JPH11117163A - Heat resistant nonwoven fabric and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonwoven fabric excellent in mechanical properties, dimension stability and heat resistance. SOLUTION: This nonwoven fabric having 0.1-0.7 g/cm<3> bulk density and 1.0-1.5 ratio (MD/CD) of tensile strength in the machine direction(MD) to that in the cross direction(CD) is obtained by mixing aromatic polyamide fibers with binder fibers comprising core and sheath type conjugated staple fibers to form a nonwoven web, laminating the obtained nonwoven web by arranging the nonwoven web in the proportion of 40-50 wt.% of the weight of the nonwoven fabric as an intermediate layer so that the orientation of the fibers may cross to the machine direction, and the nonwoven webs of each 30-25 wt.% thereof on the front and back faces of the intermediate layer so that the orientation of the fibers may be in the machine direction to provide a laminated nonwoven web, interlacing the laminated nonwoven web by a high pressure fluid flow, and wholly or partially subjecting the interlaced laminated nonwoven web to a thermo-compression bonding treatment.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant non-woven fabric, and more particularly to a resin-impregnated light-weight composite material such as a honeycomb material for printed circuit boards and a cleaning material for a copying machine. It can be used taking advantage of the balance with the characteristics.

[0002]

2. Description of the Related Art Conventionally, aromatic polyamide fibers and aromatic polysulfide fibers have been used as heat-resistant nonwoven fabrics.
Nonwoven fabrics obtained by a wet papermaking method, a thermocompression bonding method, a mechanical entanglement method, and the like are included.

As a nonwoven fabric using an aromatic polyamide fiber, a nonwoven fabric formed by mixing an aromatic polyamide fiber and pulp-like particles having the same composition by a wet paper-making method is disclosed in
No. 15, non-woven fabric formed by thermocompression bonding using undrawn aromatic polyamide fibers as an adhesive element, and aromatic polyamide fibers and undrawn fibers disclosed in Japanese Patent Publication No. 2-40779. A nonwoven fabric is known, in which a nonwoven web made of fibers is entangled by the action of a water stream, and then the fibers are fused together by thermocompression bonding.

As nonwoven fabrics using aromatic polysulfide fibers, there are known a nonwoven fabric in which constituent fibers are mechanically entangled with each other by needle punching, and a nonwoven fabric by a spun bond method disclosed in Japanese Patent Publication No. 57-16954. Have been.

[0005] However, the above-mentioned nonwoven fabric obtained by a wet method using aromatic polyamide fibers is useful because of its excellent heat resistance. However, since the nonwoven fabric is calendered under high temperature and high pressure, it is inevitably formed into paper-like resin. Low impregnation,
There is a problem that the sheet lacks flexibility and drape. Further, when trying to create a thick sheet, it is difficult to make the processing uniform in the sheet thickness direction during calendering, and there is a problem of generation of microvoids, and there are drawbacks that the use and the sheet form are limited. .

A nonwoven fabric obtained by thermocompression bonding using an undrawn aromatic polyamide fiber as an adhesive element requires high-temperature welding of 300 ° C. or more and high linear pressure of over 100 kg / cm to obtain sufficient nonwoven fabric strength. Therefore, it is difficult to apply a normal calendar or the like.

The hydroentangled nonwoven fabric made of aromatic polyamide fiber has good heat resistance and excellent strength,
Although the fibers are mechanically entangled with each other, there is no bonding by bonding between the fibers. Further, regarding a method for producing a nonwoven fabric in which an aromatic polyamide fiber and an undrawn fiber are entangled by the action of a water stream and then the fibers are fused by thermocompression bonding, the storage stability of the fiber in the process of producing the undrawn fiber is described. In addition, there are problems such as lack of crimping, crimping of the crimp is less than that of the ordinary drawn fiber, and lack of stability at the time of storage of the fiber due to adhesion or the like.

In the method in which the aromatic polysulfide fiber is subjected to needle punching to form a nonwoven fabric, a nonwoven fabric having a low basis weight is difficult to obtain because a certain weight per unit area is required to maintain the strength of the nonwoven fabric. Manufacturing is difficult. In addition, the nonwoven fabric formed by the spunbond method is restricted in local movement due to long fibers, and usually has a strong difference between the machine direction and the transverse direction.

[0009]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems and provides a heat-resistant nonwoven fabric having no spots and excellent in mechanical properties, dimensional stability and heat resistance, and a method for producing the same. .

[0010]

The present invention attains the above object and has the following constitution.

That is, the present invention comprises a core-sheath composite short fiber having a softening point of a main fiber having a decomposition point of 300 ° C. or more and a sheath component of 180 ° C. or more and a melting point difference between the sheath component and the core component of 30 ° C. or more. Binder fibers are entangled by high-pressure liquid flow treatment, and the intersection between the fibers constituting the web is a non-woven fabric that is entirely or partially thermally fused by thermocompression bonding,
Consisting of layers 1 to 5 satisfying the following conditions, the arrangement of the constituent fibers in each layer is continuously changing between the layers,
The bulk density is 0.1 to 0.7 g / cm ³ , and the ratio (M) of tensile strength between the machine direction (MD) and the cross direction (CD) of the nonwoven fabric
D / CD) is 1.0 to 1.5, and the shrinkage ratio of the nonwoven fabric after leaving in a constant temperature air at 150 ° C. for 2 hours is in the machine direction;
The gist of the present invention is a heat-resistant nonwoven fabric characterized by being 3% or less in both the lateral direction. Layer 1: The arrangement of the constituent fibers is mainly in the machine direction. Layer 2: The arrangement of the constituent fibers in the machine direction and the arrangement in the transverse direction are mixed. Layer 3: The arrangement of the constituent fibers is mainly in the horizontal direction. Layer 4: The arrangement of the constituent fibers in the machine direction and the arrangement in the transverse direction are mixed. Layer 5: The arrangement of the constituent fibers is mainly in the machine direction.

A main fiber having a decomposition point of 300 ° C. or more is mixed with a binder fiber comprising a core-sheath composite short fiber having a softening point of 180 ° C. or more and a melting point difference between the sheath component and the core component of 30 ° C. or more. A nonwoven web is formed on the intermediate layer, and a nonwoven web having a basis weight of the nonwoven fabric of 40 to 50% by weight is placed on the intermediate layer so that the fiber arrangement is perpendicular to the machine direction. The laminated nonwoven web in which the fiber arrangement is in the machine direction is entangled by a high-pressure liquid flow, and then the sheath component of the binder fiber is (softening point −10 ° C.) to (softening). (+ 50 ° C. point), heat-welding treatment is performed and the whole or part is heat-sealed, the bulk density of the nonwoven fabric is 0.1 to 0.7 g / cm ³ , and the machine direction (MD) of the nonwoven fabric is Ratio of tensile strength to transverse direction (CD) (MD / CD) It is an gist a method for manufacturing a heat-resistant nonwoven fabric, characterized by 1.0 to 1.5.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
In the present invention, a main fiber having a decomposition point of 300 ° C. or higher is used. When the decomposition point is lower than 300 ° C., the heat-resistant nonwoven fabric aimed at by the present invention cannot be obtained, which is not preferable. As a fiber whose decomposition point is 300 ° C or higher,
Aromatic polyamide fiber, polyphenylene sulfide fiber and the like can be mentioned. In the present invention, aromatic polyamide fibers are preferably used. In the aromatic polyamide fiber, the main repeating unit of the polymer is metaphenylene isophthalamide (hereinafter referred to as meta-aramid) in which the coordination relationship between an amide bond and a phenylene group is in the meta position or para-coordination relationship in para-coordination. And short fibers made of wholly aromatic polyamide which is paraphenylene terephthalamide (hereinafter referred to as para-aramid). The aromatic polyamide short fiber may be a meta-aramid or a para-aramid alone, but in order to obtain a nonwoven fabric having both heat resistance and mechanical properties, a mixed system of both is more preferable. At that time, the ratio (weight ratio) of meta-aramid / para-aramid is preferably in the range of 1/2 to 2/1.

The average fineness of the main fiber is preferably 1 to 10 denier, and the average fiber length is preferably 10 to 80 mm. Exceeding these ranges is not preferable because the card passing property in a normal card machine is deteriorated, or web unevenness tends to occur.

In the core / sheath composite type binder fiber used in the present invention, the softening point of the sheath component as the binder component is 180 ° C.
That is all. Preferably, a polymer having a softening point of 180 to 200 ° C is used. If the softening point is lower than 180 ° C., the sheath component is melted when the nonwoven fabric of the present invention is exposed to a high temperature and does not function as a binder, so that the object of the present invention cannot be obtained. On the other hand, when the temperature exceeds 200 ° C., the temperature of the flat roll or the concave and convex roll used in forming the nonwoven fabric needs to be high, which is not preferable.

The melting point difference between the sheath component and the core component is 30 ° C.
Above. When the difference in melting point is less than 30 ° C., the stability of the heat-sealing treatment is deteriorated during the formation of the nonwoven fabric, and the core component is affected by the heat treatment, and the strength as a fiber cannot be maintained. Is undesirably reduced.

In the present invention, a core-sheath composite type binder fiber containing a copolyester as a sheath component and polyethylene terephthalate as a core component is preferably used. Polyethylene terephthalate to be disposed in the core component may be a homopolymer, or isophthalic acid, phthalic acid, adipic acid, sebacic acid, 1,4-butanediol, diethylene glycol, triethylene glycol as long as the object of the present invention is not impaired. And the like may be copolymerized by about 10 mol%, and additives such as a matting agent and a lubricant may be added. Examples of the copolymerized polyester to be disposed in the sheath component include a polyester obtained by copolymerizing polyethylene terephthalate with isophthalic acid, and a polyester obtained by copolymerizing polyethylene terephthalate with 1,4-butanediol and ε-caprolactone.

The average fineness of the binder fiber used in the present invention is preferably 1 to 10 denier, and the fiber length is preferably 10 to 80 mm. More preferably, the fineness is in the range of 2 to 5 denier and the fiber length is in the range of 20 to 60 mm. If the fineness is less than 1 denier, the number of binder fibers constituting the nonwoven fabric increases, and the texture of the nonwoven fabric subjected to the heat bonding treatment becomes hard, which is not preferable. On the other hand, if it exceeds 10 denier, the fiber diameter becomes large, the smoothness of the surface of the nonwoven fabric is impaired, and the number of binder fibers becomes thin, which is not preferred because the strength of the nonwoven fabric is reduced.

The heat-resistant nonwoven fabric according to the present invention comprises
It is preferable that it is composed of 80% by weight and 60 to 20% by weight of binder fibers. When the main fiber is less than 40% by weight,
Although the tensile strength of the nonwoven fabric is increased due to the high proportion of the binder fiber, the nonwoven fabric tends to shrink when used in a high temperature, and tends to have poor heat resistance and dimensional stability. On the other hand, if the main fiber exceeds 80% by weight, the heat resistance of the non-woven fabric is excellent, but the tensile strength of the non-woven fabric is reduced due to the small proportion of the binder fiber. Tends to occur.

The basis weight of the heat-resistant nonwoven fabric of the present invention is 40 to 1
It is preferably in the range of 50 g / m ² , more preferably 60 to 120 g / m ² . The basis weight is 40 g / m ²
If it is less than the above, the basis weight of the stacked parallel card webs is small, and it is difficult to prepare. On the other hand, when it exceeds 150 g / m ² , the constituent fibers are not sufficiently entangled three-dimensionally when the non-woven web is subjected to the entanglement treatment by the high-pressure liquid flow, and thus the whole is not sufficiently integrated, which is not preferable.

The heat-resistant nonwoven fabric of the present invention is composed of layers 1 to 5 satisfying the following conditions. The arrangement of the constituent fibers in each layer is continuously changed between the layers, and is different from the machine direction (MD) of the nonwoven fabric. The ratio of tensile strength to the direction (CD) (MD /
CD) is 1.0 to 1.5. Layer 1: The arrangement of the constituent fibers is mainly in the machine direction. Layer 2: The arrangement of the constituent fibers in the machine direction and the arrangement in the transverse direction are mixed. Layer 3: The arrangement of the constituent fibers is mainly in the horizontal direction. Layer 4: The arrangement of the constituent fibers in the machine direction and the arrangement in the transverse direction are mixed. Layer 5: The arrangement of the constituent fibers is mainly in the machine direction.

When the tensile strength ratio (MD / CD) of the nonwoven fabric is outside the above range, that is, when the strength in the transverse direction is higher than the strength in the machine direction, or when the arrangement of the constituent fibers of the nonwoven fabric has a large directionality. In addition, the dimensional change rate due to heat or moisture absorption differs in the machine direction and the lateral direction. For example, when used for a circuit board or the like, the substrate has poor mechanical properties and dimensional change rate, which is not preferable.

The heat-resistant nonwoven fabric of the present invention can be efficiently produced by the following method. That is, a nonwoven web is formed by mixing the main fiber and the binder fiber composed of the core-sheath composite short fiber, and the nonwoven web having a basis weight of the nonwoven fabric of 40 to 50% by weight is arranged in the intermediate layer in the machine direction. And a nonwoven web having a basis weight of the nonwoven fabric of 30 to 25% by weight, each of which is laminated so that the fiber arrangement is in the machine direction. And then heat-welded at a temperature in the range of (softening point −10 ° C.) to (softening point + 50 ° C.) of the sheath component of the binder fiber to thermally or completely fuse the heat-resistant nonwoven fabric. .

First, 40 to 80% by weight of main fibers (preferably aromatic polyamide short fibers) and binder fibers 6
From 0 to 20% by weight is carded by a parallel card machine to prepare a parallel web in which the fiber arrangement direction is one direction. A nonwoven web having a basis weight of a heat-resistant nonwoven fabric of 40 to 50% by weight was used as an intermediate layer, and the fiber arrangement thereof was perpendicular to the machine direction.
A nonwoven web of 0 to 25% by weight is laminated so that the fiber arrangement is in the machine direction.

Since the fibers constituting the nonwoven fabric have respective directions in the machine direction and the direction perpendicular to the machine direction, the tensile strength in the machine direction (MD) and the transverse direction (C
D) the tensile strength ratio (MD / CD) in a specific range,
In addition, the shrinkage in the machine direction / lateral direction of the nonwoven fabric that has been left in a high temperature is regulated, and the nonwoven fabric has excellent dimensional stability. In general, short-fiber nonwoven fabrics made of nonwoven webs obtained by a parallel card machine have different mechanical performances / shrinkage ratios in the machine direction / lateral direction because the fibers are arranged in one direction. The nonwoven fabric of the present invention, by arranging fibers in each direction of the machine direction and the direction orthogonal to the machine direction,
The nonwoven fabric has excellent mechanical performance and heat shrinkage resistance in any direction.

If the basis weight of the nonwoven webs disposed in the intermediate layer and the upper and lower layers is out of the above range, the mechanical properties of the produced nonwoven fabric, particularly, the tensile strength in the machine direction (MD) and the transverse direction (CD) ) Is between 1.0 and 1.0 (MD / CD).
1.5, the large anisotropy occurs in the fiber direction of the non-woven fabric, the object of the present invention is not obtained, and, for example, when used for a resin impregnated laminate for a circuit board, This is inconvenient because of lack of dimensional stability.

By arranging the fiber arrangement of the nonwoven webs arranged in the upper and lower layers so as to be in the machine direction, when the constituent fibers are entangled by the high-pressure liquid flow, the fibers are not disturbed by the accompanying airflow, and A good nonwoven fabric without spots can be obtained. In addition, the fiber arrangement of the nonwoven web to be arranged in the intermediate layer is arranged so as to be in the direction perpendicular to the machine direction, and when the constituent fibers are entangled by the high-pressure liquid flow, the movement of the web of the intermediate layer is suppressed by the upper and lower layers. The fibers can be entangled with each other to improve the lateral strength of the nonwoven fabric.

In the present invention, as a means for performing three-dimensional entanglement, a spunlace method in which fibers are entangled by a high-pressure liquid flow is applied. By applying the spunlace method, it is possible to produce a three-dimensionally entangled nonwoven fabric in which the main fibers and the binder fibers constituting the nonwoven web are densely integrated with each other. Here, three-dimensional confounding is
The structure in which the main fiber and the binder fiber forming the nonwoven web are entangled with each other, and entangled not only in the vertical and horizontal directions of the nonwoven fabric, but also in the thickness direction of the nonwoven fabric, to form an integrated structure. It means having.

Next, a spunlace method is applied to the nonwoven web,
That is, a method of performing the high-pressure liquid flow treatment will be described.
The confounding treatment in the present invention means that the pore size is, for example, 0.05 to
A device in which a plurality of injection holes of 2.0 mm, preferably 0.1 to 0.4 mm are arranged in one row or a plurality of rows at an injection hole interval of 0.3 to 10 mm, and the injection pressure is 5 to 150 kg /
A method of injecting a high-pressure liquid of cm ² from an injection hole is employed. The arrangement of the injection holes is arranged in a row in a direction orthogonal to the traveling direction of the support plate and the laminated nonwoven web placed thereon. Generally, water or hot water is used as the high-pressure liquid. The distance between the injection hole and the laminated nonwoven web is 1 to
It is good to be 15 cm. If this distance is less than 1 cm, the formation of the heat-resistant nonwoven fabric obtained by this treatment tends to be disordered, while if this distance exceeds 15 cm, the impact force when the liquid stream collides with the laminated nonwoven web layer decreases. Therefore, three-dimensional confounding is not sufficiently performed, which is not preferable.

When a high-pressure liquid flow is applied to the laminated nonwoven web, a pressure of 40 k
Pre-entanglement is performed with a high-pressure liquid flow of g / cm ² or less. If the pressure of this first high-pressure liquid flow is 40 kg / cm ² or more, the fibers in the surface layer of the nonwoven web are disturbed by the accompanying airflow generated by the high-pressure liquid flow, which causes the occurrence of spots and is undesirable. . Subsequently, as a second entanglement treatment, by entanglement with a high-pressure liquid flow having a pressure of 40 kg / cm ² or more, the constituent fibers of the intermediate layer and the upper and lower layers of the laminated nonwoven web are densely entangled and integrated. At the same time, the constituent fibers of the upper layer and the constituent fibers of the lower layer are entangled.

Further, the nonwoven web is further inverted,
By performing entanglement with a high-pressure liquid flow, a nonwoven fabric that is densely integrated on both sides can be obtained.

The porous support plate used in the present invention is made of metal or polyester as long as the high-pressure liquid flow can pass through the support plate and the laminated nonwoven web placed thereon. Either may be used. The configuration of the mesh of the porous support plate may be appropriately selected depending on the use of the nonwoven fabric, but a mesh in the range of 10 to 150/25 mm is preferably used. When the mesh size is less than 10/25 mm, the nonwoven fabric has a perforated state with clear openings, and tends to lack dimensional stability. On the other hand, 15
If it exceeds 0/25 mm, the amount of energy required for the high-pressure liquid flow to pass through the laminated nonwoven web becomes large.

The densely integrated nonwoven fabric obtained by the above method is subjected to a drying treatment after removing excess moisture using a known moisture removing device, such as a mangle.

Next, the dried non-woven fabric is introduced into a hot-pressing apparatus, and the softening point of the sheath component of the binder fiber (−10 ° C.)
(Softening point + 50 ° C.) Heat-welding treatment is performed in the temperature range and the whole or part is heat-sealed to reduce the bulk density of the nonwoven fabric to 0.1.
1 to 0.7 g / cm ³ . 0.7 g / cm bulk density
^If it exceeds ³ , it is less preferable than the purpose and application of the present invention.
For example, when used as a resin sheet for a printed circuit, when a heat-resistant nonwoven fabric is impregnated with a resin, it is difficult to impregnate the resin into the inside of the nonwoven fabric, which is inconvenient. 0.1 g / cm
^{If it is} smaller than ³ , the form stability of the nonwoven fabric is poor, and the mechanical strength is poor.

As the thermal pressing device used in the present invention, it is preferable to perform the thermal pressing with a flat roll or an uneven roll. The adjustment of the bulk density is obtained by changing the linear pressure between the rolls and adjusting the gap between the rolls.

The surface temperature of the roll is set to a temperature of (softening point−10 ° C.) to (softening point + 50 ° C.) of the sheath component of the binder fiber. When the temperature is less than (softening point -10 ° C), the effect of the heat-pressure bonding treatment is poor, and the sheath component does not melt sufficiently and is not sufficiently bonded at the intersection of the fibers, so that the mechanical strength of the obtained nonwoven fabric is low. Not preferred. On the other hand, if the temperature exceeds (softening point + 50 ° C.), the effect of the heat-pressure bonding treatment becomes too large, so that the fusion point between the main fiber and the binder fiber tends to be excessively crystallized or thermally deteriorated, and the texture is impaired. Not only that, the bonding points become brittle and the strength and flexibility of the nonwoven fabric are lost, which is not preferable.

The linear pressure between the rolls at the time of performing the hot pressing process is as follows:
When using a flat roll, the range is preferably 30 to 100 kg / cm, and when using a concavo-convex roll, it is preferably within a range of 5 to 50 kg / cm. . Below the lower limit of the above range (less than 30 kg / cm for a flat roll, less than 5 kg / cm for a concavo-convex roll), the effect of the heat-welding treatment is poor, and a nonwoven fabric having the bulk density desired by the present invention cannot be obtained. On the other hand, if it exceeds the upper limit of the above range (in the case of a flat roll, it exceeds 100 kg / cm, and in the case of a concavo-convex roll, it exceeds 50 kg / cm), a nonwoven fabric having a bulk density intended for the present invention can be obtained. This is not preferred because the texture becomes firm.

When performing the heat-pressing treatment using the concave-convex roll, the heat-pressing area does not necessarily have to be a circular shape, but has an area of 0.1 to 1.0 mm ² and a press-contact density of 5 to 1.0. 100 points / cm ² , preferably 10 to 8
0 point / cm ² , and the ratio of the area of the entire heat-pressed area to the total surface area of the nonwoven fabric, that is, the press-contact area ratio is 5 to 50%, preferably 8 to 40%.

The heat-resistant nonwoven fabric of the present invention has a shrinkage ratio in the machine direction / lateral direction of not more than 3% when subjected to heat treatment at 150 ° C. for 2 hours using an air oven type heat treatment machine.
That is, five sample pieces of 20 cm long × 20 cm wide are prepared, and 15 pieces are prepared for each sample using an air oven type heat treatment machine.
After leaving for 2 hours in an atmosphere of 0 ° C., the length / width of the sample is measured, and a nonwoven fabric having an average value of 3% or less is defined as a heat-resistant nonwoven fabric in the present invention.

The nonwoven fabric of the present invention having a shrinkage ratio of 3% or less in the machine direction / horizontal direction in a heat treatment for 2 hours in an atmosphere of 150 ° C., for example, exhibits a shrinkage upon continuous use of recent high-speed printing equipment. It is used well without generation.

In the case of the nonwoven fabric having an average value of more than 3%, not only the binder fiber cannot withstand the above-mentioned atmosphere and shrinkage occurs, but also, in some cases, the sheath component is melted and the shape of the nonwoven fabric is spoiled. In addition, the use at high temperatures results in an unsuitable nonwoven fabric, which is not the object of the present invention, and is therefore not preferred.

[0042]

Next, the present invention will be specifically described based on examples, but the present invention is not limited to these examples. In the examples, the measurement of each characteristic value was performed by the following method.

(1) Softening point (° C.): The penetration temperature into a polymer in a silicon bath was measured using an automatic melting point measuring apparatus, AMP-I type, manufactured by Yanagi Head Office.

(2) Weight of nonwoven fabric (g / m ² ): Five sample pieces each having a sample width of 10 cm and a sample length of 10 cm were prepared, the weight thereof was measured, and the average value was regarded as the weight (g / m ² ). .

(3) Tensile strength of nonwoven fabric (kg / 5cm
Width): Ten sample pieces each having a sample width of 5 cm and a sample length of 15 cm were prepared, and each sample piece was gripped with Toyo Baldwin's Tensilon UTM-4-1-100 at an interval of 10 c.
m, the maximum tensile strength was individually measured under the conditions of a tensile speed of 10 cm / min, and the average value (kg / 5 cm width) was taken as the tensile strength of the nonwoven fabric.

(4) Tensile elongation (%) of nonwoven fabric: The average value (%) of the elongation showing the maximum tensile strength at the time of measuring the tensile strength was defined as the tensile elongation of the nonwoven fabric.

(5) Bulk density of nonwoven fabric (g / cm ³ ): Five sample pieces having a sample width of 10 cm and a sample length of 10 cm were prepared.
4.5 using a thickness measuring device manufactured by Daiei Kagaku Seiki Seisakusho Co., Ltd.
g / cm ² , the thickness (m
m) was measured, the average value was defined as the thickness (mm), and the thickness was determined by the following equation. Bulk density (g / cm ³ ) = (basis weight) / (thickness) / 1000 (6) Shrinkage (%): Five specimens of 20 cm long × 20 cm wide were prepared, and each of them was treated with an air oven type heat treatment machine. After each sample was allowed to stand at 150 ° C. in an atmosphere temperature for 2 hours, the length / width of the sample was measured, the respective shrinkage ratios were measured, and the average value was defined as the shrinkage ratio (%). Here, it is assumed that the nonwoven fabric having a shrinkage of 3% or less has good dimensional stability at high temperatures.

Example 1 As the aromatic polyamide fiber, para-aramid fiber A (manufactured by Nippon Aramid Co., trade name: Twaron R) having an average fineness of 1.9 denier and an average fiber length of 50 mm, and an average fineness of 2.
0 denier, meta-aramid fiber A 'having an average fiber length of 51 mm (Apier R, manufactured by Unitika Ltd.), average denier 2.0 denier as a binder fiber, average fiber length 5
A core-sheath polyester composite short fiber B (manufactured by Unitika Ltd., trade name: Melty <2080>) having a softening point of 1 mm, a softening point of the sheath of 200 ° C., and a melting point of the core of 259 ° C. was used.

These para-aramid fibers A, meta-aramid fibers A ′ and core-sheath polyester conjugate short fibers B were
A ': B = 25: 25 : 50 uniformly cotton mixing at a rate of, and create a parallel web of 20 g / m ² and 40 g / m ² through the card. As an intermediate layer, parallel webs having a basis weight of 40 g / m ² were arranged so that the fiber arrangement was perpendicular to the machine direction, and parallel webs having a basis weight of 20 g / m ² were laminated on the upper and lower surfaces so that the fiber arrangement was in the machine direction. .

This laminated nonwoven web was placed on a 30-mesh wire mesh moving at a speed of 30 m / min, and subjected to high-pressure liquid flow treatment. The high-pressure liquid flow treatment uses a high-pressure liquid flow treatment device in which injection holes having a hole diameter of 0.12 mm are arranged in three groups with a hole interval of 0.62 mm, and the liquid flow is applied in two stages from a position 80 mm above the laminate. I let it. In the first stage treatment, the pressure was set to 20 kg / m ² as pre-entanglement, and in the second stage treatment, the pressure was 60 kg / m ² . The first-stage treatment was performed once from each side of the laminated nonwoven web, and the second-stage treatment was performed four times from each side of the laminated nonwoven web.

Then, after removing excess moisture from the treated laminated nonwoven web obtained by using a mangle roll, a drying treatment was carried out at a temperature of 98 ° C. by using a hot air drier, and subsequently, the heat was introduced into a hot pressing apparatus and heated. A pressure treatment was performed. That is,
Pressure contact area 0.25mm ² , Pressure contact density 16 contacts / cm ²
Guided between the embossing roll engraved on the surface and the flat roll, the surface temperature of the rolls is 185 ° C., the linear pressure between the rolls is 25 kg / cm, and the gap between the rolls is 50
μm and subjected to a heat-pressure treatment to obtain a heat-resistant nonwoven fabric of the present invention.

Example 2 Using the same fibers as in Example 1, para-aramid fiber A, meta-aramid fiber A ', core-sheath polyester conjugate short fiber B
Was obtained in the same manner as in Example 1 except that cotton was uniformly mixed at a ratio of A: A ': B = 30: 30: 40 to obtain a heat-resistant nonwoven fabric of Example 2 of the present invention.

Example 3 Using the same fibers as in Example 1, para-aramid fiber A, meta-aramid fiber A ', core-sheath polyester conjugate short fiber B
Was obtained in the same manner as in Example 1 except that cotton was uniformly mixed at a ratio of A: A ': B = 20: 20: 60 to obtain a heat-resistant nonwoven fabric of Example 3 of the present invention.

Example 4 Using the same fibers as in Example 1, para-aramid fiber A, meta-aramid fiber A ', core-sheath polyester composite short fiber B
Was obtained in the same manner as in Example 1 except that cotton was uniformly mixed at a ratio of A: A ′: B = 40: 40: 20 to obtain a heat-resistant nonwoven fabric of the present invention of Example 4.

Example 5 A heat-resistant nonwoven fabric of the present invention of Example 5 was obtained in the same manner as in Example 1 except that the basis weights of the parallel webs laminated on the upper and lower surfaces were each set to 30 g / m ² . .

Example 6 In Example 1, the basis weight of the parallel web of the intermediate layer was changed to 2
0 g / m ^2, and the basis weight of the parallel web laminated on the upper and lower surfaces was 15 g / m ² , respectively.
° C, linear pressure of roll 10 kg / cm, gap 50 between rolls
A heat-resistant nonwoven fabric of the present invention of Example 6 was obtained in the same manner as in Example 1 except that the thickness was changed to μm.

Comparative Example 1 In Example 1, the weight of the parallel web of the intermediate layer was changed to 3
And 0 g / m ^2, the basis weight of the parallel webs to be laminated on the upper and lower surfaces except for using 30 g / m ^2, respectively to obtain a heat-resistant nonwoven fabric of the present invention in Comparative Example 1 in the same manner as in Example 1.

Comparative Example 2 In Example 1, the weight of the parallel web of the intermediate layer was changed to 7
And 0 g / m ^2, except that the basis weight of the parallel webs to be laminated to the upper and lower surfaces was 15 g / m ² to obtain a heat-resistant nonwoven fabric of the present invention in Comparative Example 2 in the same manner as in Example 1.

Comparative Example 3 Comparative Example 3 was carried out in the same manner as in Example 1 except that the gap between the rolls was changed to 100 μm during the hot pressing process.
Was obtained.

Comparative Example 4 In Example 1, the average fineness was 2.
0 denier, average fiber length 51 mm, softening point 110 of sheath
The same as Example 1 except that the core-sheath polyester composite short fiber (manufactured by Unitika Ltd., trade name: Melty <4080>) having a core melting point of 259 ° C. and a roll surface temperature of 105 ° C. in the hot pressing treatment was used. Thus, a nonwoven fabric of Comparative Example 4 was obtained.

Comparative Example 5 In Example 1, a parallel web having a fiber mixing ratio of 60 g / m ² was prepared in the same manner as in Example 1. After applying a high-pressure liquid flow to the parallel web under the same conditions as in the first embodiment, the parallel web was subjected to a thermal pressure welding treatment under the same conditions as in the first embodiment, and a comparative example 5 was performed.
Was obtained.

Comparative Example 6 In Example 1, the non-woven web of the intermediate layer was disposed so that the fiber arrangement was in the machine direction, and the upper and lower surfaces of the non-woven web were arranged so that the fiber arrangement was in a direction perpendicular to the machine direction. A heat-resistant nonwoven fabric of the present invention of Comparative Example 6 was obtained in the same manner as in Example 1 except that the woven web was laminated.

Table 1 shows the performances of the nonwoven fabrics obtained in Examples 1 to 6 and Comparative Examples 1 to 6.

[0064]

[Table 1]

The heat-resistant nonwoven fabrics of Examples 1 to 6 were free from spots, and had excellent mechanical properties and excellent dimensional stability at high temperatures.

The nonwoven fabric of Comparative Example 1 in which the nonwoven web of the intermediate layer has a basis weight ratio of less than 40% by weight has a tensile strength ratio (MD / CD) of the obtained nonwoven fabric of more than 1.5, and has a strength in the machine direction. The non-woven fabric was poor in the balance in the transverse direction, had a large shrinkage in the transverse direction at high temperature, and was inferior in dimensional stability.

The nonwoven fabric of Comparative Example 2 in which the weight ratio of the nonwoven web of the intermediate layer exceeds 50% by weight, the tensile strength ratio (MD / CD) ratio of the obtained nonwoven fabric is smaller than 1.0, The nonwoven fabric was not only poor in the balance in the lateral direction, but also had a large shrinkage in the lateral direction at high temperatures and was inferior in dimensional stability.

The gap between the rolls should be 100
The nonwoven fabric of Comparative Example 3 having a thickness of μm was excellent in mechanical properties and dimensional stability, but was bulky and was not an object of the present invention.

The softening point of the sheath of the binder fiber is 180 ° C.
The nonwoven fabric of Comparative Example 4, which is less than 1, has a high shrinkage rate at high temperature, causes wrinkles, and has a partially melted nonwoven fabric surface, and is inferior in dimensional stability and shape retention at high temperature. It did not withstand the intended use of the present invention.

The nonwoven fabric of Comparative Example 5 using a parallel web in which the fibers were arranged only in the machine direction had a large difference between the tensile strength ratio in the machine direction and the transverse direction, and the shrinkage in the transverse direction at high temperatures. The nonwoven fabric was large and had poor dimensional stability.

The nonwoven fabric of Comparative Example 6, in which the nonwoven web of the intermediate layer was disposed so that the fiber arrangement was in the machine direction, and the upper and lower layers thereof were disposed in the direction orthogonal to the machine direction, Distortion of the fibers constituting the uppermost layer occurred, and spots were observed.

[0072]

According to the present invention, a non-woven web having a parallel arrangement composed of a main fiber having a decomposition point of 300 ° C. or more and a binder fiber composed of a core-sheath composite short fiber having a softening point of a sheath component of 180 ° C. or more is prepared. A nonwoven web having a basis weight of the nonwoven fabric of 40 to 50% by weight is disposed as a layer so that the fiber arrangement is orthogonal to the machine direction.
5% by weight non-woven web is laminated so that the fiber arrangement is in the machine direction. The non-woven web is formed by non-woven fabric by hydroentanglement and hot pressing.
A nonwoven fabric having excellent dimensional stability and heat resistance can be obtained.

Claims (6)

[Claims] 1. A binder fiber comprising a core-sheath composite short fiber having a softening point of a main fiber having a decomposition point of 300 ° C. or more and a sheath component of 180 ° C. or more and a melting point difference of a sheath component and a core component of 30 ° C. or more. Is a nonwoven fabric which is entangled by high-pressure liquid flow treatment, and the intersections between the fibers constituting the web are entirely or partially thermally fused by thermocompression bonding, and comprises layers 1 to 5 satisfying the following conditions. The arrangement of the constituent fibers in each layer is continuously changed between the layers, and the bulk density is 0.1 to
0.7 g / cm ³ , and the ratio (MD / CD) of tensile strength between the machine direction (MD) and the cross direction (CD) of the nonwoven fabric was 1.
The shrinkage of the nonwoven fabric after leaving it in the constant temperature air at 150 ° C. for 2 hours is 3% in both the machine direction and the transverse direction.
A heat-resistant nonwoven fabric characterized by the following. Layer 1: The arrangement of the constituent fibers is mainly in the machine direction. Layer 2: The arrangement of the constituent fibers in the machine direction and the arrangement in the transverse direction are mixed. Layer 3: The arrangement of the constituent fibers is mainly in the horizontal direction. Layer 4: The arrangement of the constituent fibers in the machine direction and the arrangement in the transverse direction are mixed. Layer 5: The arrangement of the constituent fibers is mainly in the machine direction. 2. A nonwoven fabric comprising 40 to 80% by weight of a main fiber,
The heat-resistant nonwoven fabric according to claim 1, comprising 60 to 20% by weight of a binder fiber. 3. The heat-resistant nonwoven fabric according to claim 1, wherein the main fiber is an aromatic polyamide short fiber. 4. The binder fiber according to claim 1, wherein the binder fiber is a core-sheath conjugate short fiber comprising a copolyester having a softening point of 180 ° C. or higher as a sheath component and polyethylene terephthalate or a polyester mainly composed of the same as a core component. Claim 1
4. The heat-resistant nonwoven fabric according to any one of items 3 to 3. 5. A binder fiber comprising a core-sheath composite short fiber having a softening point of a main fiber having a decomposition point of 300 ° C. or more and a softening point of a sheath component of 180 ° C. or more and a melting point difference of a sheath component and a core component of 30 ° C. or more. To form a nonwoven web, and a nonwoven web having a basis weight of the nonwoven fabric of 40 to 50% by weight is placed on the intermediate layer so that the fiber arrangement is perpendicular to the machine direction. A laminated nonwoven web obtained by laminating ２５25% by weight of a nonwoven web such that the fiber arrangement is in the machine direction is entangled by a high-pressure liquid flow, and then the (softening point −10 ° C.) of the sheath component of the binder fiber is 〜 (Softening point + 50 ° C.), heat-welding treatment is performed and the whole or part is heat-sealed, the bulk density of the nonwoven fabric is 0.1 to 0.7 g / cm ³ , and the machine direction of the nonwoven fabric (MD ) And transverse tensile (CD) tensile strength ratio (MD / CD) Is made to be 1.0 to 1.5. 6. The mixing ratio of the main fiber and the binder fiber (main fiber: binder fiber) is from 40:60 to 80: 2.
The method for producing a heat-resistant nonwoven fabric according to claim 5, wherein the weight ratio is set to 0 (weight ratio).