JP2010121261A - Laminated nonwoven fabric - Google Patents

Abstract

The present invention provides a laminated nonwoven fabric that does not peel when stretched, has excellent followability, has high elongation, and is excellent in thermoformability, filter properties, and barrier properties.
SOLUTION: A thermoplastic long fiber layer having a birefringence of 0.040 or less is used as upper and lower layers, a thermoplastic fine fiber layer having an average fiber diameter of 2 μm or more is used as an intermediate layer, and the layers are integrated by thermal bonding. A laminated nonwoven fabric characterized by having
[Selection figure] None

Description

  The present invention relates to a laminated nonwoven fabric.

  Conventionally, a spunbond nonwoven fabric having high elongation and a spunbond nonwoven fabric having thermoformability are known, and are used in various fields and widely used. However, a nonwoven fabric having high elongation and excellent thermoformability has not been found in a laminated nonwoven fabric in which a fine fiber layer and a thermoplastic synthetic fiber layer are combined.

For example, Patent Document 1 discloses a method of obtaining a high-strength laminated nonwoven fabric excellent in filter properties and barrier properties by allowing fine melt-blown fibers to enter at least one surface with a penetration index of 0.36 or more into spunbond long fibers. Is disclosed.
However, when the melt blown fibers, which are fine fibers, are made to enter deeply into the spunbond long fibers, the strength of the laminated nonwoven fabric is increased, but there is a disadvantage that the form following property in molding is inferior and the elongation is inferior.

  In Patent Document 2, a melt blown fine fiber non-woven fabric and a spunbond long fiber non-woven fabric, which are prepared in advance, are laminated, and the laminated structure is integrated with a heat calender roll or a heat embossing roll. An excellent composite nonwoven fabric is disclosed.

  However, in the method described in Patent Document 2, the constituent fibers of the nonwoven fabric are rigidly fixed in each nonwoven fabric structure, and there is no degree of freedom. Therefore, the fine fibers of the laminated melt blown nonwoven fabric diffuse into the spunbond long fiber layer. Without causing the laminate to pass between the heat calender roll or the heat embossing roll, each nonwoven fabric suffers multiple thermal histories, so the strength and elongation of the nonwoven fabric decrease, and the spunbond layer There is a problem of delamination in the meltblown layer.

  Furthermore, since the nonwoven fabric described in Patent Document 2 is a melt-blown nonwoven fabric with a low basis weight, it is remarkably easily deformed and handling is complicated, and it is difficult to adjust the laminated structure, and in the process of processing, The microstructure is easily stretched and it is difficult to form a uniform layer.

Patent Document 3 discloses a nonwoven sheet having excellent thermoformability and filter characteristics. However, in order to have thermoformability, it is necessary to shrink the nonwoven sheet once with boiling water. There is no description about having thermoformability in a state where boiling water is not shrunk.
In addition, as in Patent Document 2, since the melt blown fine fiber nonwoven fabric and the spunbond long fiber nonwoven fabric, which have been adjusted in advance, are laminated and the laminated structure is integrated, it is difficult to adjust the laminate structure of the melt blown nonwoven fabric, It is difficult to form a uniform layer in the process of processing.

  In Patent Document 4, a laminated sheet of ultrafine fibers spun by melt blow is directly collected and formed on the upper surface of a spunbond long fiber nonwoven fabric to obtain a laminated sheet. A method for obtaining a composite non-woven fabric having good filter properties by applying is disclosed.

  In this composite nonwoven fabric, since the structure of the spunbond long fiber layer is fixed in advance by thermocompression bonding, the melt blown fine fiber is hardly penetrated into the long fiber layer and may be sufficiently entangled with the long fiber. Can not. Therefore, the anchor effect of fine fibers is insufficient, and it cannot be expected to provide sufficient resistance against delamination of the laminated structure.

WO2004 / 094136 Japanese Patent Laid-Open No. 7-207656 JP-A 63-235560 JP-A-2-289161

  The problem of the present invention is to solve the above-mentioned problems of the prior art, have high elongation, excellent air permeability, filter properties, barrier properties, extensibility at the time of molding, heat moldability, etc. It is to provide a laminated nonwoven fabric with good molding characteristics.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors set the birefringence of the thermoplastic long fibers constituting the upper and lower layers of the nonwoven fabric as a specific range, and specified the fiber diameter of the thermoplastic fine fibers of the intermediate layer In a state where the fiber surfaces of the thermoplastic long fibers and / or the fiber surfaces of the thermoplastic long fibers and the fiber surfaces of the thermoplastic fine fibers are slightly thermally bonded to each other and the fiber shape is substantially maintained. Through the integration, we have found a laminated nonwoven fabric that does not peel during stretch molding, has excellent followability, has high elongation, and has excellent thermoformability, filterability and barrier properties, and has reached the present invention. It is.

That is, the present invention is as follows.
1. A thermoplastic long fiber layer having a birefringence of 0.040 or less is used as upper and lower layers, a thermoplastic fine fiber layer having an average fiber diameter of 2 μm or more is used as an intermediate layer, and the layers are integrated by thermal bonding. Laminated nonwoven fabric.

2. 2. The laminated nonwoven fabric according to 1 above, wherein the thermoplastic long fibers and the thermoplastic fine fibers are polyester fibers.
3. 3. The laminated nonwoven fabric according to 1 or 2 above, wherein the thermal bonding is point bonding on a fiber surface of a thermoplastic long fiber layer.

4). 4. The laminated nonwoven fabric according to any one of the above 1 to 3, wherein the thermal bonding is point bonding between the fiber surface of the thermoplastic long fiber layer and the fiber surface of the thermoplastic fine fiber layer.
5). 5. The laminated nonwoven fabric according to any one of 1 to 4 above, wherein an average fiber diameter of the thermoplastic long fibers is 15 to 35 μm.

6). The laminated nonwoven fabric according to any one of the above 1 to 5, wherein the modulus of the laminated nonwoven fabric at an elongation of 100% at 100 ° C is 50 N / 3 cm or less.
7). The laminated nonwoven fabric according to any one of 1 to 6, wherein the laminated nonwoven fabric has a tensile elongation at 100 ° C of 100% or more.

  8). 8. A molded body obtained by integrally processing the laminated nonwoven fabric according to any one of 1 to 7 by thermoforming.

  The laminated nonwoven fabric of the present invention is composed of a layer of specific thermoplastic long fibers and a layer of thermoplastic fine fibers, the fiber surfaces of the thermoplastic long fibers, and the fiber surfaces of the thermoplastic long fibers and the thermoplastic fine fibers. The fiber surface is lightly heat-bonded and integrated. In addition, by increasing the amorphous nature of the thermoplastic long fibers and the thermoplastic fine fibers, the elongation of the fibers themselves and the nonwoven fabric is improved, and furthermore, since there are many amorphous parts, The thermoplastic fine fiber is thermally fused, and delamination is suppressed.

As a result, the laminated nonwoven fabric of the present invention does not peel when stretched, has excellent followability, has high elongation, and has excellent stretchability, thermoformability, filter properties, and barrier properties during molding. Good molding characteristics.
Therefore, the laminated nonwoven fabric of the present invention includes food materials such as food filters, air filters, liquid filters, vacuum cleaner filters, membrane supports, industrial materials such as filter materials, agricultural materials, soundproofing materials and sound absorbing materials. It can be suitably used for packaging materials such as desiccant wrapping materials and furnace wrapping materials.

The laminated nonwoven fabric of this invention WHEREIN: The schematic figure when the surface of the fiber in the entanglement point of thermoplastic long fibers mutually produces a splicing joint in the shape of a spot, and the state bonded in the shape of a spot is seen from the upper surface. It is. In the laminated non-woven fabric of the present invention, the fiber surface of the thermoplastic long fiber and the fiber surface of the thermoplastic fine fiber are bonded to each other in the form of dots, and is schematically shown when viewed from a cross section. It is a simple figure.

Hereinafter, the present invention will be described in detail.
The laminated nonwoven fabric of the present invention has the following characteristics.
(1) Since the degree of crystal orientation of the thermoplastic long fibers constituting the upper and lower layers of the laminated nonwoven fabric is kept low, it is possible to enhance the extensibility of the long fibers themselves and the extensibility of the laminated nonwoven fabric.

(2) Since the fiber diameter of the fine fibers in the intermediate layer is relatively large, the extensibility of the fine fibers themselves and the extensibility of the laminated nonwoven fabric can be improved.
(3) Since the laminated nonwoven fabric is lightly heat-bonded to form point-like adhesion on the fiber surface, and the weakly bonded parts are integrated with high frequency, the stretchability of the laminated nonwoven fabric is improved. Can do.

  Examples of the thermoplastic long fibers and the thermoplastic fine fibers constituting the laminated nonwoven fabric of the present invention include, for example, polyethylene fibers, polypropylene fibers, polyolefin fibers such as copolymer polypropylene, polyethylene terephthalate fibers, polybutylene terephthalate fibers, and polyethylene naphthalate fibers. Polyester fibers such as copolymer polyester, nylon-6 fibers, nylon-66 fibers, polyamide fibers such as copolymer nylon, and biodegradable fibers such as polylactic acid, polybutylene succinate, and polyethylene succinate. Used.

  Of these, from the viewpoint of heat resistance, polyester-based fibers are preferred as thermoplastic long fibers and thermoplastic fine fibers, and polyethylene terephthalate fibers are particularly preferred. The cross-sectional shape of the fiber is not particularly limited, and an irregular cross section such as a round shape, a flat shape, a C shape, a Y shape, or a V shape is used, and a round cross section is preferable.

  The thermoplastic long fiber constituting the nonwoven fabric of the present invention needs to have a birefringence (Δn) of 0.040 or less, more preferably 0.003 to 0.030, and particularly preferably 0.00. 005 to 0.020. When the birefringence index (Δn) is within this range, the elongation of the thermoplastic long fiber is large, the moldability is good, the thermal adhesiveness of the nonwoven fabric is improved, the surface fuzz is less, and the abrasion resistance is increased. Is improved. In the present invention, the birefringence (Δn) of the fiber can be in the above range by suppressing the orientation of the fiber molecules by spinning the fiber itself at a low speed.

  When the birefringence is larger than 0.040, the fiber crystallinity is high, the fiber elongation is lowered, the moldability is deteriorated, and heat setting at the time of heat bonding becomes difficult, and the surface fluff is suppressed. It becomes difficult. If the birefringence is less than 0.003, heat shrinkage occurs during thermocompression bonding, and the fibers are dissolved by the heat of the thermocompression bonding roll and taken up by the roll, making it difficult to produce a nonwoven fabric. .

  In the present invention, the thermoplastic continuous fiber preferably has an average fiber diameter of 15 μm to 35 μm, more preferably 20 μm to 30 μm. If the average fiber diameter is within this range, the elongation of the thermoplastic long fibers is large, and furthermore, in the thermal bonding process of the nonwoven fabric, heat fusion with the thermoplastic fine fibers improves the followability, and the moldability of the laminated nonwoven fabric. Becomes better.

  When the average fiber diameter is not smaller than 15 μm, the crystallinity of the fiber is high, the crystal part is increased, the elongation of the fiber is decreased, the moldability is liable to be deteriorated, and the heat-fusibility is decreased. Heat setting at the time of thermocompression bonding is likely to be difficult, and suppression of fluff on the nonwoven fabric surface is likely to be insufficient. When the average fiber diameter is larger than 35 μm, thermal shrinkage is likely to occur during thermocompression bonding, and it becomes difficult to produce a nonwoven fabric because the fibers are easily melted by the heat of the thermocompression bonding roll and taken up by the roll. There is.

  In the present invention, the thermoplastic fine fiber needs to have an average fiber diameter of 2 μm or more, preferably 2 μm to 10 μm, particularly preferably 3 μm to 8 μm. When the average fiber diameter is 2 μm or more, the elongation of the thermoplastic fine fiber is large, and further, in the thermal bonding process of the nonwoven fabric, it is thermally fused with the thermoplastic long fiber, the followability is improved, and the moldability of the laminated nonwoven fabric is improved. Becomes better.

  If the average fiber diameter of the thermoplastic fine fibers is less than 2 μm, the crystallinity of the fibers is increased, the elongation of the fibers is lowered, the moldability is deteriorated, and the heat-fusibility of the thermoplastic fine fibers is reduced. It becomes difficult to thermally bond the thermoplastic long fiber and the thermoplastic fine fiber at the time of heat bonding, so that the integral molding of the laminated nonwoven fabric becomes insufficient.

  In the present invention, the fineness of the thermoplastic long fiber is not particularly limited and may be any fineness corresponding to the above fiber diameter. However, the fineness of the thermoplastic long fiber is 0 in consideration of productivity and texture. .5 to 30 dtex is preferable, more preferably 1 to 20 dtex, and particularly preferably 3 to 10 dtex.

  Both the thermoplastic long fiber and the thermoplastic fine fiber are preferably made of low-stretched polyester fiber. The low-stretch fiber of the polyester fiber has a low degree of crystal orientation in the spinning process, has a low crystallinity, good stretchability, and can be highly stretched and highly stretched. In particular, as the thermoplastic long fiber, a low-crystallinity and low-orientation polyester fiber obtained at a low spinning speed of 1000 to 3500 m / min is preferably used.

The tensile elongation of the laminated nonwoven fabric of the present invention is preferably from 50 to 500%, more preferably from 70 to 400%. Thus, when the elongation is high, the hot stretch processing characteristics are improved.
Both the thermoplastic long fibers and the thermoplastic fine fibers constituting the laminated nonwoven fabric of the present invention are preferably low-orientation fibers, and the fiber surfaces of the thermoplastic long fibers and the length of the thermoplastic long fibers by heat. A low-orientation fiber having a feature that the fiber surface of the fiber and the fiber surface of the thermoplastic fine fiber are likely to be fused is preferable.

  By heating the laminated non-woven fabric as mentioned above, the fiber surfaces melt at the entanglement point of the fibers in the heating atmosphere and adhere to each other in the form of dots. The frequency that the part exists can be increased. Furthermore, since it is weaker than normal thermal bonding and can be uniformly stretched with a small stress, it becomes a laminated nonwoven fabric suitable for thermoforming with large stretch.

  The laminated nonwoven fabric of the present invention has a tensile elongation at 100 ° C. of preferably 100% or more, more preferably 120 to 500%, and particularly preferably 150 to 400%. The molding characteristics by press are good, and integrated processing by thermoforming becomes possible.

  In the laminated nonwoven fabric of the present invention, the modulus at an elongation of 100% at 100 ° C. is preferably 50 N / 3 cm or less, more preferably 1 to 40 N / 3 cm, still more preferably 1 to 30 N / 3 cm. Within this range, the thermoforming properties are good and uniform stretching can be performed with a small stress, which is suitable for thermoforming with large stretch.

Furthermore, depending on the purpose, one or two kinds of other resins, flame retardants, inorganic fillers, softeners, plasticizers, pigments, antistatic agents, etc. may be added to the thermoplastic long fibers and / or thermoplastic fine fibers. You may add more.
The basis weight of the laminated nonwoven fabric of the present invention is not particularly limited and can be selected according to the purpose of use. When used for normal purposes, the basis weight is about 5 to 300 g / m ² , but may be out of this range in some cases.

In the laminated nonwoven fabric of the present invention, the thermoplastic long fibers of the upper and lower layers (S layer) are preferably spunbond long fibers, and the thermoplastic fine fibers of the intermediate layer (M layer) are preferably melt blown fine fibers.
The laminated nonwoven fabric of the present invention preferably has an SMS structure, and the S layer may constitute upper and lower layers and the M layer may constitute an intermediate layer, such as SSMSS and SMMS.

In the laminated nonwoven fabric of the present invention, by using melt blown fine fibers as the thermoplastic fine fibers, filter performance and barrier performance by the melt blown fine fibers can be expressed more effectively. The amount of the melt blown fine fibers in the laminated nonwoven fabric is preferably 10 wt% or more in terms of the fine fibers or 2 g / m ² or more in terms of basis weight with respect to the whole laminated nonwoven fabric.

When the amount of the melt blown fine fiber is within the above range, the air permeability of the laminated nonwoven fabric of the present invention is 60 cm ³ / cm ² / second or less, more preferably 40 cm ³ / cm ² / second or less, particularly preferably 30 cm ³ / second. A laminated non-woven fabric excellent in filter performance and barrier performance can be obtained at a cm ² / second or less. In addition, since the melt blown fine fiber is uniformly stretched even after the laminated nonwoven fabric of the present invention is thermally stretched by molding, a molded body excellent in filter performance and barrier performance can be obtained.

The laminated nonwoven fabric of the present invention is characterized in that the fibers are integrated in a state where the fibers are slightly heat-bonded and the fiber shape is substantially maintained.
Usually, the fiber bond in the spunbonded nonwoven fabric is firmly bonded by thermocompression bonding, so the crimped part does not maintain the fiber shape, the fiber is in a crushed shape, and the fibers are fused together to form a film The embossed pattern is formed by dot-like surface adhesion.

  On the other hand, in the laminated nonwoven fabric of the present invention, a thermoplastic long fiber layer (S layer) and a thermoplastic fine fiber layer (M layer) are laminated in, for example, an SMS structure, and are subjected to temporary thermocompression bonding. It is heat-bonded in a state where it is suppressed.

  The method of temporary thermocompression bonding is not particularly limited, but preferably, a method using a pair of embossing rolls having a concavo-convex pattern on at least one surface, a method using a pair of flat rolls having a flat surface, and the like can be mentioned. A method of joining non-woven fibers such as a punch method or a spunlace method can also be used.

  Thus, by performing temporary thermocompression bonding and thermal bonding in two stages, the fiber bonding in the laminated nonwoven fabric of the present invention is limited to mild thermal bonding, and is mainly dot-shaped bonding on the fiber surface. That is, in the laminated nonwoven fabric of the present invention, as illustrated in FIG. 1 and FIG. 2, the fibers are bonded by point adhesion, so that the fiber shape is maintained, and the fibers are crushed like conventional products. Thus, the fiber is not in the form of a film fused together.

In the present invention, even if an embossed pattern is attached by temporary thermocompression bonding, heat shrinkage is developed microscopically around the embossed pattern due to the surface-suppressed thermal bonding in the second stage, and the embossed pattern comes off or While weakening, the fabric weight unevenness of the whole laminated nonwoven fabric is reduced. The second stage thermal bonding is not particularly limited as long as it is a thermal bonding method that suppresses the nonwoven fabric in a planar manner, but preferably a felt calender roll is used.
In the laminated nonwoven fabric of the present invention, the frequency at which the fibers are bonded to each other is determined by the number of entanglement points between the fibers and is not particularly limited, but is preferably a high frequency and weak bond.

Next, the manufacturing method of the laminated nonwoven fabric of this invention is demonstrated.
As a method for producing the laminated nonwoven fabric of the present invention, a conventionally known spunbond method and melt blow method are preferably used.
Conventional non-woven fabrics of spunbond fibers and meltblown fibers use embossed rolls with an uneven surface, and are partially thermocompression bonded, and the fiber web is fused and bonded into a film shape according to the embossed handle shape. The sheet-like material which has is obtained. However, when the film is highly stretched, the film obtained by thermocompression bonding according to the pattern shape of the emboss may break, and it is difficult to obtain a laminated nonwoven fabric with a high elongation.

In order to solve the above problems, in the laminated nonwoven fabric of the present invention, the above problems were solved by performing thermal bonding in two stages.
In the laminated nonwoven fabric of the present invention, the thermal bonding is performed by first using a pair of embossed rolls having a concavo-convex pattern on at least one surface, and a linear pressure of 50 at a roll temperature of 30 to 120 ° C, preferably 50 to 100 ° C. A laminated nonwoven fabric that has been preliminarily thermocompression bonded is obtained by heat bonding under ˜1000 N / cm, preferably 200 to 700 N / cm.

  Next, as shown in FIG. 1, the laminated nonwoven fabric subjected to temporary thermocompression bonding is heat-bonded at a roll temperature of 80 to 150 ° C., preferably 100 to 140 ° C., using a felt calender roll. The fiber surfaces melt at the entanglement points between the long fibers and adhere to each other in the form of dots, and the frequency at which the bonded portions exist can be increased.

  In addition, as shown in FIG. 2, at the entanglement point of the thermoplastic long fiber and the thermoplastic fine fiber, the surface of the fiber melts and adheres to each other in the form of dots, and the frequency of the existence of the bonded portion may be increased. it can. Furthermore, since these point-like adhesions are weaker than ordinary thermocompression bonding, uniform stretching can be performed with a small stress, which is suitable for thermoforming with large expansion.

  The laminated nonwoven fabric of the present invention can be integrally processed by thermoforming to form a molded body. There is no restriction | limiting in particular about the shape of a molded object, It is preferable to select according to the intended purpose, such as a semicircle, a cylinder shape, and a rectangle.

The expansion ratio in thermoforming is preferably in the range of 0.05 to 1.5, more preferably in the range of 0.1 to 1.0. The molding development ratio is set by measuring a depth of a molded body when a 20 cm × 20 cm sample piece is set in a molding machine, preheated at a hot air temperature of 150 ° C., and hot pressed with a molding die having a diameter of 12 cm, It is a value defined by the following formula (1) obtained by dividing the depth of the molded body by the diameter of the molded sheet.
Deployment ratio = (depth of molded body) / (diameter of sheet before molding) (1)

  That is, in integral processing by thermoforming, the expansion ratio indicates the ratio between the diameter and the molding depth when a sheet-like material is thermoformed into a cup shape, and is an index that indicates the degree of molding, and is usually developed. When the ratio is 1, the actual draw ratio is about 3 times.

Hereinafter, the present invention will be described in more detail with reference to examples.
Measurement methods, evaluation methods, etc. are as follows.
(1) Fineness (dtex: decitex)
Except for 10 cm at both ends of a fabric sample such as a non-woven fabric, an appropriate number of fibers were sampled from an area of 20 cm width of the fabric, the mass of 100 cm was measured, and the following formula was calculated.
Fineness (dtex) = {[mass (g)] / [number of fibers]} × 10000

(2) Average fiber diameter (μm)
Except for 10 cm at both ends of a fabric sample such as a non-woven fabric, an appropriate number of fibers are sampled from an area of every 20 cm width of the fabric, and the diameter of each fiber is measured at 30 points with a microscope. The average value of the measured values was calculated and used as the average fiber diameter.

(3) Tensile elongation (%)
It measured based on JIS L-1906. Except for 10 cm at both ends of a fabric sample such as a non-woven fabric, 5 samples having a width of 5 cm and a length of 20 cm per 20 cm width were cut in the longitudinal direction and measured with a tensile tester at a gripping interval of 10 cm and a tensile speed of 30 cm / min. The tensile elongation was calculated by averaging the measured values of the five samples.

(4) Modulus at 100% elongation at 100 ° C. (N / 3 cm)
Except for 10 cm at both ends of a fabric sample such as a non-woven fabric, 5 samples having a width of 3 cm and a length of 10 cm per 20 cm width are cut out in the longitudinal direction, using a tensile tester, a grip interval of 2 cm, a pulling speed of 20 cm / min, and a temperature of 100 ° C. Under these conditions, the modulus (N / 3 cm) at an elongation of 100% was measured. The modulus was calculated by averaging the measured values of five samples.

(5) Tensile elongation at 100 ° C (%)
Except for 10 cm at both ends of a fabric such as a nonwoven fabric, 5 samples of a width of 3 cm and a length of 10 cm per 20 cm width are cut out in the longitudinal direction, and a tensile tester is used to hold the grip at an interval of 2 cm, a tensile speed of 20 cm / min, and a temperature of 100 ° C. Measured under conditions. The tensile elongation (%) was calculated by averaging the measured values of five samples. Each longitudinal direction was measured and the average value was calculated.

(6) Air permeability (cm ³ / cm ² / sec)
It measured based on the fragile method described in JIS L-1096. Except for 10 cm at both ends of a fabric such as a non-woven fabric, one point was collected per 20 cm width and measured, and the average value of the measured values of five samples was calculated.

(7) Birefringence (Δn)
Using a polarizing microscope, it is possible to measure the distribution of the average refractive index observed from the side of the fiber by the interference fringe method. This method can be applied to fibers having a circular cross section. The refractive index of the fiber is characterized by the refractive index n || for polarized light having an electric field vector parallel to the fiber axis and the refractive index n⊥ for polarized light having an electric field vector perpendicular to the fiber axis. Δn = (n || −n⊥).

When the fiber is irradiated with polarized light, it is divided into two polarized lights that vibrate at right angles to each other. Since the refractive index of the fiber differs depending on the axial direction, a difference occurs in the distance traveled by the two lights. This is retardation, which is represented by R, and when the fiber cross-sectional diameter is d ₀ , there is a relationship between the birefringence and the following equation.
R = d ₀ (n || −n⊥)

  Optically flat slides and cover glasses and encapsulants inert to the fibers were used. Several fibers were immersed in this encapsulant to prevent the single yarns from contacting each other. Further, the fiber axis was set so that the fiber axis was perpendicular to the optical axis of the polarizing microscope and the interference fringes. The interference fringe pattern was measured to obtain retardation, and the birefringence of the fiber was measured. Measurement was performed on 10 fibers of the sample, and an average value of 10 measured values was calculated.

(8) Evaluation of unfolding ratio and moldability in molding A fabric sample piece such as a 20 cm × 20 cm non-woven fabric was set in a molding machine, preheated at a hot air temperature of 150 ° C., and hot pressed with a molding die having a diameter of 12 cm. The depth of the molded body at the time was measured, and the expansion ratio was calculated by the following formula.
Deployment ratio = (depth of molded body) / (diameter of sheet before molding)
The moldability was evaluated based on the moldability at a development ratio of 0.5.
○: No breakage, good moldability ×: Breakage occurred, poor moldability

[Example 1]
Polyethylene terephthalate with a solution viscosity (ηsp / c) of 0.75 is extruded by the spunbond method at a discharge rate of 0.9 g / min · Hole and a spinning temperature of 300 ° C. with the filament group facing the moving collection surface. For the filament group thus obtained, a thermoplastic long fiber web having a spinning speed of 1,800 m / min, a fineness of 5 dtex, a circular cross section, and a basis weight of 38.5 g / m ² was prepared on the surface of the collection net.

On the other hand, polyethylene terephthalate having a solution viscosity (ηsp / c) of 0.50 was spun by a melt blow method under the conditions of a spinning temperature of 300 ° C., a heating air temperature of 320 ° C., and a discharge air of 800 Nm ³ / hour / m. The thermoplastic fine fiber having a fiber diameter of 3.3 μm was directly jetted toward the thermoplastic long fiber web prepared above as a random web having a basis weight of 23 g / m ² .

  At this time, the distance from the melt blow nozzle to the upper surface of the thermoplastic long fiber web was set to 100 mm, and the suction on the collecting surface immediately below the melt blow nozzle was set to 0.2 kPa and the wind speed was about 7 m / sec. Thus, a thermoplastic fine fiber web / thermoplastic long fiber web (abbreviated as MW / SW1) was prepared.

On this thermoplastic fine fiber web / thermoplastic long fiber web (MW / SW1) surface, a polyethylene terephthalate long fiber web was further spun in the same manner as the thermoplastic long fiber prepared first, and the thermoplastic long fiber was spun. A three-layer laminated web (SW2 / MW / SW1) composed of web / thermoplastic fine fiber web / thermoplastic long fiber web was obtained. The obtained three-layer laminated web had a total basis weight of 100 g / m ² and a ratio of thermoplastic fine fibers of 23 wt%.

Next, partial thermocompression bonding was performed on SW2 / MW / SW1 using a pair of embossing rolls having an uneven pattern on one surface. The embossing roll used had a convex unit area of 2 mm ² and a crimping area ratio of 18%, and was partially crimped at a roll linear pressure of 400 N / cm under conditions of an upper and lower roll temperature of 70 ° C.

Next, this partially crimped web was heat-treated with a felt calender (drum diameter 2500 mm, temperature 105 ° C., processing speed 15 m / min) to obtain a laminated nonwoven fabric.
The obtained laminated nonwoven fabric was set in a molding machine, preheated at a hot air temperature of 150 ° C., and hot-pressed with a molding die having a diameter of 12 cm to produce a molded body.

[Example 2]
A laminated nonwoven fabric with a total basis weight of 100 g / m ² was prepared in the same manner as in Example 1 except that the heat treatment temperature in the felt calender was 130 ° C., and a molded body was produced using the obtained laminated nonwoven fabric.

Example 3
Except that the basis weight of the thermoplastic long fiber layer was 44 g / m ² and the basis weight of the thermoplastic fine fiber layer was 12 g / m ² , the total basis weight was 100 g / m ² , and the thermoplastic fine fiber was the same as in Example 1. A laminated nonwoven fabric (SW2 / MW / SW1) having a layer ratio of 12 wt% was prepared, and a molded body was produced using the obtained laminated nonwoven fabric.

Example 4
A laminated nonwoven fabric having a total basis weight of 100 g / m ^{2 in} the same manner as in Example 1 except that the thermoplastic fine fiber layer was spun at an average fiber diameter of 7.5 μm under the condition of discharge air of 500 Nm ³ / hour / m. (SW2 / MW / SW1) was prepared, and a molded body was produced using the obtained laminated nonwoven fabric.

[Comparative Example 1]
A laminated nonwoven fabric (SW2 / SW1) having a total basis weight of 100 g / m ² was prepared in the same manner as in Example 1 except that only the thermoplastic long fiber layer was laminated without using the thermoplastic fine fibers in the intermediate layer, A molded body was manufactured using the laminated nonwoven fabric obtained.

[Comparative Example 2]
A laminated nonwoven fabric having a total basis weight of 100 g / m ^{2 in} the same manner as in Example 1 except that the thermoplastic fine fiber layer was spun at an average fiber diameter of 1.9 μm under conditions of discharge air of 1200 Nm ³ / hour / m. (SW2 / MW / SW1) was prepared. The resulting laminated nonwoven fabric had low elongation of the yarn and fabric of the thermoplastic fine fiber layer, and the thermoplastic fine fiber layer was torn during molding, and a molded product could not be obtained.

[Comparative Example 3]
Polyethylene terephthalate was spun at a spinning speed of 4,500 m / min in the same manner as in Example 1 to obtain a thermoplastic long fiber web (circular cross-section yarn, fineness 2 dtex). Using the same embossing roll as in Example 1, the resulting thermoplastic long fiber web was partially crimped at an upper and lower roll temperature of 235 ° C. and a roll linear pressure of 400 N / cm to obtain a nonwoven fabric having a total basis weight of 100 g / m ^2. It was.
The obtained nonwoven fabric had low yarn and fabric elongation, and the nonwoven fabric was torn during molding, and a molded body could not be obtained.
Table 1 shows the measurement and evaluation results in the above Examples and Comparative Examples.

From Table 1, the following is clear.
It turns out that the laminated nonwoven fabric of the Example of this invention has low air permeability compared with the thing of the comparative example 1, and is excellent in filter performance and barrier performance. Moreover, after molding, the air permeability is similarly low, and it can be seen that the molded body is excellent in filter performance and barrier performance.

  It can be seen that the laminated nonwoven fabrics of the examples of the present invention have higher fabric elongation and excellent moldability than Comparative Examples 2 and 3. Moreover, if the elongation of either the thermoplastic long fiber layer or the thermoplastic fine fiber layer is low, the elongation as a laminated nonwoven fabric is low, and both the thermoplastic long fiber and the thermoplastic fine fiber have an amorphous part. It is necessary to have the fibers, and when the fibers are thermally bonded to each other, they can be heat-sealed to suppress delamination, have excellent followability, and can be molded by stretching.

  In addition, the laminated nonwoven fabric of the present invention has a low modulus at 100% elongation at 100 ° C., good thermoforming properties, and can be uniformly stretched with a small stress. Is possible.

  The laminated non-woven fabric of the present invention is excellent in filterability and barrier properties as well as moldability, food materials, air filters, liquid filters, vacuum cleaner filters, filter materials such as membrane supports, industrial materials including filter materials, It can be suitably used for packaging materials such as agricultural materials, soundproofing materials, sound-absorbing materials, desiccant packaging materials, and furnace packaging materials.

DESCRIPTION OF SYMBOLS 1 Thermoplastic long fiber 2 Fusion splicing part of thermoplastic long fibers 3 Thermoplastic fine fiber 4 Fusion splicing part of thermoplastic long fiber and thermoplastic fine fiber

Claims (8)

  A thermoplastic long fiber layer having a birefringence of 0.040 or less is used as upper and lower layers, a thermoplastic fine fiber layer having an average fiber diameter of 2 μm or more is used as an intermediate layer, and the layers are integrated by thermal bonding. Laminated nonwoven fabric.   The laminated nonwoven fabric according to claim 1, wherein the thermoplastic long fibers and the thermoplastic fine fibers are polyester fibers.   The laminated nonwoven fabric according to claim 1 or 2, wherein the thermal bonding is point bonding on a fiber surface of a thermoplastic long fiber layer.   The laminated nonwoven fabric according to any one of claims 1 to 3, wherein the thermal bonding is point bonding between a fiber surface of a thermoplastic long fiber layer and a fiber surface of a thermoplastic fine fiber layer.   The laminated nonwoven fabric according to any one of claims 1 to 4, wherein an average fiber diameter of the thermoplastic long fibers is 15 to 35 µm.   The laminated nonwoven fabric according to any one of claims 1 to 5, wherein the laminated nonwoven fabric has a modulus at an elongation of 100% at 100 ° C of 50 N / 3 cm or less.   The laminated nonwoven fabric according to any one of claims 1 to 6, wherein the laminated nonwoven fabric has a tensile elongation at 100 ° C of 100% or more.   A molded body obtained by integrally processing the laminated nonwoven fabric according to any one of claims 1 to 7 by thermoforming.

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