selected from the group consisting of a structural unit represented by the following general formula (II), a structural unit represented by the following general formula (III), and a structural unit represented by the following general formula (IV):

In the above general formula (I), R ³⁰⁰ is a hydrogen atom, or a linear or branched hydrocarbon group having 1 to 29 carbon atoms.

In the general formula (II), u is 0 or 1, v is 0 or a positive integer, and w is 0 or 1. R ⁶¹ to R ⁷⁸ as well as R ^a1 and R ^b1 may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, or an aromatic hydrocarbon group having 6 to 20 carbon atoms. At least two of R ⁷⁵ to R ⁷⁸ may be bonded to each other to form a monocycle or polycycle.

In the general formula (III), x and d are each independently 0 or an integer of 1 or more. y and z are each independently an integer of 0 to 2. R ⁸¹ to R ⁹⁹ may be the same or different and are a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group which is an alkyl group having 1 to 20 carbon atoms or a cycloalkyl group having 3 to 15 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or an alkoxy group. The carbon atom to which R ⁸⁹ and R ⁹⁰ are bonded may be bonded directly or via an alkylene group having 1 to 3 carbon atoms to the carbon atom to which R ⁹³ is bonded or the carbon atom to which R ⁹¹ is bonded. When y=z=0, R ⁹² and R ⁹⁵ or R ⁹⁵ and R ⁹⁹ may be bonded to each other to form a monocyclic or polycyclic aromatic ring.

In the general formula (IV), R ¹⁰⁰ and R ¹⁰¹ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. f is in the range of 1≦f≦18.
<7> The nonwoven fabric according to <6>, wherein the cyclic olefin polymer (B-1) contains the cyclic olefin copolymer (B-1-1).
<8> The nonwoven fabric according to <7>, wherein the cyclic olefin copolymer (B-1-1) contains the structural unit (a) and the following structural unit (c):
Structural unit (c): a structural unit represented by the above general formula (II), in which u is 0 and v is 1.
<9> The nonwoven fabric according to any one of <2> and <6> to <8>, wherein the glass transition temperature Tg of the fiber (B) measured by a differential scanning calorimeter (DSC) is 85° C. or higher.
<10> A filter comprising the nonwoven fabric according to any one of <1> to <9>.
<11> The filter according to <10>, wherein the filter is a bag filter.
<12> The nonwoven fabric according to any one of <1> to <9>,
A resin composition including at least one of a thermosetting resin and a thermoplastic resin;
A prepreg comprising:
<13> The thermosetting resin is a thermosetting resin having a curing temperature that is 20° C. or more lower than the lowest melting point of the nonwoven fabric,
The prepreg according to <12>, wherein the thermoplastic resin has a melting point that is 20° C. or more lower than the lowest melting point in the nonwoven fabric.
<14> A cured or solidified product of the prepreg according to <12>,
a conductor layer that is disposed on one or both sides of the cured product or the solidified product and that has been subjected to wiring processing;
A printed wiring board comprising:
<15> An electronic component having a circuit for transmitting an electrical signal of 1 GHz or more,
An electronic component having an insulating layer containing a cured or solidified product of the prepreg according to <12>.

This disclosure makes it possible to provide nonwoven fabrics, filters, prepregs, printed wiring boards, and electronic components that have excellent heat resistance and excellent structural strength even when the fibers are thin.

1(a) to 1(i) show an example of a spinneret having a multi-component spinning nozzle used in the method for producing a nonwoven fabric of the present disclosure.

In the present disclosure, the use of "to" indicating a range of numerical values means that the numerical values before and after it are included as the lower limit and upper limit.
In the present disclosure, in the ranges described stepwise, the upper or lower limit value described in one range may be replaced with the upper or lower limit value of another range described stepwise. In the ranges described in the present disclosure, the upper or lower limit value of the range may be replaced with the value shown in the examples.
In the present disclosure, the term "step" refers not only to an independent step, but also to a step that cannot be clearly distinguished from other steps, as long as the intended purpose of the step is achieved.
In this disclosure, when referring to the amount of each component in a composition, if multiple substances corresponding to each component are present in the composition, it means the total amount of multiple substances present in the composition, unless otherwise specified.
In this disclosure, "nonwoven fabric" refers to a flat assembly of fibers that has a certain level of structural integrity achieved by physical and/or chemical processes, excluding weaving, knitting, and papermaking.
In this disclosure, "web" refers to a sheet composed solely of fibers.
In this disclosure, "split fiber" refers to a fiber that has the property of being split from a single fiber into multiple fibers.

(1) Nonwoven Fabric The nonwoven fabric of the present disclosure (hereinafter also simply referred to as "nonwoven fabric") comprises fibers (hereinafter also simply referred to as "fibers") including fibers (A) containing a 4-methyl-1-pentene polymer (A). The glass transition temperature difference ΔTg (hereinafter also referred to as "ΔTg(A)") of the fibers (A) measured by a differential scanning calorimeter (DSC) is 4.0° C. or more. The average fiber diameter of the fibers is 10 μm or less.

In the present disclosure, the term "4-methyl-1-pentene polymer (A)" refers to a polymer mainly composed of structural units derived from 4-methyl-1-pentene. Specifically, the proportion of the structural units derived from 4-methyl-1-pentene is 90 mol % to 100 mol % based on the total amount of the 4-methyl-1-pentene polymer (A).
In the present disclosure, the "average fiber diameter of the fibers" refers to the average fiber diameter of the fibers constituting the nonwoven fabric of the present disclosure. When the fibers include fiber (A) and fiber (B) described below, the "average fiber diameter of the fibers" refers to the average fiber diameter of the entire fibers including fiber (A) and fiber (B). The method for measuring the average fiber diameter of the fibers is the same as that described in the Examples.

In the present disclosure, the term "glass transition temperature difference ΔTg of fiber (A)" refers to the temperature difference between the first glass transition temperature of fiber (A) and the second glass transition temperature of fiber (A). The term "first glass transition temperature of fiber (A)" refers to the glass transition temperature of fiber (A) measured by a differential scanning calorimeter (DSC) when fiber (A) taken from a nonwoven fabric is melted by first heating at a heating rate of 10°C/min, then solidified by cooling at a heating rate of 10°C/min, and then melted by second heating at a heating rate of 10°C/min. The term "second glass transition temperature of fiber (A)" refers to the glass transition temperature of fiber (A) measured by the second heating. The method for measuring the glass transition temperature is the same as that described in the Examples.

When the glass transition temperature difference ΔTg of the 4-methyl-1-pentene polymer (A) is 4.0° C. or more, the fiber (A) can be evaluated as being a fiber produced by a spunbond method. The reason is as follows.
Generally, the glass transition of polymers is explained as a relaxation caused by the micro-branch motion of amorphous chains. Methods for increasing the glass transition temperature include oriented crystallization by stretching and binding between molecular chains. It is also known that stretching in the solid state is more suitable for achieving higher molecular orientation than stretching in the molten state. Therefore, it is presumed that the molecular orientation of the fibers in the nonwoven fabric obtained by the spunbonding method through solid-state stretching is promoted, and as a result, the glass transition temperature of the fibers is higher than that in the non-oriented state.
In ΔTg(A), it can be evaluated that the first glass transition temperature of fiber (A) corresponds to the glass transition temperature of fiber (A) in a state where molecular orientation is promoted, and the second glass transition temperature of fiber (A) corresponds to the glass transition temperature of fiber (A) in a non-oriented state. In other words, the first glass transition temperature of fiber (A) is higher than the second glass transition temperature of fiber (A).
The glass transition temperature difference ΔTg of the fibers produced by the meltblown method is usually less than 4.0°C.

The nonwoven fabric of the present disclosure has the above-mentioned configuration, and therefore has excellent heat resistance and structural strength even though the fibers are thin. Furthermore, the nonwoven fabric of the present disclosure has excellent dielectric properties and heat resistance, as well as excellent filtration performance and structural strength.

The nonwoven fabric is a sheet-like material. The structure of the nonwoven fabric is appropriately selected depending on the application of the nonwoven fabric, and may be, for example, a single-layer structure or a multi-layer structure of two or more layers. When the application of the nonwoven fabric is a filter or prepreg, the structure of the nonwoven fabric is preferably a single-layer structure.

The nonwoven fabric preferably includes a spunbond nonwoven fabric, and more preferably is a spunbond nonwoven fabric. The nonwoven fabric may include other nonwoven fabrics, woven fabrics, knitted fabrics, paper, etc. The other nonwoven fabrics may be short fiber nonwoven fabrics or long fiber nonwoven fabrics. Examples of other nonwoven fabrics include meltblown nonwoven fabrics, wet nonwoven fabrics, hydroentangled nonwoven fabrics, dry nonwoven fabrics, dry pulp nonwoven fabrics, airlaid nonwoven fabrics, flash spun nonwoven fabrics, tow-spread nonwoven fabrics, needle punch nonwoven fabrics, long fiber cellulose fiber nonwoven fabrics, etc.

The nonwoven fabric of the present disclosure is preferably a mixed fiber nonwoven fabric, and the fibers further include a fiber (B) containing an amorphous thermoplastic resin (B). The glass transition temperature difference ΔTg (hereinafter also referred to as "ΔTg(B)") of the fiber (B) measured by a differential scanning calorimeter (DSC) is 0.8°C or more. Details of the fiber (B) will be described later.

In the present disclosure, the term "mixed fiber nonwoven fabric" refers to a nonwoven fabric in which fibers made of different resins are mixed at the spinning stage.
In the present disclosure, the term "amorphous thermoplastic resin" refers to a thermoplastic resin that does not have a clear melting point as measured by a differential scanning calorimeter (DSC).

In the present disclosure, the term "glass transition temperature difference ΔTg of fiber (B)" refers to the temperature difference between the first glass transition temperature of fiber (B) and the second glass transition temperature of fiber (B). The term "first glass transition temperature of fiber (B)" refers to the glass transition temperature of fiber (B) measured by a differential scanning calorimeter (DSC) when fiber (B) sampled from a nonwoven fabric is melted by first heating at a heating rate of 10° C./min, then solidified by cooling at a heating rate of 10° C./min, and then melted by second heating at a heating rate of 10° C./min. The term "second glass transition temperature of fiber (B)" refers to the glass transition temperature of fiber (B) measured by the second heating.
When the nonwoven fabric of the present disclosure is a mixed fiber nonwoven fabric, the measurement object of the glass transition temperature difference ΔTg of each of the fibers (A) and (B) may be each of the fibers (A) and (B) sorted out from the mixed fiber nonwoven fabric, or may be the mixed fiber nonwoven fabric itself. The glass transition temperatures Tg of each of the fibers (A) and (B) are different. Therefore, even if the measurement object is the mixed fiber nonwoven fabric itself, the glass transition temperatures Tg of each of the fibers (A) and (B) can be determined from the measurement results of the mixed fiber nonwoven fabric itself by DSC.

The nonwoven fabric of the present disclosure is a mixed fiber nonwoven fabric, and the fibers further contain fiber (B), so that the nonwoven fabric has better filter performance and mechanical properties. This effect is presumed to be due to, but not limited to, the following reasons.
The mixed fiber nonwoven fabric of the present disclosure is preferably obtained by producing a plurality of split fibers by the spunbond method and splitting one split fiber into a plurality of fibers. In general, it is considered that in order to improve the splittability of the split fiber, it is necessary that the compatibility between the resins constituting the split fiber is low. In particular, in the combination of a crystalline thermoplastic resin and an amorphous thermoplastic resin, the amorphous thermoplastic resin is easily excluded from the crystal structure when the crystalline thermoplastic resin crystallizes. Therefore, it is presumed that the interface between the different resins in the split fiber remains compatible at the macro level. Therefore, it is presumed that the combination of a crystalline thermoplastic resin such as a 4-methyl-1-pentene polymer (A) and an amorphous thermoplastic resin (B) has a very high splittability of the split fiber.
The high splitting property of split fibers promotes a reduction in the average fiber diameter and an improvement in the filtering performance and structural strength of the nonwoven fabric. Specifically, the ease of splitting of split fibers indicates that unsplit fibers are less likely to remain. Therefore, the average fiber diameter of split fibers becomes smaller. Particle collection occurs when particles adhere to the fiber surface that constitutes the filter. Therefore, an increase in the surface area of the fiber (i.e., thinning of the fiber) improves the filtering performance of the nonwoven fabric. Furthermore, the ease of splitting of split fibers indicates that there are more points of contact between split fibers. Therefore, split fibers can bear a larger frictional force. As a result, the structural strength of the nonwoven fabric is improved.
The performance of electronic materials is strongly dependent on the properties of resins, such as their dielectric constant and dielectric loss tangent. In particular, the 4-methyl-1-pentene polymer (A) and the cyclic olefin polymer (B-1) described below are known as thermoplastic resins with small dielectric constants and dielectric loss tangents. For this reason, it is presumed that the nonwoven fabric will exhibit excellent electronic material performance.

The thickness of the nonwoven fabric is not particularly limited and may be appropriately selected depending on the application of the nonwoven fabric, and may be 0.05 mm to 100 mm, or 0.02 mm to 50 mm.
The method for measuring the thickness of the nonwoven fabric is the same as that described in the Examples.

The basis weight of the nonwoven fabric is not particularly limited and may be appropriately selected depending on the application of the nonwoven fabric, and may be 1 g/m ² to 400 g/m ² or 5 g/m ² to 100 g/m ² .
The method for measuring the basis weight of the nonwoven fabric is the same as that described in the Examples.

The specific surface area of the nonwoven fabric is not particularly limited and is appropriately selected depending on the application of the nonwoven fabric. From the viewpoint of obtaining a nonwoven fabric excellent in filtration performance and structural strength, the specific surface area of the nonwoven fabric is preferably 0.5 m ² /g or more, more preferably 0.8 m ² /g or more, even more preferably 1.0 m ² /g or more, and particularly preferably 1.3 m ² /g or more. The specific surface area may be, for example, 3.0 m ² /g or less. From these viewpoints, the specific surface area of the nonwoven fabric may be 0.5 m ² /g to 3.0 ^{m 2} /g.
The specific surface area of the nonwoven fabric was measured in the same manner as described in the Examples.

The structural strength of the nonwoven fabric is not particularly limited and may be appropriately selected depending on the application of the nonwoven fabric, and is preferably 10 N/50 mm or more. This allows the nonwoven fabric to be applied to prepregs used in bag filters and printed wiring boards, for example.
The structural strength of the nonwoven fabric is more preferably 15 N/50 mm or more, further preferably 20 N/50 mm or more, and particularly preferably 25 N/50 mm or more, from the viewpoint of application to prepregs used in, for example, bag filters and printed wiring boards. The structural strength of the nonwoven fabric may be, for example, 100 N/50 mm or less. From these viewpoints, the structural strength of the nonwoven fabric may be 10 N/50 mm to 100 N/50 mm.
The method for measuring the structural strength of the nonwoven fabric is the same as that described in the Examples.
Examples of methods for adjusting the structural strength of the nonwoven fabric within the above range include the type of resin, the shape of the spinneret having a composite spinning nozzle, the fiber molding conditions, or the pressure of the high-pressure liquid flow and the number of treatments in the splitting step described below. Specifically, the spinning temperature is preferably 260°C to 350°C. The discharge rate per hole is preferably 0.1 g/min to 5 g/min. The speed (air volume) of the stretching air is preferably ¹⁰⁰⁰ Nm3/h/m to 50000 ^Nm3 /h/m.

The formation index of the nonwoven fabric is not particularly limited and may be appropriately selected depending on the application of the nonwoven fabric, etc. The formation index of the nonwoven fabric is not particularly limited and may be, for example, 5 to 300.
The method for measuring the formation index of the nonwoven fabric is the same as that described in the Examples.

The quality factor (Q value) of a nonwoven fabric indicates an index of the performance of the nonwoven fabric filter. The Q value of the nonwoven fabric is appropriately selected depending on the application of the nonwoven fabric, and is preferably 0.08 or more, more preferably 0.1 or more, and even more preferably 0.14 or more, from the viewpoint of application to a bag filter, for example. The Q value of the nonwoven fabric is not particularly limited, but is preferably 0.5 or less, and more preferably 0.4 or less. From these viewpoints, the Q value of the nonwoven fabric may be 0.08 to 0.5.

The Q value of a nonwoven fabric is a value calculated by the following formula (a) using the collection efficiency and pressure loss. As shown in the formula below, the lower the pressure loss and the higher the collection performance, the higher the Q value, and it can be seen that the filtration performance is good when the nonwoven fabric is used as a filter.
Formula (a): Q value (Pa ⁻¹ )=−[ln(1−[collection efficiency])/(pressure loss (Pa))]
In formula (a), the collection efficiency indicates the collection efficiency of the nonwoven fabric described above, and the pressure loss (Pa) indicates the pressure loss of the nonwoven fabric described above.

The nonwoven fabric of the present disclosure can be used in a wide range of applications for which nonwoven fabrics are typically used. Examples of applications for nonwoven fabrics include filters, sanitary materials, medical components, packaging materials, battery separators, heat retaining materials, insulation materials, protective clothing, clothing components, electronic materials, sound absorbing materials, civil engineering materials, etc.

The nonwoven fabric can be preferably used as a filter such as a gas filter (air filter) or a liquid filter. The nonwoven fabric of the present disclosure is preferably used for a high-performance filter having excellent filtering performance. It is useful for manufacturing a bag filter for collecting high-temperature dust (e.g., high-temperature dust generated by an incinerator, a coal-fired boiler, a metal melting furnace, etc.).
Since nonwoven fabrics have excellent heat resistance and mechanical properties, they are preferably used as prepregs.

The nonwoven fabric may be electrically charged depending on the application. An electrically charged nonwoven fabric is suitable for use in air filters. An electrically charged nonwoven fabric can be obtained by subjecting a nonwoven fabric to an electrostatic charging process.

(1.1) Fibers The average fiber diameter of the fibers is 10 μm or less. From the viewpoint of obtaining a nonwoven fabric having excellent filtration performance and structural strength, the average fiber diameter of the fibers is preferably 8 μm or less, more preferably 7 μm or less, and even more preferably 6 μm or less. The average fiber diameter of the fibers may be, for example, 1 μm or more, or 2 μm or more. From these viewpoints, the average fiber diameter of the fibers may be 1 μm to 10 μm.
The method for measuring the average fiber diameter of the fibers is the same as that described in the Examples.

The coefficient of variation (CV) value of the fiber is not particularly limited, but is preferably 70% or less, more preferably 65% or less, and further preferably 60% or less. The CV value may be 10% or more.
The method for measuring the CV value of the fiber is the same as that described in the examples.

The fibers may be long or short fibers. The cross-sectional shape of the fibers is not particularly limited, and examples include circular, elliptical, and irregular cross-sectional shapes.

The fibers may be composite fibers or monocomponent fibers. Composite fibers preferably have two or more thermoplastic resins as their constituent components. Examples of composite fibers include core-sheath type, side-by-side type, sea-island type, and parallel type.

(1.1.1) Fiber (A)
The fibers include fibers (A).

ΔTg(A) is 4.0° C. or more. From the viewpoint of obtaining a nonwoven fabric excellent in filtration performance and structural strength, ΔTg(A) is preferably 6.0° C. or more, more preferably 8.0° C. or more, and even more preferably 10° C. or more. ΔTg(A) may be, for example, 20° C. or less, or 18° C. or less. From these viewpoints, ΔTg(A) may be 4.0° C. to 20° C.
The method for measuring ΔTg(A) is the same as that described in the Examples.

The average fiber diameter and CV value of fiber (A) may be the same as those of the fibers described above.

Fiber (A) may be a long fiber or a short fiber. The cross-sectional shape of fiber (A) is not particularly limited, and examples include a circular, elliptical, irregular cross section, etc.

The fiber (A) may be a composite fiber or a monocomponent fiber. The composite fiber preferably has two or more thermoplastic resins as its constituent components. Examples of composite fibers include core-sheath type, side-by-side type, sea-island type, and parallel type.

The content of fiber (A) is appropriately selected depending on the application of the nonwoven fabric, and may be 10% to 90% by mass, 25% to 75% by mass, or 40% to 60% by mass relative to the total amount of the nonwoven fabric. The fiber may consist of only fiber (A).

(1.1.1.1) 4-methyl-1-pentene polymer (A)
The fiber (A) contains a 4-methyl-1-pentene polymer (A). The fiber (A) may consist only of the 4-methyl-1-pentene polymer (A). The melting point of the 4-methyl-1-pentene polymer (A) is usually 200° C. or higher. Therefore, when the fiber (A) contains the 4-methyl-1-pentene polymer (A), the heat resistance of the nonwoven fabric is excellent.

The 4-methyl-1-pentene polymer (A) is a homopolymer of 4-methyl-1-pentene, or a copolymer of 4-methyl-1-pentene and an olefin other than 4-methyl-1-pentene. The copolymer is preferably a random copolymer. From the viewpoint of obtaining a nonwoven fabric having excellent mechanical strength and a small average fiber diameter, the 4-methyl-1-pentene polymer (A) is preferably a homopolymer of 4-methyl-1-pentene.

The 4-methyl-1-pentene polymer (A) preferably contains 90 mol % to 100 mol % of structural units derived from 4-methyl-1-pentene and 0 to 10 mol % of structural units derived from an olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene, which provides a nonwoven fabric with more excellent heat resistance and mechanical properties.
The amount of the constituent units derived from 4-methyl-1-pentene is preferably from 95 mol % to 100 mol %, and more preferably from 97 mol % to 100 mol %, based on the total amount of the constituent units of the 4-methyl-1-pentene polymer (A).
The amount of structural units derived from an olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene is preferably 0 mol % to 5 mol %, more preferably 0 mol % to 3 mol %, based on the total amount of structural units of the 4-methyl-1-pentene polymer (A).

Examples of α-olefins having 2 to 20 carbon atoms that can be copolymerized components include ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. Particularly preferred α-olefins having 2 to 20 carbon atoms are 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. The copolymer may contain not only one type of these olefins but also two or more types of copolymerized olefins.
The 4-methyl-1-pentene and α-olefin used as the copolymerization raw materials for the 4-methyl-1-pentene polymer (A) may be derived from biomass.

The 4-methyl-1-pentene polymer (A) can be produced using a stereospecific catalyst. Examples of stereospecific catalysts include magnesium-supported titanium catalysts and metallocene catalysts. The 4-methyl-1-pentene polymer (A) can be obtained by polymerizing or copolymerizing the 4-methyl-1-pentene alone or 4-methyl-1-pentene with an olefin having 2 to 20 carbon atoms other than 4-methyl-1-pentene in the presence of a catalyst described in, for example, International Publication WO 01/53369, International Publication WO 01/27124, JP-A-3-193796, or JP-A-02-41303.

The 4-methyl-1-pentene polymer (A) may contain known compounding agents (e.g., antioxidants, heat stabilizers, weather stabilizers, etc.) to the extent that the object of the present disclosure is not impaired. The 4-methyl-1-pentene polymer (A) may be granulated or pulverized by known methods before use. Examples of the granulation or pulverization method include a method using a V-blender, ribbon blender, Henschel mixer, or tumbler blender. Examples of the granulation or pulverization method include a method in which the materials are mixed in the blender and then melt-kneaded in a device (e.g., a single-screw extruder, a double-screw extruder, a kneader, a Banbury mixer, etc.).

In order to obtain a nonwoven fabric having sufficient mechanical strength and a small average fiber diameter, the melt flow rate (MFR) of the 4-methyl-1-pentene polymer (A) is preferably 100 g/10 min to 500 g/10 min, more preferably 200 to 500 g/10 min. The melt flow rate (MFR) is measured under the conditions of a temperature of 260° C. and a load of 5 kg in accordance with ASTM D1238.
The MFR of the 4-methyl-1-pentene polymer (A) can be controlled by supplying hydrogen to the polymerization reaction system during polymerization of the polymer, thereby increasing the MFR value of the resulting 4-methyl-1-pentene polymer (A). The MFR value can be increased by melt-kneading the 4-methyl-1-pentene polymer (A) obtained by the polymerization reaction, or by further adding a peroxide and melt-kneading, and the MFR value can be controlled by appropriately combining these methods.

The molecular weight distribution (Mw/Mn) of the 4-methyl-1-pentene polymer (A) is preferably 2-10, more preferably 2-8, and further preferably 2-5.
The molecular weight distribution (Mw/Mn) of the 4-methyl-1-pentene polymer (A) is determined from the molecular weight (weight average molecular weight Mw, number average molecular weight Mn) obtained by using gel permeation chromatography (GPC) (manufactured by Waters, alliance 2000 type) with a column made by Tosoh Corporation (GMH type) and o-dichlorobenzene as the mobile phase, and calibrating with polystyrene standards. The Mw/Mn of the 4-methyl-1-pentene polymer (A) can be controlled by the type of polymerization catalyst used, polymerization conditions, etc. In particular, by using a metallocene catalyst, it is possible to obtain a 4-methyl-1-pentene polymer (A) with a narrow Mw/Mn.

When the MFR and Mw/Mn of the 4-methyl-1-pentene polymer (A) are within the above ranges, excessive heating is not required to reduce the melt viscosity of the 4-methyl-1-pentene polymer (A) when it is spun into fiber (A), and this can improve productivity reductions caused by clogging of the spinning nozzle due to thermal decomposition of the polymer, thread breakage, and the generation of foreign matter (e.g., scorch marks, etc.), and allows a wide range of operating conditions to be set during spinning. Furthermore, because fluctuations in the melt viscosity can be suppressed, fibers with a uniform average fiber diameter can be obtained.

The crystallization temperature (Tc) of the 4-methyl-1-pentene polymer (A) is preferably 200°C to 225°C, more preferably 210°C to 225°C. When the crystallization temperature (Tc) of the 4-methyl-1-pentene polymer (A) is 200°C to 225°C, the processability of the nonwoven fabric is excellent. The crystallization temperature (Tc) of the 4-methyl-1-pentene polymer (A) is measured using a differential scanning calorimeter (DSC) by heating the 4-methyl-1-pentene polymer (A) to 300°C in air, holding the temperature for 5 minutes, and cooling at a rate of 20°C/min.

The melting point (Tm) of the 4-methyl-1-pentene polymer (A) is preferably 210°C to 245°C, more preferably 230°C to 245°C. The melting point (Tm) of the 4-methyl-1-pentene polymer (A) is measured in air at a heating rate of 20°C/min using a differential scanning calorimeter (DSC).

(1.1.2) Fiber (B)
The fibers may further include fibers (B) in addition to the fibers (A).

From the viewpoint of obtaining a nonwoven fabric having excellent filtration performance and structural strength, ΔTg(B) is preferably 0.8° C. or more, more preferably 1.0° C. or more, even more preferably 1.2° C. or more, and particularly preferably 1.45° C. or more. ΔTg(B) may be, for example, 5.0° C. or less. From these viewpoints, ΔTg(B) may be 0.8° C. to 5.0° C.
The method for measuring ΔTg(B) is the same as that described in the Examples.

The glass transition temperature (Tg) of the fiber (B) is, from the viewpoint of reducing the variation in the average fiber diameter and from the viewpoint of heat resistance, preferably 85° C. or higher, more preferably 90° C. or higher, even more preferably 100° C. or higher, particularly preferably 110° C. or higher, and even more preferably 125° C. or higher.
From the viewpoint of excellent spinning stability, the glass transition temperature (Tg) of the fiber (B) is preferably 170° C. or lower, more preferably 160° C. or lower, and even more preferably 150° C. or lower.
The glass transition temperature (Tg) of the fiber (B) is preferably 85°C to 170°C, more preferably 90°C to 170°C, even more preferably 100°C to 160°C, particularly preferably 110°C to 150°C, and even more preferably 125°C to 150°C.
The method for measuring ΔTg(B) is the same as that described in the Examples.

The average fiber diameter and CV value of fiber (B) may be the same as those of the fibers described above.

Fiber (B) may be a long fiber or a short fiber. The cross-sectional shape of fiber (B) is not particularly limited, and examples include a circular, elliptical, irregular cross section, etc.

The fiber (B) may be a composite fiber or a monocomponent fiber. The composite fiber preferably has two or more thermoplastic resins as its constituent components. Examples of composite fibers include core-sheath type, side-by-side type, sea-island type, and parallel type.

When the fibers further contain fiber (B), the content ratio of fiber (A) and the content ratio of fiber (B) are preferably within the following ranges.
The ratio of the resin composition A constituting the fiber (A) to the resin composition B constituting the fiber B (resin composition A:resin composition B) is not particularly limited and is preferably 90:10 to 90:10, more preferably 70:30 to 30:70, and even more preferably 50:50, in mass ratio.

(1.1.2.1) Amorphous thermoplastic resin (B)
The fiber (B) contains the amorphous thermoplastic resin (B). The fiber (B) may be composed only of the amorphous thermoplastic resin (B).

Examples of the amorphous thermoplastic resin (B) include cyclic olefin polymers (B-1), polycarbonate, polyarylate which is a copolymer of bisphenol A and terephthalic acid, polyphenylene ether, modified polyphenylene ether which is a polymer alloy of polyphenylene ether and polystyrene (including impact resistant polystyrene), polyvinyl chloride, polyphenylene sulfide, polyether sulfone, polyamide imide, polyether imide, and polyester carbonate.
Among these, from the viewpoint of achieving both excellent filter performance and structural strength and a low average fiber diameter, the amorphous thermoplastic resin (B) preferably contains a cyclic olefin polymer (B-1), and is preferably a cyclic olefin polymer (B-1).

(1.1.2.2) Cyclic olefin polymer (B-1)
The cyclic olefin polymer (B-1) is not particularly limited as long as it is a polymer containing a structural unit derived from a cyclic olefin compound.

The fibers contained in the nonwoven fabric may contain only the cyclic olefin polymer (B-1) as a resin, or may contain the cyclic olefin polymer (B-1) and other resins. Examples of other resins include thermoplastic resins.

From the viewpoint of heat resistance, the content of the cyclic olefin polymer (B-1) is preferably 50% by mass or more, more preferably 90% by mass or more, and even more preferably 99% by mass or more, based on the total amount of the resin.
The content of the cyclic olefin polymer (B-1) may be 100% by mass based on the total amount of the fibers.

Thermoplastic resins that may be contained in the fibers (B) are not particularly limited, and examples thereof include homopolymers or copolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, and 4-methyl-1-hexene; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyamides such as nylon-6, nylon-66, and polymetaxylene adipamide; polyvinyl chloride, polyimide, ethylene-vinyl acetate copolymer, polyacrylonitrile, polycarbonate, polystyrene, and ionomers. The thermoplastic resin may consist of one type or a mixture of two or more types.

Examples of α-olefin homopolymers or copolymers include ethylene-based polymers such as ethylene random copolymers, such as ethylene-propylene random copolymers, high-pressure low-density polyethylene, linear low-density polyethylene (LLDPE), high-density polyethylene, and ethylene-1-butene random copolymers; propylene-based polymers such as propylene random copolymers, such as polypropylene (propylene homopolymer), propylene-ethylene random copolymer, and propylene-1-butene random copolymer; poly-1-butene, poly-4-methyl-1-pentene, etc.

The amorphous thermoplastic resin (B) contains a cyclic olefin polymer (B-1), which contains at least one selected from a cyclic olefin copolymer (B-1-1) and a ring-opening polymer of a cyclic olefin compound (B-1-2). The cyclic olefin copolymer (B-1-1) preferably contains the following structural unit (a) and the following structural unit (b), and more preferably contains a cyclic olefin copolymer (B-1-1). This provides the nonwoven fabric with superior filtration performance and mechanical properties. Details of the structural unit (a) and the structural unit (b) will be described later.

(1.1.2.3) Cyclic olefin copolymer (B-1-1)
The cyclic olefin copolymer (B-1-1) is a copolymer containing a structural unit derived from a cyclic olefin compound and a structural unit derived from a compound other than a cyclic olefin compound. The cyclic olefin copolymer (B-1-1) is preferably a copolymer containing at least one structural unit selected from the group consisting of a structural unit derived from ethylene and a structural unit derived from an α-olefin, and a structural unit derived from a cyclic olefin compound. The cyclic olefin copolymer (B-1-1) is more preferably a copolymer containing a structural unit derived from ethylene or a structural unit derived from an α-olefin, and a structural unit derived from a cyclic olefin compound.

The cyclic olefin compound constituting the cyclic olefin copolymer (B-1-1) is not particularly limited, and examples thereof include the cyclic olefin monomers described in paragraphs 0037 to 0063 of WO 2006/118261.

From the viewpoint of obtaining a nonwoven fabric having small fiber diameter variation and small average fiber diameter, the cyclic olefin copolymer (B-1-1) preferably contains the structural unit (a) and the structural unit (b).
Structural unit (a): At least one structural unit derived from an olefin compound represented by the following general formula (I).
Structural unit (b): a structural unit derived from a cyclic olefin compound, which is at least one selected from the group consisting of a structural unit represented by the following general formula (II), a structural unit represented by the following general formula (III), and a structural unit represented by the following general formula (IV).

In the above general formula (I), R ³⁰⁰ is a hydrogen atom, or a linear or branched hydrocarbon group having 1 to 29 carbon atoms.

In the general formula (II), u is 0 or 1, v is 0 or a positive integer, and w is 0 or 1. R ⁶¹ to R ⁷⁸ as well as R ^a1 and R ^b1 may be the same or different from each other and are a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, or an aromatic hydrocarbon group having 6 to 20 carbon atoms. At least two of R ⁷⁵ to R ⁷⁸ may be bonded to each other to form a monocycle or polycycle. v is preferably an integer of 0 to 2, more preferably 0 or 1.

In the general formula (III), x and d are each independently 0 or an integer of 1 or more. y and z are each independently an integer of 0 to 2. R ⁸¹ to R ⁹⁹ may be the same or different from each other, and are a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group which is an alkyl group having 1 to 20 carbon atoms or a cycloalkyl group having 3 to 15 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or an alkoxy group. The carbon atom to which R ⁸⁹ and R ⁹⁰ are bonded may be bonded directly or via ^an alkylene group having 1 to 3 carbon atoms to the carbon atom to which R 93 is bonded or the carbon atom to which R ⁹¹ is bonded. When y=z=0, R ⁹² and R ⁹⁵ or R ⁹⁵ and R ⁹⁹ may be bonded to each other to form a monocyclic or polycyclic aromatic ring. x and d are each independently preferably an integer of 0 to 2, more preferably 0 or 1.

In the general formula (IV), R ¹⁰⁰ and R ¹⁰¹ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms, and f is in the range of 1≦f≦18.

From the viewpoint of obtaining a nonwoven fabric having excellent filter performance, the cyclic olefin polymer (B-1) preferably contains a cyclic olefin copolymer (B-1-1).
The cyclic olefin polymer (B-1) is composed of the structural unit (a) and the structural unit (b), and it is more preferable that the structural unit (b) contains a structural unit represented by the general formula (II).
The cyclic olefin polymer (B-1) more preferably contains the above-mentioned structural unit (a) and the following structural unit (c).
It is particularly preferred that the cyclic olefin polymer (B-1) consists solely of the above-mentioned structural unit (a) and the following structural unit (c).
Structural unit (c): a structural unit represented by the above general formula (II), in which u is 0 and v is 1.

The olefin compound, which is one of the copolymerization raw materials for the cyclic olefin copolymer (B-1-1), is a compound that forms the structural unit represented by the above general formula (I) by addition polymerization. Specifically, an olefin compound represented by the following general formula (Ia), which corresponds to the above general formula (I), is used.

In the above general formula (Ia), R ³⁰⁰ is a hydrogen atom or a linear or branched hydrocarbon group having 1 to 29 carbon atoms.

Examples of the olefin compound represented by the general formula (Ia) include ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 3-methyl-1-butene, 3-methyl-1-pentene, 3-ethyl-1-pentene, 4-methyl-1-pentene, 4-methyl-1-hexene, 4,4-dimethyl-1-hexene, 4,4-dimethyl-1-pentene, 4-ethyl-1-hexene, 3-ethyl-1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene. From the viewpoint of obtaining better heat resistance and mechanical properties, among these, ethylene and propylene are preferred as the olefin compound, and ethylene is more preferred. The olefin compound represented by the general formula (Ia) may be used alone or in combination of two or more.

When the total of the structural units constituting the cyclic olefin copolymer (B-1-1) is taken as 100 mol %, the proportion of the structural unit (a) derived from an olefin compound is preferably 5 mol % to 95 mol %, more preferably 20 mol % to 90 mol %, even more preferably 40 mol % to 80 mol %, and particularly preferably 50 mol % or more and 70 mol % or less.
The proportion of the structural unit (a) derived from an olefin compound can be measured by 13C-NMR.

The cyclic olefin compound, which is one of the copolymerization raw materials for the cyclic olefin copolymer (B-1-1), includes the cyclic olefin monomer represented by the general formula (IIa), the cyclic olefin monomer represented by the general formula (IIIa), and the cyclic olefin monomer represented by the general formula (IVa), which correspond to the structural unit represented by the general formula (II), the structural unit represented by the general formula (III), and the structural unit represented by the general formula (IV), respectively.

In the above general formula (IIa), u is 0 or 1, v is 0 or a positive integer, preferably an integer of 0 to 2, more preferably 0 or 1, w is 0 or 1, R ⁶¹ to R ⁷⁸ as well as R ^a1 and R ^b1 may be the same or different from one another and are a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, or an aromatic hydrocarbon group having 6 to 20 carbon atoms, and at least two of R ⁷⁵ to R ⁷⁸ may be bonded to each other to form a monocycle or polycycle.

From the viewpoint of obtaining a nonwoven fabric with small fiber diameter variation and average fiber diameter, it is preferable that the cyclic olefin compound, which is one of the copolymerization raw materials of the cyclic olefin copolymer (B-1-1), forms a structural unit represented by the above general formula (II) by addition polymerization. Specifically, it is preferable to use a cyclic olefin monomer represented by general formula (IIa) corresponding to the above general formula (II).

As the copolymerization raw materials for the cyclic olefin copolymer (B-1-1), it is preferable to use only the olefin compound represented by general formula (Ia) and the cyclic olefin compound represented by general formula (IIa). From the viewpoint of obtaining a nonwoven fabric with excellent filter performance, it is more preferable to use only the olefin compound represented by general formula (Ia) and the cyclic olefin compound represented by general formula (IIa) where u is 0 and v is 1.

In the above general formula (IIIa), x and d are each independently 0 or an integer of 1 or more, preferably an integer of 0 to 2, and more preferably 0 or 1; y and z are each independently 0, 1, or 2; R ⁸¹ to R ⁹⁹ may be the same or different from one another and are a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group which is an alkyl group having 1 to 20 carbon atoms or a cycloalkyl group having 3 to 15 carbon atoms, an aromatic hydrocarbon group or an alkoxy group having 6 to 20 carbon atoms; the carbon atom to which R ⁸⁹ and R ⁹⁰ are bonded may be bonded directly or via an alkylene group having 1 to ³ carbon atoms to the carbon atom to which R ⁹³ is bonded or the carbon atom to which R 91 is bonded, and when y=z=0, R ⁹⁵ and R ⁹² or R ⁹⁵ and R ⁹⁹ may be bonded to each other to form a monocyclic or polycyclic aromatic ring.

In the above general formula (IVa), R ¹⁰⁰ and R ¹⁰¹ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms, and f is 1≦f≦18.

As the copolymerization components, it is preferable to use the olefin compound represented by the above-mentioned general formula (Ia) and the cyclic olefin monomer represented by the general formula (IIa), the cyclic olefin monomer represented by the general formula (IIIa), or the cyclic olefin monomer represented by the general formula (IVa). This further improves the solubility of the cyclic olefin copolymer (B-1-1) in the solvent, resulting in good moldability.

Specific examples of the cyclic olefin monomer represented by general formula (IIa), the cyclic olefin monomer represented by general formula (IIIa), and the cyclic olefin monomer represented by general formula (IVa) include the compounds described in paragraphs 0037 to 0063 of WO 2006/118261. Specific examples include bicyclo-2-heptene derivatives (bicyclohept-2-ene derivatives), tricyclo-3-decene derivatives, tricyclo-3-undecene derivatives, tetracyclo-3-dodecene derivatives, pentacyclo-4-pentadecene derivatives, pentacyclopentadecadiene derivatives, pentacyclo-3-pentadecene derivatives, pentacyclo-4-hexadecene derivatives, pentacyclo-3-hexadecene derivatives, hexacyclo-4-heptadecene derivatives, and heptacyclo-5-eicosene derivatives. Conductors, heptacyclo-4-eicosene derivatives, heptacyclo-5-heneicosene derivatives, octacyclo-5-docosene derivatives, nonacyclo-5-pentacosene derivatives, nonacyclo-6-hexacosene derivatives, cyclopentadiene-acenaphthylene adducts, 1,4-methano-1,4,4a,9a-tetrahydrofluorene derivatives, 1,4-methano-1,4,4a,5,10,10a-hexahydroanthracene derivatives, and cycloalkylene derivatives with 3 to 20 carbon atoms.

Among the cyclic olefin monomers represented by general formula (IIa), the cyclic olefin monomers represented by general formula (IIIa), and the cyclic olefin monomers represented by general formula (IVa), the cyclic olefin monomers represented by general formula (IIa) are preferred.

As the cyclic olefin monomer represented by the above general formula (IIa), it is preferable to use bicyclo[2.2.1]-2-heptene (also called norbornene) or tetracyclo[4.4.0.12,5.17,10]-3-dodecene (also called tetracyclododecene), and it is more preferable to use tetracyclo[4.4.0.12,5.17,10]-3-dodecene. These cyclic olefin monomers have the advantage that the elastic modulus of the copolymer is easily maintained because they contain a rigid ring structure.

When the total of the structural units constituting the cyclic olefin copolymer (B-1-1) is taken as 100 mol %, the proportion of the structural unit (b) is preferably 5 mol % to 95 mol %, more preferably 10 mol % to 80 mol %, further preferably 20 mol % to 60 mol %, and particularly preferably 30 mol % to 50 mol %.
The proportion of the structural unit (b) can be measured by 13C-NMR.

The type of copolymer of the cyclic olefin copolymer (B-1-1) is not particularly limited, and examples include random copolymers and block copolymers. In the present disclosure, it is preferable to use a random copolymer as the cyclic olefin copolymer (A-1) from the viewpoint of obtaining high-precision optical components having excellent optical properties such as transparency, refractive index, and birefringence.

As the cyclic olefin copolymer (B-1-1), a random copolymer of ethylene and tetracyclo[4.4.0.12,5.17,10]-3-dodecene and a random copolymer of ethylene and bicyclo[2.2.1]-2-heptene are preferred, and a random copolymer of ethylene and tetracyclo[4.4.0.12,5.17,10]-3-dodecene is more preferred.

The cyclic olefin copolymer (B-1-1) may be used alone or in combination of two or more kinds.
The monomers used as the copolymerization raw materials for the cyclic olefin copolymer (B-1-1) may be derived from biomass.

The cyclic olefin copolymer (B-1-1) can be produced by appropriately selecting the conditions according to the methods described in, for example, JP-A-60-168708, JP-A-61-120816, JP-A-61-115912, JP-A-61-115916, JP-A-61-271308, JP-A-61-272216, JP-A-62-252406, and JP-A-62-252407.

The content of the cyclic olefin copolymer (B-1-1) is preferably 80% by mass to 100% by mass, more preferably 80% by mass to 99% by mass, even more preferably 90% by mass to 99% by mass, and particularly preferably 95% by mass to 99% by mass, based on the total amount of fibers contained in the nonwoven fabric.

The glass transition temperature (Tg) of the cyclic olefin copolymer (B-1-1) is preferably 85° C. or higher, more preferably 90° C. or higher, even more preferably 100° C. or higher, particularly preferably 110° C. or higher, and even more preferably 125° C. or higher, from the viewpoints of reducing the variation in average fiber diameter and heat resistance.
The glass transition temperature (Tg) of the cyclic olefin copolymer (B-1-1) is preferably 170° C. or lower, more preferably 160° C. or lower, and even more preferably 150° C. or lower, from the viewpoint of excellent spinning stability.
The glass transition temperature (Tg) of the cyclic olefin copolymer (B-1-1) is preferably 85°C to 170°C, more preferably 90°C to 170°C, even more preferably 100°C to 160°C, particularly preferably 110°C to 150°C, and even more preferably 125°C to 150°C.
The glass transition temperature (Tg) of the cyclic olefin copolymer (B-1-1) can be measured using a differential scanning calorimeter (DSC). For example, using an RDC220 manufactured by SII Nano Technology, the glass transition temperature can be measured by increasing the temperature from room temperature to 200°C at a heating rate of 10°C/min under a nitrogen atmosphere, holding the temperature for 5 minutes, then lowering the temperature to 30°C at a heating rate of 10°C/min, holding the temperature for 5 minutes, and then raising the temperature to 200°C at a heating rate of 10°C/min.
When the glass transition temperature of the cyclic olefin copolymer (B-1-1) is measured using a nonwoven fabric, the nonwoven fabric may be melted to form a resin mass, and then the glass transition temperature may be measured.
When multiple glass transition temperatures are observed, the effects of the present disclosure are preferably achieved if at least one of the glass transition temperatures satisfies the above-mentioned numerical range of the glass transition temperature.

(1.1.2.4) Ring-opening polymer of cyclic olefin (B-1-2)
The cyclic olefin polymer (B-1) may be a ring-opened polymer (B-1-2) of a cyclic olefin. Examples of the ring-opened polymer (B-1-2) of a cyclic olefin include a ring-opened polymer of a norbornene monomer, a ring-opened polymer of a norbornene monomer and another monomer capable of ring-opening copolymerization with the norbornene monomer, and hydrogenated products thereof.

Examples of norbornene monomers include bicyclo[2.2.1]hept-2-ene (also called norbornene) and its derivatives (containing a substituent on the ring), tricyclo[4.3.01,6.12,5]deca-3,7-diene (also called dicyclopentadiene) and its derivatives, 7,8-benzotricyclo[4.3.0.12,5]deca-3-ene (also called methanotetrahydrofluorene: 1,4-methano-1,4,4a,9a-tetrahydrofluorene) and its derivatives, tetracyclo[4.4.0.12,5.17,10]-3-dodecene (also called tetracyclododecene) and its derivatives, etc.

Substituents on the rings of these derivatives include alkyl groups, alkylene groups, vinyl groups, alkoxycarbonyl groups, and alkylidene groups. The number of substituents may be one or more. Examples of derivatives containing substituents on such rings include 8-methoxycarbonyl-tetracyclo[4.4.0.12,5.17,10]dodec-3-ene, 8-methyl-8-methoxycarbonyl-tetracyclo[4.4.0.12,5.17,10]dodec-3-ene, and 8-ethylidene-tetracyclo[4.4.0.12,5.17,10]dodec-3-ene.

These norbornene monomers may be used alone or in combination of two or more. A ring-opening polymer of a norbornene monomer, or a ring-opening polymer of a norbornene monomer and another monomer capable of ring-opening copolymerization with the norbornene monomer, may be obtained by polymerizing the monomer components in the presence of a known ring-opening polymerization catalyst.

Examples of the ring-opening polymerization catalyst that can be used include catalysts consisting of a halide of a metal such as ruthenium or osmium, a nitrate or an acetylacetone compound, and a reducing agent; and catalysts consisting of a halide of a metal such as titanium, zirconium, tungsten, or molybdenum, or an acetylacetone compound, and an organoaluminum compound. Examples of other monomers that can be ring-opened copolymerized with norbornene monomers include monocyclic olefin monomers such as cyclohexene, cycloheptene, and cyclooctene.

Hydrogenated ring-opening polymers of norbornene-based monomers and hydrogenated ring-opening polymers of norbornene-based monomers and other monomers capable of ring-opening copolymerization with them can usually be obtained by adding a known hydrogenation catalyst containing a transition metal such as nickel or palladium to a polymerization solution of the ring-opening polymer and hydrogenating the carbon-carbon unsaturated bonds.

The ring-opening polymer (B-1-2) of a cyclic olefin may be used alone or in combination of two or more.

The ring-opening polymer of cyclic olefin (B-1-2) can be produced by appropriately selecting the conditions according to the methods described in, for example, JP-A-60-26024, JP-A-9-268250, JP-A-63-145324, and JP-A-2001-72839.

(1.1.3) Additives The fibers contained in the nonwoven fabric may contain commonly used additives as necessary. Examples of the additives include various known additives such as antioxidants, weathering stabilizers, heat stabilizers, light stabilizers, antistatic agents, antifogging agents, lubricants, dyes, pigments, natural oils, synthetic oils, and waxes.
From the viewpoint of reducing the variation in average fiber diameter and the average fiber diameter, the fibers contained in the nonwoven fabric preferably contain an antioxidant and a lubricant.

The following are examples of methods for kneading the cyclic olefin polymer (B-1) and the additives. When the cyclic olefin polymer (B-1) and the additives each have either a melting point or a glass transition temperature, known methods include a method in which the cyclic olefin polymer (B-1) and the additives are mixed in a mixer tumbler or the like at a temperature below the melting point or the glass transition temperature, and then the mixture is fed to the hopper of a molding machine, a method in which the cyclic olefin polymer (B-1) and the additives are mixed using a mixing feeder or the like while feeding them to an extruder, and a method of side-feeding to an extruder hopper, etc.

(1.1.3.1) Antioxidants As the antioxidants, phenol-based antioxidants, phosphorus-based stabilizers, sulfur-based stabilizers and ultraviolet absorbers have an antioxidant effect on the heat-molten cyclic olefin polymer (B-1).

Examples of the antioxidant include phenol-based antioxidants, phosphorus-based antioxidants, and sulfur-based antioxidants.
Examples of phenol-based antioxidants include octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], and pentaerythrityl tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].
Examples of phosphorus-based antioxidants include triphenyl phosphite, tris(cyclohexylphenyl)phosphite, and 9,10-dihydro-9-oxa-10-phosphaphenanthrene.
Examples of the sulfur-based antioxidants include dimyristyl 3,3'-thiodipropionate, distearyl-3,3'-thiodipropionate, laurylstearyl-3,3'-thiodipropionate, pentaerythritol-tetrakis(β-lauryl-thiopropionate), and the like.
These antioxidants may be used alone or in combination of two or more. Among these, it is preferable to use a phenol-based antioxidant.

In the fibers contained in the nonwoven fabric, the content of the antioxidant is preferably 0.01 to 0.4 parts by mass, more preferably 0.02 to 0.3 parts by mass, even more preferably 0.02 to 0.2 parts by mass, particularly preferably 0.02 to 0.1 parts by mass, and even more preferably 0.02 to 0.08 parts by mass, based on 100 parts by mass of the cyclic olefin polymer (B-1).
When the content of the antioxidant is 0.01 part by mass or more, the occurrence of scorching on the molded article tends to be suppressed.
By setting the content of the antioxidant to 0.4 parts by mass or less, it is possible to suppress a decrease in the rejection rate of fine particles, elution of the antioxidant from the molded article, and the like.

(1.1.3.2) Lubricant The lubricant preferably contains a functional group such as a hydroxyl group, a carboxyl group, an oxyalkylene group, an ester group, an amino group, an amide group, a sulfo group, an epoxy group, an acid anhydride group, an acid metal salt, a phosphono group, a phosphino group, or a silyl group. When a lubricant containing the above-mentioned functional group is used in combination with a cyclic olefin polymer (B-1), the lubricant begins to dissolve before the cyclic olefin polymer (B-1) during molding, so that the pressure and shear force applied to the cyclic olefin polymer (B-1) can be suppressed. As a result, there is a tendency that the variation in the average fiber diameter during spinning can be suitably suppressed.

The lubricant may contain two or more functional groups. When the lubricant contains two or more functional groups, they may contain different types of functional groups or the same type of functional groups. The lubricant may be a compound containing a structure in which at least one of the functional groups is bonded to a carbon atom of a linear hydrocarbon group, or a compound containing a structure in which the functional group is bonded to a carbon atom of a linear hydrocarbon group and the functional group is bonded to at least one other carbon atom of the linear hydrocarbon group. Among the functional groups, amide groups and silyl groups are preferred, and amide groups are more preferred.

Examples of the lubricant include fatty acid amides, fatty acid metal salts, and silicone compounds.
Examples of the fatty acid amide include fatty acid monoamides, fatty acid diamides, saturated fatty acid monoamides, unsaturated fatty acid diamides, etc. Specific examples of the fatty acid amides include lauric acid amide, myristic acid amide, palmitic acid amide, stearic acid amide, behenic acid amide, oleic acid amide, erucic acid amide, montanic acid amide, methylene bislauric acid amide, methylene bismyristic acid amide, methylene bispalmitic acid amide, methylene bisstearic acid amide, ethylene bisstearic acid amide, methylene bisbehenic acid amide, methylene bisoleic acid amide, methylene biserucic acid amide, ethylene bisoleic acid amide, ethylene biserucic acid amide, etc.
Examples of fatty acid metal salts include zinc stearate, calcium stearate, magnesium stearate, lithium stearate, sodium stearate, calcium 12-hydroxystearate, zinc 12-hydroxystearate, sodium 12-hydroxystearate, zinc montanate, sodium montanate, etc. Examples of silicone compounds include alkyl silicon alkoxides such as methyltrimethoxysilane and dimethyldimethoxysilane, silylated polyolefins, etc. As the silylated polyolefin, any compound containing a silicone portion and a polyolefin portion may be used, and for example, the compounds described in paragraphs 0025 to 0032 of JP 2017-39892 A can be used.

In the fibers contained in the nonwoven fabric, the content of the lubricant is preferably 0.005 parts by mass to 0.4 parts by mass, more preferably 0.01 parts by mass to 0.4 parts by mass, even more preferably 0.02 parts by mass to 0.3 parts by mass, particularly preferably 0.02 parts by mass to 0.2 parts by mass, and even more preferably 0.02 parts by mass to 0.1 parts by mass, based on 100 parts by mass of the cyclic olefin polymer (B-1).
When the content of the lubricant is 0.01 part by mass or more, the variation in the average fiber diameter tends to be more suitably suppressed.
By keeping the content of the lubricant at 0.4 parts by mass or less, there is a tendency that a decrease in the rejection rate of fine particles and elution of the lubricant from the molded article can be suppressed.

By combining the cyclic olefin polymer (B-1) with an antioxidant and a lubricant, the stability during spinning is further improved, and the variation in the average fiber diameter and the average fiber diameter can be suitably reduced. In particular, by setting the content of the antioxidant to 0.01 parts by mass to 0.4 parts by mass per 100 parts by mass of the cyclic olefin polymer (B-1) and the content of the lubricant to 0.005 parts by mass to 0.4 parts by mass per 100 parts by mass of the cyclic olefin polymer (B-1), the effects of the present disclosure are more suitably achieved. The contents of the antioxidant and the lubricant may be appropriately combined within the aforementioned numerical ranges.

(2) Filter The filter of the present disclosure includes the nonwoven fabric of the present disclosure. As a result, the filter of the present disclosure has excellent heat resistance, filtering performance, and structural strength.

Examples of filters include bag filters, dust collection filters, air cleaners, hollow fiber filters, water purification filters, etc. Among these, it is preferable that the filter be a bag filter, since nonwoven fabric has excellent heat resistance.

The structure of the filter is appropriately selected depending on the application of the filter, and may be a single-layer structure or a multi-layer structure of two or more layers. When the filter has a multi-layer structure, the filter may include multiple nonwoven fabrics of the present disclosure.

(3) Prepreg The prepreg of the present disclosure includes the nonwoven fabric of the present disclosure and a resin composition containing at least one of a thermosetting resin and a thermoplastic resin. Since the prepreg of the present disclosure includes the nonwoven fabric of the present disclosure, the prepreg of the present disclosure has excellent heat resistance when the resin composition is cured or solidified.

From the viewpoint of providing a prepreg with superior heat resistance when cured or solidified, the prepreg of the present disclosure has a thermal expansion coefficient at 50°C to 100°C of preferably 50 ppm/°C or less, more preferably 40 ppm/°C or less, of the cured product obtained by heating at 145°C for 10 minutes and curing, or of the solidified product cooled at room temperature (23°C).

From the viewpoint of being more excellent when used as an insulating layer in a printed wiring board described below, the prepreg of the present disclosure preferably has a dielectric tangent value at 1 GHz when cured of 0.005 or less, and more preferably 0.001 or less.
The method for adjusting the dielectric tangent value to be within the above range is not particularly limited, and examples thereof include a method of decreasing the moisture content and a method of decreasing the fiber diameter.

The method for producing the prepreg is not particularly limited, and known production methods can be applied. For example, the method for producing the prepreg includes a production method including a step of impregnating a nonwoven fabric of the present disclosure with a varnish containing a resin composition to obtain an impregnated body, and a step of heating the obtained impregnated body to remove the solvent contained in the varnish and dry it.

Impregnation of the nonwoven fabric of the present disclosure with a varnish containing the above-mentioned resin composition can be carried out, for example, by applying a predetermined amount of varnish to the nonwoven fabric of the present disclosure, further layering a protective film on top of it as necessary, and pressing from above with a roller or the like. Examples of application methods include spray coating, dip coating, roll coating, curtain coating, die coating, and slit coating.

The method of heating the impregnated body to dry the solvent contained in the varnish is not particularly limited, and examples include a batch method in which the impregnated body is dried in an air or nitrogen atmosphere using a blower dryer, and a continuous process in which the impregnated body is dried through a heating furnace.

Thermosetting resins include epoxy resins, melamine resins, phenolic resins, unsaturated polyester resins, silicone resins, etc. Among the above, it is preferable that the thermosetting resin contains an epoxy resin. The thermosetting resin may be a single type or a combination of two or more types. From the viewpoint of forming a prepreg having excellent heat resistance when cured, it is preferable that the curable resin is a thermosetting resin having a curing temperature that is 20°C or more lower than the lowest melting point of the nonwoven fabric.

Thermoplastic resins include the same thermoplastic resins as those exemplified in the other thermoplastic resins described above. The thermoplastic resin may be a single type, or a combination of two or more types. From the viewpoint of forming a prepreg having excellent heat resistance when solidified, the thermoplastic resin is preferably a thermoplastic resin having a melting point that is 20°C or more lower than the lowest melting point of the nonwoven fabric.

The thickness of the prepreg can be appropriately selected depending on the intended use. For example, from the viewpoint of improving the formability when laminating the prepreg, the mechanical strength and toughness of the cured product, etc., the thickness of the prepreg is preferably 0.001 mm to 10 mm, more preferably 0.005 mm to 1 mm, and even more preferably 0.01 mm to 0.5 mm.

The uses of the prepreg disclosed herein are not particularly limited, and it can be used, for example, in printed wiring boards, etc., as described below.

(4) Conductor Laminate The conductor laminate of the present disclosure includes the prepreg of the present disclosure and a conductor layer laminated on at least one surface of the prepreg. The conductor laminate of the present disclosure has the above-mentioned configuration and is therefore excellent in heat resistance.

The conductor layer is not particularly limited as long as it is a layer containing a material having electrical conductivity, and a metal foil is preferable. Examples of metal foil include copper foil, aluminum foil, nickel foil, gold foil, silver foil, stainless steel foil, etc. The conductor laminate of the present disclosure can be manufactured by a known manufacturing method.

(5) Printed Wiring Board The printed wiring board of the present disclosure comprises a cured or solidified product of the prepreg of the present disclosure, and a conductor layer that is disposed on one or both sides of the cured or solidified product and that has been subjected to wiring processing. The printed wiring board of the present disclosure has the above-mentioned configuration and is therefore excellent in heat resistance.

The printed wiring board may have a conductor layer with wiring on one or both sides of a laminate formed by stacking the cured or solidified prepreg of the present disclosure.

The printed wiring board may have a conductor layer with antenna circuit processing on one or both sides of the cured or solidified prepreg of the present disclosure.

The method for producing the printed wiring board is not particularly limited, and known production methods can be applied. For example, in the method for producing the printed wiring board, the prepreg produced by the above-mentioned method is heated and cured by a lamination press or the like to form an insulating layer. Next, a conductor layer is laminated on the obtained insulating layer by a known method to produce a laminate. Thereafter, the conductor layer in the laminate is subjected to circuit processing or the like to obtain a printed wiring board.

Metals are suitable for the conductor layer. Examples of metals that can be used include copper, aluminum, nickel, gold, silver, and stainless steel. Methods for forming the conductor layer include, for example, a method in which a conductive material such as a metal is made into a foil and heat-sealed to an insulating layer; a method in which an insulating layer and a conductor layer are bonded together using an adhesive; and a method in which a conductor layer is formed by sputtering, vapor deposition, plating, or the like. The printed wiring board may be either a single-sided board or a double-sided board.
The printed wiring board of the present disclosure can be used as an electronic component by mounting electronic components such as semiconductor elements thereon.

(6) Electronic Component The electronic component of the present disclosure is an electronic component having a circuit for transmitting an electrical signal of 1 GHz or more, and has an insulating layer containing a cured or solidified product of the prepreg of the present disclosure. Due to the above configuration, the electronic component of the present disclosure has excellent heat resistance.

Electronic components can be manufactured based on known methods. Examples of electronic components having circuits that transmit electrical signals of 1 GHz or more include high-frequency antenna circuits, backplanes of high-speed servers and routers, flexible boards for high-speed transmission used in hard disks, liquid crystal displays, etc., radar components, etc.

(7) Manufacturing method of nonwoven fabric The manufacturing method of the nonwoven fabric of the present disclosure is not particularly limited, and it is preferable to use a spunbond method. Hereinafter, a manufacturing method of a nonwoven fabric by the spunbond method in the case where the nonwoven fabric of the present disclosure is a mixed fiber nonwoven fabric will be described.

The method for producing a nonwoven fabric according to the present disclosure includes a web-forming step and a dividing step, which are carried out in this order.
This results in a nonwoven fabric that is a spunbonded nonwoven fabric composed of a plurality of fibers having an average fiber diameter smaller than that of fibers produced by a normal spunbonding method.

(7.1) Web Forming Step In the web forming step, the 4-methyl-1-pentene polymer (A) and the amorphous thermoplastic resin (B) are melted separately in an extruder, and each melt is discharged from a spinneret having a composite spinning nozzle to spin out a plurality of split fibers. This produces a web consisting of a plurality of split fibers. The split fibers contain at least one solidified product of the 4-methyl-1-pentene polymer (A) and at least one solidified product of the amorphous thermoplastic resin (B).

The extruder is not particularly limited and may be a single-screw extruder or a multi-screw extruder. The resin fed from the hopper may be melted in the compression section of the extruder.

The spinneret is disposed at the tip of the extruder. The spinneret has multiple composite spinning nozzles. The spinneret having the composite spinning nozzles has a structure in which the 4-methyl-1-pentene polymer (A) and the amorphous thermoplastic resin (B) are each arranged radially, in parallel, or in a row in the longitudinal cross section of the split fiber. For example, the multiple spinning nozzles may be arranged in a row.

Spinnerets 10A-10I, which are examples of spinnerets having composite spinning nozzles, are shown in Figures 1(a)-1(i). As shown in Figures 1(a)-1(i), spinnerets 10A-10I have multiple spinning nozzles 11 and multiple spinning nozzles 12. A melt of 4-methyl-1-pentene polymer (A) is supplied to spinning nozzle 11, and a melt of amorphous thermoplastic resin (B) is supplied to spinning nozzle 12.

The diameter of the spinning nozzle is preferably 0.1 mm to 2.0 mm. The molten resin is transported to the spinneret by the extruder and introduced into the spinning nozzle. The fibrous molten resin is discharged from the opening of the spinning nozzle. The discharge pressure of the molten resin is preferably in the range of 0.01 kgf/cm ² to 200 kgf/cm ^2. This allows the discharge rate to be increased, enabling mass production of nonwoven fabrics.

In this case, taking into consideration the decomposition of the 4-methyl-1-pentene polymer (A) and the amorphous thermoplastic resin (B), it is preferable that the melting temperatures of these resins are in the range of 20 to 100°C higher than the higher of the melting point of the 4-methyl-1-pentene polymer (A) and the glass transition temperature of the amorphous thermoplastic resin (B).

The spun split fibers are cooled with a cooling fluid such as air, and then tension is applied to the long fibers with a fluid such as stretching air to thin them to a specified fineness, and they are then deposited as is on a collection belt to a specified thickness. Note that the cooling fluid and the fluid used to apply tension to the split fibers to thin them may be the same or different.

The speed (air volume) of the stretching air is preferably 1000 Nm ³ /h/m to 10000 Nm ³ /h/m, more preferably 2000 Nm ³ /h/m to 6000 Nm ³ /h/m. This allows the production of a nonwoven fabric with excellent texture. The temperature of the stretching air is usually 5°C to 100°C or less, preferably in the range of 15°C to 50°C.
In this case, it is necessary to orient and crystallize the 4-methyl-1-pentene polymer (A) or orient the amorphous thermoplastic resin (N) by appropriately selecting the molding temperature, spinning speed, and cooling air temperature within a range in which spinnability is good. The oriented crystallization of the 4-methyl-1-pentene polymer (A) and the orientation of the amorphous thermoplastic resin referred to here are evaluated from the difference in glass transition temperature observed from the first heating and the second heating in DSC measurement.

(7.2) Splitting step In the splitting step, stress is applied to the web made of split fibers. As a result, one split fiber is split into a plurality of fibers. More specifically, a solidified material of at least one 4-methyl-1-pentene polymer (A) contained in one split fiber becomes fiber (A). A solidified material of at least one amorphous thermoplastic resin (B) contained in one split fiber becomes fiber (B). In other words, a nonwoven fabric that is a mixed fiber nonwoven fabric is obtained.

The dividing process may be performed continuously after the web forming process is performed, or the dividing process does not have to be performed continuously after the web forming process is performed. Between the web forming process and the dividing process, other processes different from the web forming process and the dividing process may be performed.

The method of applying stress to the web is not particularly limited, and examples include a high-pressure liquid flow. When applying a high-pressure water flow to a web made of split fibers, it is preferable to replace the air present between adjacent split fibers that make up the web with water, for example, before the process of splitting and entangling the fibers using the high-pressure liquid flow, in order to promote entanglement. Specifically, water may be applied to the web.

The high-pressure liquid flow is obtained by passing the liquid through a nozzle hole and pressurizing it with a high-pressure pump, followed by spraying. The diameter of the nozzle hole is usually 0.05 mm to 1.0 mm, preferably 0.1 mm to 0.5 mm. The pressure of the high-pressure liquid flow is usually 50 kgf/cm ² to 600 kgf/cm ² , preferably 50 kgf/cm ² to 250 kgf/cm ² . The liquid is preferably water or hot water, from the viewpoint of ease of handling. The water or hot water is preferably pure water. The resistivity of the pure water measured by a known water quality measuring device is preferably 10 MΩ·cm or more, more preferably 15 MΩ·cm or more.

The distance between the nozzle hole and the web is preferably about 0.5 cm to 15 cm. If this distance exceeds 15 cm, the energy that the liquid imparts to the web decreases, and the effect of splitting and entangling the split fibers tends to decrease. If the distance between the nozzle hole and the web is less than 0.5 cm, the web formation tends to become disrupted.

In general, the nozzle holes of the high-pressure liquid stream are arranged in a row in a direction crossing the traveling direction of the web. When stress is applied to one side of the web, in order to obtain uniform division of the split fibers and tight intertwining, the number of rows in which the multiple injection holes are arranged is preferably two or more rows, more preferably three or more rows. It is preferable to make the pressure of the high-pressure liquid stream low on the front stage side and high on the rear stage side in order to uniformize the formation.
The number of times stress is applied to the web (hereinafter, "treatment number") is selected depending on the method of applying stress to the web, etc. When the method of applying stress to the web is a high-pressure liquid flow, the treatment number is preferably 2 to 8 times, more preferably 3 to 7 times, and further preferably 4 to 6 times.

The pattern of the nonwoven fabric can be changed by appropriately selecting the pattern of the screen belt used when processing the high-pressure liquid flow.

The nonwoven fabric that has been split by the high-pressure liquid flow is then mechanically squeezed to remove excess water, and then dried and heat-treated to become the final product. The heat treatment temperature and time can be selected not only to remove water, but also to allow for moderate shrinkage and promotion of crystallization. The heat treatment can be a dry heat treatment or a moist heat treatment.

The present disclosure will be explained in detail below using examples, but the present disclosure is not limited to the following examples as long as it does not deviate from the gist of the disclosure.

[1] Preparation [1.1] 4-methyl-1-pentene polymer (A)
[1.1.1] 4-Methyl-1-pentene polymer (A1)
As the 4-methyl-1-pentene polymer (A) in Examples 1 to 3 and Comparative Example 2, the following 4-methyl-1-pentene polymer (A1) was prepared.
4-Methyl-1-pentene polymer (A1): 4-methyl-1-pentene/decene-1 copolymer (decene-1 content: 3 mass%, melting point (Tm): 233° C., melt flow rate (MFR): 320 g/10 min, molecular weight distribution (Mw/Mn): 5, crystallization temperature (Tc): 214° C.)

[1.1.2] 4-Methyl-1-pentene polymer (A2)
As the 4-methyl-1-pentene polymer (A) of Comparative Example 1, the following 4-methyl-1-pentene polymer (A2) was prepared.
4-Methyl-1-pentene polymer (A2): 4-methyl-1-pentene/decene-1 copolymer (decene-1 content: 3 mass%, melting point (Tm): 233°C, melt flow rate (MFR): 500 g/10 min, molecular weight distribution (Mw/Mn): 3, crystallization temperature (Tc): 214°C)

[1.2] Cyclic olefin copolymer (B)
As the cyclic olefin copolymer (B), a cyclic olefin copolymer (B1) was prepared as follows.

[1.2.1] Preparation of catalyst VO( _OC2H5 ) _Cl2 was diluted with cyclohexane to prepare a cyclohexane solution of vanadium catalyst with a vanadium concentration of _6.7 mmol/L. Ethyl aluminum sesquichloride (Al( _C2H5 ) _1.5Cl1.5 ) was diluted with cyclohexane to prepare a cyclohexane solution of organoaluminum compound catalyst with an aluminum concentration of 107 mmol/L.

[1.2.2] Polymerization of Monomers Using a stirred polymerization vessel (inner diameter 500 mm, reaction volume 100 L), a copolymerization reaction of ethylene and tetracyclo[4.4.0.12,5.17,10]-3-dodecene was continuously carried out. Here, ethylene was supplied into the polymerization vessel together with hydrogen gas. Cyclohexane was used as the polymerization solvent. When carrying out the polymerization reaction, the cyclohexane solution of the vanadium catalyst prepared by the above method was supplied into the polymerization vessel so that the vanadium catalyst concentration relative to cyclohexane in the polymerization vessel was 0.6 mmol/L.
Furthermore, ethylaluminum sesquichloride, an organoaluminum compound, was fed into the polymerization vessel so that the mass ratio of aluminum to vanadium (Al/V) became 18.0. The copolymerization reaction was continuously carried out at a polymerization temperature of 8° C. and a polymerization pressure of 1.8 kg/cm ² G to obtain a copolymer of ethylene and tetracyclo[4.4.0.12,5.17,10]-3-dodecene (ethylene-tetracyclo[4.4.0.12,5.17,10]-3-dodecene copolymer).

[1.2.3] Removal of catalyst The polymerization reaction was terminated by adding water and a 25% by mass NaOH solution as a pH adjuster to the ethylene-tetracyclo[4.4.0.12,5.17,10]-3-dodecene copolymer solution withdrawn from the polymerization vessel. The catalyst residues present in the ethylene-tetracyclo[4.4.0.12,5.17,10]-3-dodecene copolymer were removed.

[1.2.4] Removal of unreacted monomers The above-mentioned cyclohexane solution of the copolymer with a concentration of 5% by mass was supplied at 150 kg/h to a ^double -tube humidifier (outer tube diameter 2B, inner tube diameter 3/4B, length 21 m) using steam at 20 kg/cm ^{2 G as a heat source, and heated to 180° C. Using steam at 25 kg/cm 2} G as a heat source, and a double-tube flash dryer (outer tube diameter 2B, inner tube diameter 3/4B, length 27 m) and a flash hopper (volume 200 L), most of the unreacted monomers were removed from the cyclohexane solution of the copolymer that had been subjected to the heating, together with cyclohexane, which was the polymerization solvent. As a result, a flash-dried cyclic olefin polymer (B1) in a molten state was obtained.

[1.2.5] Extrusion of resin The above-mentioned molten cyclic olefin polymer (B1) was charged into a vented twin-screw kneading extruder through the resin charging section. Then, in order to remove volatiles from the vent section, the extruder conditions were adjusted so that the difference between the maximum and minimum resin temperatures in the extruder diverter section was within 3°C while sucking with a vacuum pump through a trap. Then, pelletized with an underwater pelletizer attached to the extruder outlet, and the obtained pellets were dried with hot air at a temperature of 100°C for 4 hours. The glass transition temperature (Tg) of the cyclic olefin polymer (B1) constituting the pellets was measured by the method described below, and the Tg was 135°C.

[2] Examples and Comparative Examples [2.1] Example 1
Using 4-methyl-1-pentene polymer (A1) as the 4-methyl-1-pentene polymer (A), and cyclic olefin polymer (B1) as the amorphous thermoplastic resin, 4-methyl-1-pentene polymer (A1) was melted at a molding temperature of 310° C., and cyclic olefin polymer (B1) was melted at a molding temperature of 300° C. in separate extruders. Split fibers having a mass ratio of 4-methyl-1-pentene polymer (A1) and cyclic olefin polymer (B1) of 50/50 were spun using a splittable conjugate fiber spinning die having a cross ^- sectional shape as shown in FIG. 1( f) and having a total of 16 segments, at a spray gas speed (air volume) of 2240 Nm 3 /h/m and a throughput rate per hole of 0.6 g/min. The spun split fibers were stretched while being cooled with air (25° C.), and then deposited on a collecting belt to obtain a web. Next, in order to split the split fibers, a nozzle with a hole diameter of φ0.11 mm was used, and the distance from the nozzle to the web was set to 1 cm, and water jet processing was applied five times to the surface of the web at a water pressure of 100 kgf/ ^cm2 and a line speed of 4.3 m/min to produce a nonwoven fabric with a basis weight of 31 g/ ^m2 . When the obtained nonwoven fabric was examined under an electron microscope, it was confirmed that some of the split fibers had been split into multiple fibers, and that the nonwoven fabric was a mixed fiber nonwoven fabric.
The nonwoven fabric thus obtained was evaluated by measuring various data. The results are shown in Table 1.

[2.2] Examples 2 and 3
A nonwoven fabric was obtained in the same manner as in Example 1, except that the gas flow rate was changed as shown in Table 1.

[2.3] Comparative Example 1
The 4-methyl-1-pentene polymer (A2) was spun by a melt blowing method under conditions of a resin temperature of 345°C and a gas jet speed (air volume) of ⁴⁶⁵ Nm3/h/m, and the fibers were collected by a web former to obtain a nonwoven fabric. The average fiber diameter of the obtained fibers was 2.5 μm. The basis weight of the obtained nonwoven fabric was 30 g/ ^m2 .

[2.4] Comparative Example 2
The 4-methyl-1-pentene polymer (A1) was melted at a molding temperature of 310°C, and long fibers of the 4-methyl-1-pentene polymer (A1) were spun out at a gas jet speed (air volume) of 1600 ^Nm3 /h/m and a discharge rate per hole of 0.6 g/min. The spun long fibers were stretched while being cooled with air (25°C) and then deposited on a collecting belt. A nonwoven fabric was thus obtained. The average fiber diameter of the obtained fibers was 18 μm. The basis weight of the obtained nonwoven fabric was 30 g/ ^m2 .

[3] Measurement Methods The fiber properties of the nonwoven fabrics were measured as follows. The measurement results of Examples 1 to 3 and Comparative Examples 1 and 2 are shown in Table 1.

[3.1] Glass transition temperature Fibers were collected from the nonwoven fabric, and the collected fibers were used as samples. The extrapolated glass transition onset temperature of the samples was measured at a heating rate of 10°C/min using differential scanning calorimetry (DSC) in accordance with JIS K7121 (1987). The measured value of the extrapolated glass transition onset temperature was taken as the glass transition temperature (Tg).

[3.2] Glass transition temperature difference ΔTg
Fibers were collected from the nonwoven fabric, and the collected fibers were used as samples. Using DSC, the samples were melted by first heating at a heating rate of 10°C/min, then solidified by cooling at a heating rate of 10°C/min, and then melted by second heating at a heating rate of 10°C/min. In this case, the first glass transition temperature of the sample by the first heating and the second glass transition temperature of the sample by the second heating were measured in the same manner as in the above-mentioned glass transition temperature measurement method (in accordance with JIS K7121 (1987)). The value obtained by subtracting the measured value of the second glass transition temperature from the measured value of the first glass transition temperature was defined as the glass transition temperature difference ΔTg. The samples of Examples 1 to 3 contained two different types of fibers.

[3.3] Average fiber diameter and coefficient of variation (CV value)
A photograph of the nonwoven fabric was taken at a magnification of 1000 times using an electron microscope (Hitachi S-3500N). Fibers whose diameters could be measured were selected from the photograph, and the diameters of the selected fibers were measured. Imaging and measurement were repeated until the total number of fibers measured exceeded 100. The arithmetic mean value of the obtained fiber diameter measurements was taken as the average fiber diameter.
As shown in the following formula (1), the standard deviation (Dp) of the measurement results was divided by the average fiber diameter (Da) to obtain a value which was defined as the coefficient of variation (CV value) of the fiber diameter.
Formula (1): CV value = [standard deviation (Dp) / average fiber diameter (Da)] x 100

[3.4] Weight per unit area Three samples measuring 100 mm lengthwise x 100 mm widthwise were taken from the nonwoven fabric, and the mass of each sample was measured. The average value of the measurements was converted to a value per unit area, and the value obtained by rounding off to the first decimal place was taken as the weight per unit area (g/ ^m2 ).

[3.5] Thickness The thickness of the sample for which the basis weight was measured was measured at five points, namely, the center and the four corners of the main surface, using a thickness meter (manufactured by PEACOCK, product number "R1-250", measuring probe 25 mmφ) under a load of 7 g/ ^m2 . The thickness of three samples for which the basis weight was measured was measured by this method, and the average value was taken as the thickness (mm).

[3.6] Specific surface area The specific surface area of the nonwoven fabric is a value obtained in accordance with JIS Z8830:2013.

[3.7] Average and standard deviation of absorbance The average and standard deviation of absorbance of the nonwoven fabric were measured using a Fermentation Tester FMT-MIII manufactured by Nomura Shoji Co., Ltd. The average value of five arbitrary points was calculated and rounded off to the first decimal place.

[3.8] Collection efficiency The dust collection efficiency of the nonwoven fabric was measured by the following method. Three samples of 15 cm x 15 cm were taken from any part of the nonwoven fabric, and the collection efficiency of each sample was measured using a collection performance measuring device (Tokyo Dylec Co., Ltd., Model 8130). In measuring the collection efficiency, NaCl particle dust with a number median diameter of 0.3 μm was generated by an atomizer, and then the sample was set in a holder, and the air volume was adjusted with a flow control valve so that the filter passing speed was 5.3 cm/sec, and the dust concentration was stabilized in the range of 15 mg/m ³ to 20 mg/m ^3. The number median diameter refers to the diameter corresponding to a cumulative probability of 50% in the number distribution. The number of dust particles D2 upstream and the number of dust particles D1 downstream of the sample were detected by a laser particle detector, and the value obtained by the following formula (2) was rounded off to one decimal place to determine the collection efficiency. The arithmetic average of the collection efficiencies of the three samples was taken as the collection efficiency.
Equation (2): Collection efficiency = 1 - (D1/D2)
In formula (2), D1 represents the number of dust particles downstream, and D2 represents the number of dust particles upstream.

[3.9] Pressure loss The static pressure difference between the upstream and downstream of the sample during the measurement of the collection efficiency was read with a pressure gauge. The arithmetic mean value of the static pressure difference measurements of the three samples was taken as the pressure loss.

[3.10] Q value The Q value was calculated from the arithmetic mean value of the measured pressure loss of the nonwoven fabric and the arithmetic mean value of the measured pressure loss using formula (a).

[3.11] Structural strength A sample of 50 mm wide x 200 mm long was taken from the nonwoven fabric. Using a tensile tester, the tensile strength (MD) of the sample in the MD (fiber flow direction) was measured at five points with a chuck distance of 100 mm and a head speed of 300 mm/min. The average value of the five tensile strengths (MD) was taken as the structural strength (N/50 mm).
The acceptable range for structural strength is 8N/50mm or greater.

[3.12] Formation index The formation index of five arbitrary points of the nonwoven fabric was measured using a formation tester (Nomura Shoji Co., Ltd., Formation Tester FMT-MIII). The average value of the five measured formation indexes was rounded off to the first decimal place to obtain the formation index.
The formation index (V) is expressed by the following formula (2).
Formula (2): V=10σ/E
In formula (2), σ is the standard deviation of the unevenness in shading of the nonwoven fabric, and E is a value calculated from the light transmittance (T [%]) of the nonwoven fabric by E = 2-log T. When the light transmittance of the nonwoven fabric is close to 100% (poor formation), E is approximately 0, and V shows a value that is infinitely large. The smaller the formation index, the better the formation.

[3.13] Molecular weight distribution of 4-methyl-1-pentene polymer (A) Using gel permeation chromatography (GPC) (manufactured by Waters, Alliance 2000 type) with a column manufactured by Tosoh Corporation (GMH type) and o-dichlorobenzene as the mobile phase, the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene were determined, and the molecular weight distribution (Mw/Mn) was calculated.

[3.14] Crystallization temperature and melting point of 4-methyl-1-pentene polymer (A) Using a differential scanning calorimeter (DSC) (PerkinElmer, PYRIS-I type), 5 mg of a sample was heated in an air atmosphere at 300°C for 5 minutes, and then crystallized at a temperature drop rate of 20°C/min to obtain an exothermic curve, the peak temperature of which was the crystallization temperature (Tc). After further cooling to room temperature, the sample was heated to 300°C at a temperature rise rate of 20°C/min to obtain an endothermic curve, and the peak temperature was taken as the melting point (Tm).

The notations in Table 1 are as follows. "SB" indicates the spunbond method. "MB" indicates the meltblown method. "(A)" indicates the 4-methyl-1-pentene polymer (A). "(A1)" indicates the 4-methyl-1-pentene polymer (A1). "(A2)" indicates the 4-methyl-1-pentene polymer (A2). "(B)" indicates the amorphous thermoplastic resin (B). "(B1)" indicates the amorphous thermoplastic resin (B1). "(A)" in the "ΔTg" section indicates the glass transition temperature difference ΔTg of the fiber (A) measured by a differential scanning calorimeter (DSC). "(B)" in the "ΔTg" section indicates the glass transition temperature difference ΔTg of the fiber (B) measured by a differential scanning calorimeter (DSC).

In Comparative Example 1, the glass transition temperature difference ΔTg of the 4-methyl-1-pentene polymer (A) was not 4.0° C. or more. Therefore, the structural strength of the nonwoven fabric of Comparative Example 1 was less than 8 N/50 mm.
In Comparative Example 2, the average fiber diameter of the fibers was not 10 μm or less. In other words, the fibers in Comparative Example 2 were not thin.
These results show that the nonwoven fabrics of Comparative Examples 1 and 2 are not excellent in mechanical strength and heat resistance even though the fibers are thin.

In Examples 1 to 3, the nonwoven fabrics contained fibers containing a 4-methyl-1-pentene polymer (A). The glass transition temperature difference ΔTg of the 4-methyl-1-pentene polymer (A) was 4.0° C. or more. The average fiber diameter of the fibers was 10 μm or less. Therefore, the structural strength of the nonwoven fabrics of Examples 1 to 3 was 8 N/50 mm or more.
As a result, it was found that the nonwoven fabrics of Examples 1 to 3 were excellent in heat resistance and had excellent structural strength even though the fibers were thin.

Claims (15)

The fiber (A) contains a 4-methyl-1-pentene polymer (A),
The glass transition temperature difference ΔTg of the fiber (A) measured by a differential scanning calorimeter (DSC) is 4.0° C. or more,
The nonwoven fabric, wherein the average fiber diameter of the fibers is 10 μm or less. It is a mixed fiber nonwoven fabric,
The fibers further include fibers (B) containing an amorphous thermoplastic resin (B),
The nonwoven fabric according to claim 1, wherein the glass transition temperature difference ΔTg of the fibers (B) measured by a differential scanning calorimeter (DSC) is 0.8° C. or more. The nonwoven fabric according to claim 1 or 2, which has a specific surface area of 1.3 m ² /g or more. The nonwoven fabric according to claim 1 or 2, having a structural strength of 10 N/50 mm or more. The 4-methyl-1-pentene polymer (A) is
90 to 100 mol % of structural units derived from 4-methyl-1-pentene;
0 to 10 mol % of structural units derived from olefins having 2 to 20 carbon atoms other than 4-methyl-1-pentene;
The nonwoven fabric of claim 1 or claim 2, comprising: the amorphous thermoplastic resin (B) contains a cyclic olefin polymer (B-1);
The cyclic olefin polymer (B-1) contains at least one selected from a cyclic olefin copolymer (B-1-1) and a ring-opening polymer of a cyclic olefin (B-1-2),
The nonwoven fabric according to claim 2, wherein the cyclic olefin copolymer (B-1-1) contains the following structural unit (a) and the following structural unit (b):
Structural unit (a): At least one structural unit derived from an olefin compound represented by the following general formula (I).
Structural unit (b): a structural unit derived from a cyclic olefin compound, which is at least one selected from the group consisting of a structural unit represented by the following general formula (II), a structural unit represented by the following general formula (III), and a structural unit represented by the following general formula (IV):

In the above general formula (I), R ³⁰⁰ is a hydrogen atom, or a linear or branched hydrocarbon group having 1 to 29 carbon atoms.

In the general formula (II), u is 0 or 1, v is 0 or a positive integer, and w is 0 or 1. R ⁶¹ to R ⁷⁸ as well as R ^a1 and R ^b1 may be the same or different and each represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms, a cycloalkyl group having 3 to 15 carbon atoms, or an aromatic hydrocarbon group having 6 to 20 carbon atoms. At least two of R ⁷⁵ to R ⁷⁸ may be bonded to each other to form a monocycle or polycycle.

In the general formula (III), x and d are each independently 0 or an integer of 1 or more. y and z are each independently an integer of 0 to 2. R ⁸¹ to R ⁹⁹ may be the same or different and are a hydrogen atom, a halogen atom, an aliphatic hydrocarbon group which is an alkyl group having 1 to 20 carbon atoms or a cycloalkyl group having 3 to 15 carbon atoms, an aromatic hydrocarbon group having 6 to 20 carbon atoms, or an alkoxy group. The carbon atom to which R ⁸⁹ and R ⁹⁰ are bonded may be bonded directly or via an alkylene group having 1 to 3 carbon atoms to the carbon atom to which R ⁹³ is bonded or the carbon atom to which R ⁹¹ is bonded. When y=z=0, R ⁹² and R ⁹⁵ or R ⁹⁵ and R ⁹⁹ may be bonded to each other to form a monocyclic or polycyclic aromatic ring.

In the general formula (IV), R ¹⁰⁰ and R ¹⁰¹ may be the same or different and each represents a hydrogen atom or a hydrocarbon group having 1 to 5 carbon atoms. f is in the range of 1≦f≦18. The nonwoven fabric according to claim 6, wherein the cyclic olefin polymer (B-1) contains the cyclic olefin copolymer (B-1-1). The nonwoven fabric according to claim 7, wherein the cyclic olefin copolymer (B-1-1) contains the structural unit (a) and the following structural unit (c):
Structural unit (c): a structural unit represented by the above general formula (II), in which u is 0 and v is 1. The nonwoven fabric according to claim 2, wherein the glass transition temperature Tg of the fiber (B) is 85°C or higher as measured by a differential scanning calorimeter (DSC). A filter comprising the nonwoven fabric according to claim 1 or 2. The filter of claim 10, wherein the filter is a bag filter. The nonwoven fabric according to claim 1 or 2,
A resin composition including at least one of a thermosetting resin and a thermoplastic resin;
A prepreg comprising: the thermosetting resin has a curing temperature that is 20° C. or more lower than the lowest melting point of the nonwoven fabric;
The prepreg according to claim 12, wherein the thermoplastic resin has a melting point that is 20°C or more lower than the lowest melting point in the nonwoven fabric. A cured or solidified product of the prepreg according to claim 12;
a conductor layer that is disposed on one or both sides of the cured product or the solidified product and that has been subjected to wiring processing;
A printed wiring board comprising: An electronic component having a circuit for transmitting an electrical signal of 1 GHz or more,
An electronic component having an insulating layer comprising a cured or solidified product of the prepreg according to claim 12.