WO2017170791A1

WO2017170791A1 - Heat-resistant fiber structure

Info

Publication number: WO2017170791A1
Application number: PCT/JP2017/013100
Authority: WO
Inventors: 小泉　聡; 純人清岡; 康朗新井田
Original assignee: 株式会社クラレ
Priority date: 2016-03-30
Filing date: 2017-03-29
Publication date: 2017-10-05
Also published as: TW201736659A; TWI787178B; CN108884616A; KR20180123087A; KR102592387B1; JPWO2017170791A1; EP3438338A4; KR20210034122A; US20190055684A1; JP7141334B2; EP3438338A1

Abstract

A heat-resistant fiber structure comprises heat-resistant fibers with a glass transition temperature of at least 100°C and is configured by attaching the heat-resistant fibers to each other.

Description

Heat resistant fiber structure

The present invention relates to a heat-resistant fiber structure that is composed of heat-resistant fibers and is used as a heat insulating material or a sound absorbing material, and a method for manufacturing the same.

Conventionally, fiber materials using heat-resistant fibers have been used as heat insulating materials, sound absorbing materials, etc. in the fields of vehicles, aircraft, architecture, and the like.

In fiber materials such as fiber structures used for these applications, low density is required from the viewpoint of light weight, and strength such as bending stress and tensile strength is also required. Powerfulness at is important. For example, strength at high temperatures is strongly demanded in sound absorbing heat insulating materials incorporated in aircraft wall surfaces and filter applications incorporated in automobile engine parts.

Also, a heat insulating sound absorbing material in which a cotton-like material mixed with a binder is matted has been proposed. More specifically, for example, a high heat-resistant inorganic fiber and a flame-retardant organic fiber having a heat melting temperature or a thermal decomposition temperature of 350 ° C. or higher are uniformly mixed, and the resulting cotton-like material is heat-resistant. A heat-insulating sound-absorbing material is disclosed in which the resin binder is applied and a cotton-like material is heat-treated to form a mat. And it is described by using such a heat insulation sound-absorbing material that a heat insulation sound-absorbing material with high safety can be provided by high heat insulation and sound absorption.

Japanese Patent No. 4951507

However, in the heat insulating sound absorbing material described in Patent Document 1, although it is said that a bendable heat insulating sound absorbing material having high heat insulating properties and sound absorbing properties is obtained, the fibers are bonded to each other with a binder. The strength is not sufficient, and particularly under high temperature conditions, the binder dissolves, and thus there is a problem that the strength decreases.

In addition, in the case of a fiber structure in which fibers are bonded via a binder, it is necessary to increase the amount of the binder in order to increase the strength, but the content of heat-resistant fibers decreases as the binder content increases. There was a problem that heat resistance was not obtained and it was difficult to achieve both strength and heat resistance.

Therefore, the present invention has been made in view of the above-described problems, and an object thereof is to provide a heat-resistant fiber structure having heat resistance and excellent strength such as bending stress and tensile strength.

Means for Solving the Invention

In order to achieve the above object, the heat-resistant fiber structure of the present invention is a fiber structure containing heat-resistant fibers having a glass transition temperature of 100 ° C. or higher, and the heat-resistant fibers are bonded to each other. And

According to the present invention, it is possible to provide a heat resistant fiber structure having heat resistance and excellent strength such as bending stress and tensile strength.

The heat-resistant fiber structure of the present invention (hereinafter simply referred to as “fiber structure”) is composed of a plurality of heat-resistant fibers bonded to each other. And unlike the said conventional fiber structure, the fiber structure of this invention does not use a low-melting-point binder fiber, but has excellent heat resistance and strength by directly bonding heat-resistant fibers to each other. It has the characteristic of providing.

The term “adhesion” as used herein refers to a state in which fibers are softened by heating and the fibers are deformed and meshed by the overlapping force at the intersection, or the fibers are fused and integrated.

<Heat resistant fiber>
As the heat-resistant fiber constituting the fiber structure, a fiber having a glass transition temperature _Tg of 100 ° C. or higher is used.

Here, in general, the glass transition temperature (the temperature at which a polymer starts microscopic molecular motion) is used as an index of heat resistance. A resin having a glass transition point of 100 ° C. or higher is called an engineering plastic. It is preferably used for applications requiring heat resistance. And the fiber using this resin as a raw material is called heat resistant fiber.

This heat-resistant fiber is a fiber that is softened by high-temperature superheated steam (150 ° C. to 600 ° C.) and can be self-adhesive. For example, polyamide fiber, meta-aramid fiber, para-aramid fiber, melamine fiber, polybenzoxazole fiber, Polybenzimidazole fiber, polybenzothiazole fiber, polyarylate fiber, polyethersulfone fiber, liquid crystal polyester fiber, polyimide fiber, polyetherimide fiber, polyetheretherketone fiber, polyetherketone fiber, polyetherketoneketone fiber, polyamideimide A fiber etc. can be mentioned. None of these fibers may be used alone or as a mixture of two or more.

Of these fibers, polyamide fibers are preferably used from the viewpoint of low water absorption and chemical resistance, and polyetherimide fibers are used from the viewpoint of flame retardancy and low smoke generation. preferable.

As the polyamide fiber, for example, a fiber made of a semi-aromatic polyamide which is a polyamide obtained from an aliphatic diamine and a dicarboxylic acid mainly containing an aromatic component is used. The aliphatic diamine is represented by the following general formula (1), preferably n = 4 to 12, more preferably n = 6 and n = 9, and particularly preferably n = 9.

The dicarboxylic acid mainly composed of an aromatic component means that at least 60 mol% or more is an aromatic dicarboxylic acid. Preferred examples include terephthalic acid, isophthalic acid, naphthalenedicarboxylic acid and the like. As an example of a combination of an aliphatic diamine and an aromatic dicarboxylic acid, a combination of an aliphatic diamine (n = 9 in the above general formula (1)) and terephthalic acid is preferable.

Further, as the polyetherimide fiber, an amorphous polyetherimide fiber having no melting point is used, and the glass transition temperature _Tg may be 200 ° C. or higher, even if the fineness is 200 ° C. Those that retain heat resistance under high temperature conditions are preferred. Such heat resistance can be judged from the dry heat shrinkage at 200 ° C., and the amorphous polyetherimide fiber used as the heat resistant fiber of the present invention is dry heat shrinkage at 200 ° C. May be 5.0% or less, and specifically, the dry heat shrinkage is preferably -1.0 to 5.0%.

Further, the amorphous polyetherimide fiber is derived from a polymer and is excellent in flame retardancy. For example, the limiting oxygen index value (LOI value) may be 25 or more, preferably 28 or more, More preferably, it may be 30 or more.

Further, the amorphous polyetherimide fiber may have a single fiber fineness of 15.0 dtex or less. From the viewpoint of production cost and handleability, the single fiber fineness is preferably 0.1 to 12.0 dtex, and more preferably 0.5 to 10.0 dtex.

Further, it is preferable that the amorphous polyetherimide fiber has a fiber strength at room temperature of 2.0 cN / dtex or more. When the fiber strength is less than 2.0 cN / dtex, the process passability when making a fabric such as paper, non-woven fabric, or woven fabric may be deteriorated. More preferably, it is 2.3 to 4.0 cN / dtex, and further preferably 2.5 to 4.0 cN / dtex.

The cross-sectional shape of the heat-resistant fiber (cross-sectional shape perpendicular to the length direction of the fiber) is a general cross-sectional shape such as a round cross-section or an irregular cross-section (flat, elliptical, polygonal, 3-14 leaf shape). , T-shape, H-shape, V-shape, dogbone (I-shape, etc.), and may be a hollow cross-section.

The average fineness of the heat-resistant fiber can be selected, for example, from the range of 0.01 to 100 dtex, preferably 0.1 to 50 dtex, more preferably 0.5 to 30 dtex (particularly 1 to 10 dtex) depending on the application. . When the average fineness is within this range, the balance between the strength of the fiber and the expression of adhesiveness is excellent.

The average fiber length of the heat resistant fiber can be selected, for example, from a range of 10 to 100 mm, preferably 20 to 80 mm, more preferably 25 to 75 mm (especially 35 to 55 mm). When the average fiber length is within this range, the fibers are sufficiently entangled, so that the mechanical strength of the fiber structure is improved.

The crimp rate of the heat resistant fiber is, for example, 1 to 50%, preferably 3 to 40%, more preferably 5 to 30% (particularly 10 to 20%). The number of crimps is, for example, 1 to 100 pieces / inch, preferably 5 to 50 pieces / inch, and more preferably 10 to 30 pieces / inch.

<Fiber structure>
The fiber structure of the present invention includes the above-described heat-resistant fiber and has a structure in which the heat-resistant fibers are bonded to each other, and the shape can be selected according to the use, but is usually a sheet or plate shape. It is.

Further, in the fiber structure of the present invention, in order to have a non-woven fiber structure having a high surface hardness and bending hardness, and having a good balance between lightness and air permeability, a non-woven fiber web is formed. It is necessary that the arrangement state and adhesion state of the fibers to be adjusted are appropriately adjusted. That is, it is desirable that the fibers constituting the fiber web are arranged so as to intersect each other while being arranged substantially parallel to the surface of the fiber web (non-woven fiber).

Furthermore, it is preferable that the fiber structure of the present invention is bonded at the intersection where the fibers intersect. In particular, a fiber structure (molded body) that requires high hardness and strength is a bundle-like adhesive that is bonded in a bundle of several to several tens when fibers other than the intersections are arranged substantially in parallel. Fibers may be formed. A structure in which "scram" is assembled by partially forming a structure in which these fibers are bonded at the intersection of single fibers, the intersection of bundle fibers, or the intersection of single fibers and bundle fibers (Structure in which the fibers are bonded at the intersection and entangled like a mesh, or the structure in which the fibers are bonded at the intersection and constrain the adjacent fibers to each other), and the desired bending behavior, surface hardness, etc. can be expressed. . In the present invention, it is desirable that such a structure be distributed substantially uniformly along the surface direction and the thickness direction of the fiber web.

Here, “arranged substantially parallel to the surface of the fiber web” means that a portion where a large number of fibers are locally arranged along the thickness direction is not repeatedly present. Indicates. More specifically, when an arbitrary cross section of the fiber web of the fiber structure is observed with a microscope, the existence ratio (number of fibers) continuously extending in the thickness direction over 30% of the thickness of the fiber web. The ratio) is 10% or less (particularly 5% or less) with respect to all the fibers in the cross section.

Fibers are arranged in parallel to the fiber web surface because if there are many fibers oriented along the thickness direction (perpendicular to the web surface), the fiber arrangement may be disturbed in the periphery. This is because an unnecessarily large void is generated in the woven fiber, and the bending strength and surface hardness of the fiber structure are reduced. Therefore, it is preferable to reduce this gap as much as possible. For this purpose, it is desirable to arrange the fibers as parallel to the fiber web surface as possible.

In particular, when the fibrous structure of the present invention is a sheet-like or plate-like molded body, when a load is applied in the thickness direction of the fibrous structure, if there is a large void, the void is crushed by the load. As a result, the surface of the molded body is easily deformed. Further, when this load is applied to the entire surface of the molded body, the thickness tends to be reduced as a whole. Therefore, this problem can be avoided if the fiber structure itself is made of a resin filling without voids, but this reduces the air permeability, ensuring that it is difficult to bend when bent (folding resistance) and lightweight. It becomes difficult to do.

On the other hand, in order to reduce the deformation in the thickness direction due to the load, it is conceivable to make the fibers thinner and more densely filled with the fibers, but when trying to ensure lightweight and breathability with only thin fibers , The rigidity of each fiber is lowered, and the bending stress is reduced. In order to ensure bending stress, it is necessary to increase the fiber diameter to some extent. However, if thick fibers are simply mixed, large voids are likely to be formed near the intersections of the thick fibers in the thickness direction. It becomes easy to deform.

Therefore, the fiber structure of the present invention is arranged such that the directions of the fibers are arranged in parallel along the surface direction of the web and dispersed (or the fiber directions are directed in a random direction), so that the fibers intersect each other, and the intersections thereof. By adhering with, a small gap is generated to ensure light weight. Furthermore, since such a fiber structure is continuous, an appropriate air permeability and surface hardness are secured. In particular, when a bundle of fibers bonded in parallel in the fiber length direction is formed in a place where the fibers are aligned in parallel without intersecting with other fibers, it is higher than the case where the fibers are composed of only single fibers. Bending strength can be mainly secured. When a fiber structure having high hardness and strength is desired, several fibers are bonded at the intersection between the intersection points while the fibers are bonded at the intersection where the fibers are crossed. It is preferable to form bundle fibers. Such a structure can be confirmed from the existence state of the single fiber when the cross section of the compact is observed.

In the fiber structure of the present invention, the fiber adhesion rate due to adhesion of heat-resistant fibers is preferably 10 to 85%, more preferably 25 to 75%, and more preferably 40 to 65%. Further preferred.

This may cause inconvenience that the hardness, bending stress, and tensile strength are reduced when the fiber adhesion is less than 10%, and the gap between the fibers becomes smaller when it is greater than 85%. For this reason, there is a case where the apparent density becomes too large and the lightness is impaired. That is, by setting the fiber adhesion rate to 10 to 85%, it becomes possible to further improve the strength such as bending stress and tensile strength without impairing the lightness.

In addition, this fiber adhesion rate can be measured by the method described in the examples described later, and indicates the ratio of the number of cross sections of two or more fibers bonded to the total number of cross sections of the non-woven fiber cross section. Therefore, a low fiber adhesion rate means that the proportion of the plurality of fibers adhering to each other (the proportion of the fibers that are converged and adhered) is small.

In addition, the heat-resistant fibers constituting the non-woven fiber structure are bonded at the contact points of the respective fibers, but in order to develop a large bending stress with as few contacts as possible, this bonding point has a thickness of It is preferable to distribute uniformly along the direction from the surface of the fiber structure to the inside (center portion) and the back surface. When the adhesion points are concentrated on the surface or inside, it is not only difficult to secure a sufficient bending stress, but also the form stability in a portion where the adhesion points are small. Therefore, from the viewpoint of further improving the bending stress without reducing the form stability, in the cross section in the thickness direction of the fiber structure, the central portion of the three regions divided in three in the thickness direction It is preferable that the fiber adhesion rate in the (center portion) is in the above range (10 to 85%).

Further, the uniformity of the fiber adhesion rate in each region (that is, the difference between the maximum value and the minimum value of the fiber adhesion rate) is preferably 20% or less (for example, 0.1 to 20%), preferably 15% or less (for example, 0.5 to 15%), more preferably 10% or less (for example, 1 to 10%).

The fiber structure of the present invention is excellent in hardness, bending strength, folding resistance and toughness because the fiber adhesion rate has such uniformity in the thickness direction.

In the present invention, “region divided into three in the thickness direction” means each region divided into three equal parts by slicing in a direction perpendicular to the thickness direction of the plate-like fiber structure. To do.

As described above, in the fiber structure of the present invention, not only the adhesion by the heat-resistant fiber is uniformly dispersed and the point adhesion is performed, but also the point adhesion of these point adhesion is short (for example, several tens to several hundreds μm). ) In the network structure. With such a structure, the fiber structure of the present invention has a high followability to strain due to the flexibility of the fiber structure even when an external force is applied, and at each adhesion point of finely dispersed fibers. Since the external force is dispersed and reduced, it can be estimated that high bending stress and tensile strength are expressed. On the other hand, the conventional fiber structure in which heat resistant fibers are bonded to each other through binder fibers has a small number of bonding points because the amount of binder fibers is limited to ensure heat resistance, and the binder fibers. Even if the amount of adhesive is increased and the adhesion point is increased, heat resistance cannot be obtained, and furthermore, it is difficult to uniformly disperse the adhesive in the thickness direction of the fiber structure. Can be estimated.

In the fiber structure of the present invention, the existence frequency of single fibers (single fiber end faces) in the cross section in the thickness direction is not particularly limited. For example, the existence frequency of single fibers existing at an arbitrary 1 mm ^{2 of the} cross section may be 100 fibers / mm ² or more (for example, 100 to 300 fibers), but in particular, mechanical characteristics are required rather than light weight. In such a case, the frequency of single fibers is, for example, 100 / mm ² or less, preferably 60 / mm ² or less (for example, 1 to 60 / mm ² ), and more preferably 25 / mm ^2. It may be the following (for example, 3 to 25 pieces / mm ² ). When the presence frequency of the single fiber is too high, the adhesion of the fiber is small, and the strength of the molded body made of the fiber structure is lowered. If the frequency of single fibers exceeds 100 / mm ² , fiber bundle adhesion decreases, making it difficult to ensure high bending strength. Furthermore, in the case of a plate-shaped molded body, it is preferable that the fibers bonded in a bundle shape are thin in the thickness direction of the molded body and have a wide shape in the surface direction (length direction or width direction).

In the present invention, the presence frequency of single fibers is measured as follows. That is, the range corresponding to 1 mm ² selected from the scanning electron microscope (SEM) photograph of the cross section of the compact is observed, and the number of single fiber cross sections is counted. Arbitrary several places (for example, 10 places selected at random) are observed in the same manner, and the average value per unit area of the single fiber end face is defined as the existence frequency of single fibers. At this time, all the number of fibers in a single fiber state are counted in the cross section. That is, in addition to fibers that are completely in a single fiber state, even if fibers are bonded to each other, fibers that are in a single fiber state apart from the bonded portion in the cross section are counted as single fibers.

The heat-resistant fiber in the fiber structure can suppress the loss of the fiber structure due to the loss of the fiber by not connecting the both ends in the thickness direction (the fiber does not penetrate the fiber structure in the thickness direction). . A manufacturing method for arranging the heat-resistant fibers in this way is not particularly limited, but a means for laminating a plurality of fiber molded bodies entangled with the heat-resistant fibers and bonding them with superheated steam is simple and reliable. Moreover, the fiber which connects the both ends of the thickness direction of a fiber structure can be reduced significantly by adjusting the relationship between fiber length and the thickness of a fiber structure. From such a viewpoint, the thickness of the fiber structure is 10% or more (for example, 10 to 1000%), preferably 40% or more (for example, 40 to 800%), more preferably 60% with respect to the fiber length. Or more (for example, 60 to 700%), more preferably 100% or more (for example, 100 to 600%). When the thickness and fiber length of the fiber structure are within such ranges, the mechanical structure such as bending stress of the fiber structure is not lowered, and the loss of the fiber structure due to the fiber dropping or the like can be suppressed.

As described above, the density and mechanical properties of the fiber structure of the present invention are affected by the ratio and the presence state of the bundle-like adhesive fibers. The fiber adhesion rate indicating the degree of adhesion can be easily measured based on the number of bonded fiber cross sections in a predetermined region by taking a photograph of an enlarged cross section of the fiber structure using SEM. However, when the fibers are bonded in a bundle shape, the fibers are bonded in a bundle shape or at an intersection, and therefore, when the density is particularly high, it is difficult to observe as a single fiber.

In the present invention, as an index reflecting the degree of fiber adhesion, the area ratio occupied by the cross section formed by the fiber and the bundle of fiber bundles in the cross section (cross section in the thickness direction) of the fiber structure, that is, the fiber filling rate Can also be used. The fiber filling rate in the cross section in the thickness direction is, for example, 20 to 80%, preferably 20 to 60%, and more preferably 30 to 50%. If the fiber filling rate is too small, there are too many voids in the fiber structure, making it difficult to ensure the desired surface hardness and bending stress. On the other hand, if it is too large, the surface hardness and bending stress can be sufficiently secured, but it becomes very heavy and the air permeability tends to decrease.

The fiber structure of the present invention (particularly, the fiber structure in which fibers are bonded in a bundle and the frequency of single fibers is 100 / mm ² or less) is plate-like (board-like), depending on the load. It is preferable to have a surface hardness that hardly causes deformation such as formation of a concave shape. As such an index, the hardness by an A-type durometer hardness test (a test in accordance with the “hardness test method for vulcanized rubber and thermoplastic rubber” of JIS K6253) is, for example, A50 or more, preferably A60 or more. More preferably, it is A70 or more. If this hardness is too small, it is likely to be deformed by a load applied to the surface.

A fiber structure including such bundle-like adhesive fibers has a low frequency of bundle-like adhesive fibers, and each fiber (bundle) in order to balance bending strength, surface hardness, lightness, and air permeability at a high level. It is preferable that the fibers are bonded at a high frequency at the intersection of the filamentous fibers and / or single fibers). However, if the fiber adhesion rate is too high, the distances between the bonded points are too close to each other, the flexibility is lowered, and it becomes difficult to eliminate distortion due to external stress. For this reason, as described above, the fiber structure of the present invention preferably has a fiber adhesion rate of 85% or less. When the fiber adhesion rate is not too high, a passage by a fine gap can be secured in the fiber structure, and the lightness and air permeability can be improved. Therefore, in order to develop a large bending stress, surface hardness and air permeability with as few contacts as possible, the fiber adhesion rate increases in the thickness direction from the surface of the fiber structure to the inside (center) and back. It is preferable to distribute uniformly along.

In addition, when the adhesion points are concentrated on the surface or inside, it becomes difficult to ensure the air permeability in addition to the bending stress and the shape stability described above. Therefore, in the fiber structure of the present invention, in the cross section in the thickness direction, among the three regions (front surface, central portion, back surface) divided into three in the thickness direction, the fiber adhesion rate in the central portion is in the above-described range. It is preferable that all of the front surface, the central portion, and the back surface are in the above-described range. Further, the difference between the maximum value and the minimum value of the fiber adhesion rate in each region may be 20% or less (for example, 0.1 to 20%), preferably 15% or less (for example, 0.5 to 15). %), More preferably 10% or less (for example, 1 to 10%). In the present invention, if the fiber adhesion rate is uniform in the thickness direction, the bending stress, tensile strength, folding resistance, toughness and the like are excellent. The fiber adhesion rate in this invention is measured by the method as described in the Example mentioned later.

One feature of the fiber structure of the present invention is that it exhibits a bending behavior that cannot be obtained with a conventional fiber structure in which heat-resistant fibers are bonded via binder fibers. In the present invention, in order to express this bending behavior, the bending stress is measured from the repulsive force and bending amount of the sample when the sample is gradually bent according to JIS K7171 “Plastics-Determination of bending characteristics”. Used as an indicator of behavior. That is, the larger the bending stress, the harder the fiber structure, and the more the bending amount (displacement) until the measurement object breaks, the better the bent body.

In the fiber structure of the present invention, the bending stress in at least one direction (preferably all directions) is 0.05 MPa or more (for example, 0.05 to 100 MPa), preferably 0.1 to 30 MPa, more preferably 0. It may be 2 to 10 MPa. If this bending stress is too small, it is easily broken by its own weight or a slight load when used as a board material. Further, if the bending stress is too high, it becomes too hard, and if it is bent beyond the peak of the stress, it is easily broken and broken. In addition, in order to obtain the hardness exceeding 100 MPa, it is necessary to increase the density of the fiber structure, and it is difficult to ensure light weight.

The fiber structure of the present invention can ensure excellent lightness due to voids generated between fibers. Further, unlike the resin foam such as sponge, these voids are continuous rather than independent voids, and thus have air permeability. Such a structure is a structure that is extremely difficult to produce by conventional hardening methods such as a method of impregnating a resin and a method of forming a film-like structure by closely adhering surface portions. .

That is, the fiber structure of the present invention has a low density. Specifically, the apparent density is, for example, 0.03 to 0.7 g / cm ³ , and particularly in applications that require lightweight, 0.05 to 0.5 g / cm ³ , preferably 0.08 to 0.4 g / cm ³ , and more preferably 0.1 to 0.35 g / cm ³ . In applications where hardness is required rather than light weight, the apparent density is, for example, 0.2 to 0.7 g / cm ³ , preferably 0.25 to 0.65 g / cm ³ , more preferably 0.3 to It may be 0.6 g / cm ³ . If the apparent density is too low, it is lightweight, but it is difficult to ensure sufficient bending hardness and surface hardness. Conversely, if it is too high, the hardness can be ensured, but the lightness is reduced. In addition, when the apparent density is lowered, the fibers are entangled and close to a general nonwoven fiber structure bonded at the intersection point, while when the density is increased, the fibers are bonded in a bundle shape and are close to a porous molded body. It becomes.

In addition, "apparent density" said here means the density calculated based on the fabric weight and thickness measured based on the prescription | regulation of JISL1913 (general nonwoven fabric test method).

Basis weight of the fibrous structure of the present invention, for example, can be selected from 50 ~ 10000g / ^{m 2} approximately in the range of preferably 150 ~ 8000g / ^{m 2,} more preferably 300 ~ 6000g / ^{m 2} approximately. In applications where hardness than light weight is required and a basis weight, for example, 1000 ~ 10000g / ^{m 2,} preferably 1500 ~ 8000g / ^{m 2,} further preferably about 2000 ~ 6000g / ^{m 2.} If the basis weight is too small, it is difficult to ensure the hardness, and if the basis weight is too large, the web is too thick and the superheated steam cannot sufficiently enter the web during processing with superheated steam. It becomes difficult to obtain a uniform fiber structure.

When the fiber structure of the present invention is in the form of a plate or sheet, the thickness is not particularly limited, but can be selected from the range of about 1 to 100 mm, for example, 2 to 50 mm, preferably 3 to 20 mm, more preferably Is 5 to 150 mm. If the thickness is too thin, it will be difficult to ensure the hardness, and if it is too thick, the mass will also become heavy, so the handling properties as a sheet will be reduced.

Since the fiber structure of the present invention has a non-woven fiber structure, the air permeability is high. The air permeability of the fiber structure of the present invention is 0.1 cm ³ / cm ² / sec or more (for example, 0.1 to 300 cm ³ / cm ² / sec), preferably 0.5 to ^{3 in} terms of air permeability according to the Frazier method. 250 cm ³ / cm ² / sec (for example, 1 to 250 cm ³ / cm ² / sec), more preferably 5 to 200 cm ³ / cm ² / sec, and usually 1 to 100 cm ³ / cm ² / sec. If the air permeability is too small, it is necessary to apply pressure from the outside in order to allow air to pass through the fiber structure, making it difficult for natural air to enter and exit. On the other hand, if the air permeability is too high, the air permeability increases, but the fiber voids in the fiber structure become too large, and the bending stress decreases.

Since the fiber structure of the present invention has a non-woven fiber structure, it has high heat insulation and low thermal conductivity of 0.1 W / m · K or less, for example, 0.03 to 0.1 W / m. · K, preferably 0.05 to 0.08 W / m · K.

Next, the manufacturing method of the fiber structure of the present invention will be described.

In the method for producing a fiber structure of the present invention, first, the heat-resistant fiber described above is formed into a web. As a method for forming the web, a conventional method, for example, a direct method such as a spunbond method or a meltblowing method, a card method using meltblown fibers or staple fibers, a dry method such as an airlay method, or the like can be used. Among these methods, a card method using melt blown fibers or staple fibers, particularly a card method using staple fibers is widely used. Examples of the web obtained using staple fibers include a random web, a semi-random web, a parallel web, and a cross-wrap web. Of these webs, a semi-random web and a parallel web are preferred when the proportion of bundled adhesive fibers is increased.

In the step of bonding the fibers of the obtained fiber web, the means for bonding the fibers may be a conventional hot air treatment or hot pressing, or the fibers may be bonded by superheated steam. In the case of using superheated steam, the fiber web obtained in the above process is sent to the next process by a belt conveyor and exposed to a superheated steam (high pressure steam) flow, whereby the fiber structure having the nonwoven fiber structure of the present invention. Is obtained. That is, the fiber web conveyed by the belt conveyor passes through the superheated steam flow ejected from the nozzle of the steam spraying device, and the heat-resistant fibers are three-dimensionally bonded to each other by the sprayed superheated steam (thermal bonding). Is done.

By performing the heat treatment with such superheated steam (150 ° C. to 600 ° C.), the heat-resistant fibers can be bonded to each other to obtain a fiber network, so that the inside of the fiber structure in the thickness direction is uniform and It becomes possible to process bulky.

Note that the temperature of the superheated steam sprayed onto the heat resistant fiber is preferably in the range of 150 to 600 ° C. This is because if the temperature is lower than 150 ° C, the energy given to the heat-resistant fibers is insufficient, and the adhesion between the fibers may be insufficient. This is because the uniformity of the fiber adhesion rate may be lowered.

The belt conveyor to be used is not particularly limited as long as it can be processed with superheated steam while compressing the fiber web used for processing to a desired density, and an endless conveyor is preferably used. In addition, it may be a general single belt conveyor, or may be transported by combining two belt conveyors as necessary and sandwiching the web between both belts. By carrying in this way, when the web is processed, it is possible to suppress the inconvenience that the form of the carried web is deformed due to an external force such as superheated steam used for the processing or vibration of the conveyor. It is also possible to control the density and thickness of the treated non-woven fibers by adjusting the distance between the belts.

* When two belt conveyors are combined, a steam injection device for supplying superheated steam to the web is installed in one conveyor and supplies superheated steam to the web through a conveyor net. A suction box may be attached to the opposite conveyor. The suction box can suck and discharge excess superheated steam that has passed through the web. In addition, in order to perform superheated steam treatment on both the front and back sides of the web at the same time, a suction box is installed in the downstream part of the conveyor on the side where the superheated steam injection device is installed, and this suction box is installed. A superheated steam spraying device may be installed in the opposite conveyor. When the front and back of the fiber web are steam-treated when there is no downstream superheated steam injection device and suction box, it can be substituted by reversing the front and back of the fiber web once treated and passing through the treatment device again. .

The endless belt used for the conveyor is not particularly limited as long as it does not interfere with web transport and overheated steam treatment. However, when the superheated steam treatment is performed, the surface shape of the belt may be transferred to the surface of the fiber web depending on the conditions. In particular, in the case of a fiber structure having a flat surface, a fine mesh net is used. The upper limit is 90 mesh, and a fine net having a mesh larger than this has low air permeability and makes it difficult for steam to pass through. The mesh belt is made of metal, heat-treated polyester resin, polyphenylene sulfide resin, polyarylate resin (fully aromatic polyester resin), aromatic polyamide from the viewpoint of heat resistance against superheated steam treatment. A heat resistant resin such as a resin is preferable.

Since the superheated steam injected from the steam injection device is an air stream, unlike the hydroentanglement process or the needle punching process, the superheated steam enters the web without greatly moving the fibers in the web as the object to be processed. It is considered that due to the entry and superheating action of the steam flow into the web, the superheated steam flow effectively covers the surface of each heat-resistant fiber present in the web in a superheated state, thereby enabling uniform thermal bonding. In addition, since this process is performed in a very short time under a high-speed air stream, the heat conduction of the superheated steam to the fiber surface is sufficient, but the process is completed before the heat conduction to the inside of the fiber is sufficiently performed. Therefore, the inconvenience that the whole fiber web to be treated is crushed by the pressure and heat of the superheated steam and the deformation that damages the thickness thereof hardly occur. As a result, thermal bonding is completed so that the degree of bonding in the surface and thickness direction is substantially uniform without causing large deformation in the fiber web.

Furthermore, when obtaining a fiber structure having a high surface hardness and bending strength, when the superheated steam is supplied to the web for processing, the web to be processed is placed between a conveyor belt or rollers with a desired apparent density ( For example, it is important to expose to superheated steam in a compressed state of 0.03 to 0.7 g / cm ³ ). In particular, when a relatively high-density fiber structure is to be obtained, it is necessary to compress the fiber web with sufficient pressure when processing with superheated steam. Furthermore, it is also possible to adjust to a target thickness and density by securing an appropriate clearance between rollers or between conveyors. In the case of a conveyor, since it is difficult to compress the web at a stretch, it is preferable to set the belt tension as high as possible and gradually narrow the clearance from the upstream of the steam treatment point. Furthermore, it is processed into a fiber structure having desired bending hardness, surface hardness, lightness, and air permeability by adjusting the steam pressure and the processing speed.

At this time, if it is desired to increase the hardness, the back side of the endless belt on the opposite side of the nozzle across the web is made of a stainless steel plate or the like so that the steam cannot pass through. Since it reflects here, it adhere | attaches more firmly according to the heat retention effect of vapor | steam. On the other hand, when light adhesion is required, a suction box may be arranged to discharge excess steam to the outside.

The nozzle for injecting superheated steam may be a plate or die in which predetermined orifices are continuously arranged in the width direction, and the orifices may be arranged in the width direction of the web to be supplied. There may be one or more orifice rows, and a plurality of rows may be arranged in parallel. A plurality of nozzle dies having a single orifice array may be installed in parallel.

When using a nozzle with an orifice in the plate, the thickness of the plate may be 0.5 to 1 mm. The orifice diameter and pitch are not particularly limited as long as the target fiber fixation is possible, but the orifice diameter is usually 0.05 to 2 mm, preferably 0.1 to 1 mm, more preferably. 0.2 to 0.5 mm. The pitch of the orifices is usually 0.5 to 3 mm, preferably 1 to 2.5 mm, more preferably 1 to 1.5 mm. If the orifice diameter is too small, the processing accuracy of the nozzle becomes low and the processing becomes difficult, and the operational problem that clogging is likely to occur easily occurs. On the other hand, if it is too large, the steam injection force is reduced. On the other hand, if the pitch is too small, the nozzle holes become too dense and the strength of the nozzle itself is reduced. On the other hand, when the pitch is too large, there is a case where the high-temperature steam does not sufficiently hit the web, so that the web strength is lowered.

The superheated steam is not particularly limited as long as the heat-resistant fiber can be fixed, and may be set depending on the material and form of the fiber used. The pressure is, for example, 0.1 to 2 MPa, preferably 0.2 to 1. 0.5 MPa, more preferably 0.3 to 1 MPa. If the pressure of the steam is too high or too strong, the fibers forming the web may move and cause turbulence, or the fibers may melt too much to partially retain the fiber shape. Also, if the pressure is too weak, it may not be possible to give the web the amount of heat necessary for fiber bonding, or superheated steam may not penetrate the web, and fiber adhesion spots may occur in the thickness direction. It may be difficult to control the uniform jet of steam.

The fiber structure having a non-woven fiber structure obtained in this way has a very high bending stress and surface hardness while having a low density comparable to that of a general nonwoven fabric, and also has air permeability, sound absorption, In addition to heat insulation, it has heat resistance. Therefore, using such performance, it can be applied to applications requiring heat resistance such as automobile interior materials, aircraft inner walls, building material boards, and the like.

Hereinafter, the present invention will be described based on examples. In addition, this invention is not limited to these Examples, These Examples can be changed and changed based on the meaning of this invention, and they are excluded from the scope of the present invention. is not.

Each physical property value in the examples was measured by the following methods. In the examples, “part” means mass part, and “%” means mass%.

Example 1
<Production of fiber structure>
Semi-aromatic polyamide resin consisting of diamine having 9 carbon atoms and terephthalic acid (trade name: GENESTAR, melting point: 265 ° C., glass transition temperature: 125 ° C., thermal decomposition temperature: 400 ° C. ) Was used (fineness: 1.7 dtex, fiber length: 51 mm). Next, by using this heat resistant fiber, a card web having a basis weight of 50 g / m ² was prepared by a card method, and twelve sheets of this web were stacked to obtain a card web having a total basis weight of 600 g / m ² . The card web was transferred to a belt conveyor equipped with a 50 mesh, 500 mm wide stainless steel endless net.

In addition, this belt conveyor consists of a pair of conveyor of a lower conveyor and an upper conveyor, and the vapor | steam injection nozzle is installed in the belt back side of at least one conveyor. Also, superheated steam can be jetted onto the passing web through the belt. Further, a metal roll for adjusting the web thickness (hereinafter sometimes abbreviated as “web thickness adjusting roll”) is provided on each conveyor upstream of the nozzle. The lower conveyor has a flat upper surface (that is, the surface through which the web passes), and one upper conveyor has a lower surface bent along a web thickness adjusting roll. The adjusting roll is arranged to make a pair with the web thickness adjusting roll of the lower conveyor.

Also, the upper conveyor can be moved up and down, so that the web thickness adjusting rolls of the upper conveyor and the lower conveyor can be adjusted to a predetermined interval. Further, the upstream side of the upper conveyor is inclined at an angle of 30 degrees (relative to the lower surface on the downstream side of the upper conveyor) with respect to the downstream portion with respect to the web thickness adjusting roll, and the downstream portion is parallel to the lower conveyor. It is bent so that it may be arranged. When the upper conveyor moves up and down, it moves while maintaining this parallel relationship.

Each of these belt conveyors rotates in the same direction at the same speed, and the two conveyor belts and the web thickness adjusting rolls can be pressurized while maintaining a predetermined clearance. This is for adjusting the web thickness before steaming by operating like a so-called calendar process. That is, the card web fed from the upstream side travels on the lower conveyor, but the interval with the upper conveyor is gradually narrowed before reaching the web thickness adjusting roll. And when this space | interval becomes narrower than the web thickness, the web runs between the upper and lower conveyor belts and is gradually compressed. This web is compressed to a thickness substantially equal to the clearance provided on the web thickness adjusting roll, and is subjected to superheated steam treatment in the thickness state, and thereafter the thickness is maintained at the downstream portion of the conveyor. It is a mechanism to travel. Here, the roll for adjusting the web thickness was adjusted to have a linear pressure of 50 kg / cm.

Next, the steam web is introduced into the steam jetting device provided in the lower conveyor, and steam treatment is performed by ejecting superheated steam at 300 ° C. in the thickness direction of the card web (perpendicularly) from this device. The fiber structure which has the nonwoven fiber structure in a present Example was obtained. In this steam injection device, a nozzle is installed in the lower conveyor so as to blow superheated steam toward the web via a conveyor net, and a suction device is installed on the upper conveyor. Further, another jetting device, which is a combination in which the arrangement of the nozzle and the suction device is reversed, is installed on the downstream side in the web traveling direction of the jetting device, and superheated steam treatment is performed on both the front and back sides of the web. gave.

In addition, the hole diameter of the steam injection nozzle was 0.3 mm, and the steam injection device in which the nozzles were arranged in a line at a 1 mm pitch along the width direction of the conveyor was used. The processing speed was 3 m / min, and the interval (distance) between the upper and lower conveyor belts on the nozzle side and the suction side was 5 mm. The nozzles were arranged on the back side of the conveyor belt so as to be almost in contact with the belt.

<Measurement of basis weight>
Based on JIS L1913, the fabric weight (g / m < ² >) of the produced fiber structure was measured. The results are shown in Table 1.

<Measurement of apparent density>
Based on JIS L1913, the thickness (mm) of the produced fiber structure was measured, and the apparent density (g / cm ³ ) was calculated based on the thickness value and the basis weight value. The results are shown in Table 1.

<Measurement of fiber adhesion rate>
Using a scanning electron microscope (SEM), a photograph in which the cross section of the fiber structure was magnified 100 times was taken. Next, the cross-sectional photograph of the photographed fiber structure in the thickness direction is divided into three equal parts in the thickness direction, and fibers that can be recognized in each of the three divided areas (front side, inside (center part), back side) The ratio of the number of cut surfaces in which the fibers are bonded to the number of cut surfaces (fiber end surfaces) was determined.

More specifically, the ratio of the number of cross-sections in a state where two or more fibers are bonded out of the total number of cross-sections of fibers that can be recognized in each region is expressed as a percentage based on the following formula (1).

In addition, in the part which fibers contact, there is a part which is simply contacting without bonding, and a part which is bonded by bonding, but by cutting the fiber structure for microscopic photography, the fiber In the cut surface of the structure, the fibers that are simply in contact with each other were separated by the stress of each fiber. Therefore, in the cross-sectional photograph, the contacting fibers are assumed to be bonded.

Also, for each photograph, all the fibers whose cross section could be confirmed were counted, and when the number of fiber cross sections was 100 or less, a photograph to be observed was added so that the total cross section of the fibers exceeded 100. Moreover, the fiber adhesion rate was calculated | required about each area | region divided into three equally, and the difference (namely, uniformity) of the maximum value and minimum value was also calculated | required together. The results are shown in Table 1.

<Measurement of bending stress>
In accordance with the provisions of JIS K7171 (Plastics-Determination of bending characteristics), a test piece (width: 10 mm, length: 100 mm) is prepared from the produced fiber structure, the distance between supporting points is 80 mm, and the test speed is 10 mm. Bending stress (MPa) was measured as / min. The results are shown in Table 1.

<Measurement of tensile strength>
In accordance with the provisions of JIS L1913 (general non-woven fabric test method), a test piece (width 30 mm, length 150 mm) is prepared from the produced fiber structure, the grip interval is 100 mm, and the test speed is 10 mm / min. Tensile strength (N / 30 mm) was measured. The results are shown in Table 1.

(Example 2)
<Production of fiber structure>
As heat-resistant fiber, amorphous polyetherimide fiber (manufactured by Kuraray Co., Ltd., trade name: KURAKIISSS, glass transition temperature: 215 ° C., thermal decomposition temperature: 540 ° C., fineness: 8.9 dtex, fiber length 51 mm) Got ready. Next, using this heat resistant fiber, a card web having a basis weight of 100 g / m ² was prepared by a card method, and formed into a sheet using a hydroentanglement method.

Next, after laminating 10 sheets of this sheet, the laminated body was transferred to a belt conveyor equipped with a 50 mesh, 500 mm wide stainless steel endless net.

Next, in the same manner as in the first embodiment, the curd web is introduced into the steam injection device provided in the lower conveyor, and superheated steam at 330 ° C. is passed from the device toward the thickness direction of the card web. (Perpendicularly) and steam treatment was performed to obtain a fiber structure having a nonwoven fiber structure in this example.

Next, in the same manner as in Example 1 described above, basis weight measurement, apparent density measurement, fiber adhesion rate measurement, bending stress measurement, bending load measurement, and tensile strength measurement were performed. The results are shown in Table 1.

(Example 3)
<Production of fiber structure>
Nine card webs used in Example 1 were laminated and subjected to a hot press treatment at 260 ° C. for 1 minute using a hot press apparatus to obtain a fiber structure.

(Comparative Example 1)
<Production of fiber structure>
Semi-aromatic polyamide fiber prepared in Example 1 and polypropylene / polyethylene core-sheath composite fiber (manufactured by Ube Eximo Co., Ltd., HR-NTW as a binder fiber, glass transition temperature of the core: −20 ° C., sheath Glass transition temperature: −120 ° C., core thermal decomposition temperature: 240 ° C., sheath thermal decomposition temperature: 270 ° C., fineness: 1.7 dtex, fiber length: 51 mm), and a mass ratio of 80/20 Mixed cotton. Next, a card web having a basis weight of 50 g / m ² was prepared by using the mixed cotton fiber by a card method, and six sheets of this web were stacked to obtain a card web having a total basis weight of 300 g / m ² . And the fiber structure of this comparative example was obtained by heat-processing this card | curd web for 1 minute at 150 degreeC with a hot air dryer.

As shown in Table 1, the fiber structures of Examples 1 to 3 in which heat-resistant fibers having a glass transition temperature of 100 ° C. or higher are thermally bonded to each other are compared in which the heat-resistant fibers are bonded to each other through a binder. It is superior to the fiber structure of Example 1 in bending stress and tensile strength. In particular, in the fiber structures of Examples 1 and 2 with high uniformity of fiber adhesion, the values of bending stress and tensile strength are significantly higher than those of Comparative Example 1, and the strength is very excellent. I can say that.

In addition, in the fiber structures of Examples 1 and 2, compared with Comparative Example 1, the maintenance ratio of tensile strength (tensile strength at 180 ° C./tensile strength at normal temperature) is very large, and heat resistance is extremely high. It can be said that it is excellent.

In addition, as shown in Table 1, the bending stress of the fiber structure of Comparative Example 1 is 0, but such a fiber structure is soft enough to bend by its own weight, and the bending stress is below the measurement limit, For example, even when it is constructed as a heat insulating material, it is inferior in handleability because it hangs down without being along a wall surface or a ceiling surface. On the other hand, the bending stress of Example 3 is 0.4 MPa, which is superior to that of Comparative Example 1. If the bending stress is about 0.4 MPa, construction can be performed without sagging from the wall surface. It can be said that it is greatly improved from the viewpoint of.

Moreover, in the fiber structure of Example 3, compared with Comparative Example 1, it can be said that the maintenance ratio of tensile strength (tensile strength at 180 ° C./tensile strength at normal temperature) is large and excellent in heat resistance. .

On the other hand, in Comparative Example 1, since the fibers are bonded to each other with a binder, the fiber adhesion rate is remarkably reduced as shown in Table 1. As a result, the bending stress and It can be said that the tensile strength is extremely low.

As described above, the present invention is composed of heat resistant fibers and is suitable for heat resistant fiber structures used as heat insulating materials and sound absorbing materials.

Claims

A heat-resistant fiber structure comprising heat-resistant fibers having a glass transition temperature of 100 ° C. or higher, wherein the heat-resistant fibers are bonded to each other.
The heat-resistant fiber structure according to claim 1, wherein the heat-resistant fiber has a fiber adhesion rate of 10 to 85%.
The heat resistance according to claim 1 or 2, wherein, in a cross section in the thickness direction of the fiber structure, a fiber adhesion rate in a central portion is 10 to 85% among three regions equally divided in the thickness direction. Fiber structure.
The heat-resistant fiber structure according to claim 2 or 3, wherein the uniformity of the fiber adhesion rate is 20% or less.
The heat resistant fiber structure according to any one of claims 1 to 4, wherein the apparent density is 0.03 to 0.7 g / cm 3 .