JP3165758B2 - Polypropylene long fiber non-woven fabric - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polypropylene-based long-fiber nonwoven fabric which is excellent in heat shrinkability, shape retention during thermoforming and lightweight.

[0002]

2. Description of the Related Art Conventionally, as a non-woven fabric made of thermoplastic synthetic long fibers having excellent heat shrinkability, a non-woven fabric made of low-oriented polyester long fibers obtained by reducing the melt spinning speed to near the lower limit has been known. ing. However, this non-woven fabric has the problem that the polyester fiber itself having a low degree of orientation is brittle to heat because of its low orientation, and the abrasion resistance of the non-woven fabric is inferior. Since it is made of a large polyester fiber, there is also a problem that the lightness is inferior when made into a nonwoven fabric. On the other hand, as other nonwoven fabrics made of thermoplastic synthetic filaments with excellent heat shrinkability, crimped filaments obtained by melt-composite spinning of different shrinkage polymer components or spun filaments immediately after melt spinning are cooled. Nonwoven fabrics comprising crimped long fibers obtained by performing asymmetric cooling are known. However, these nonwoven fabrics have a problem that shape retention is remarkably inferior when thermoformed due to low heat shrinkage stress.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems and is excellent in heat shrinkability, shape retention during thermoforming and light weight. An object is to provide a polypropylene-based long-fiber nonwoven fabric suitable as a material.

[0004]

Means for Solving the Problems The present inventors have made intensive studies to solve the above-mentioned problems, and as a result, have reached the present invention. That is, the present invention comprises only a polypropylene copolymer obtained by random copolymerization of 92% by weight or more and 97% by weight or less of propylene and 3% by weight or more and 8% by weight or less of ethylene, and has a melt flow rate of 15 g. / 10 minutes or more 8
0 g / 10 minutes or less, a single fiber fineness of 10 denier or less, of produced by spunbond method strength of at least 50 wt.% Containing as components a 2 g / denier or more long fiber
At least the long fibers in the nonwoven fabric are partially thermally bonded to each other at an adhesion area ratio of 3% or more and 50% or less, and a dry heat area shrinkage ratio at a temperature of 100 ° C. of 15% or more. The present invention is characterized by a polypropylene-based long-fiber nonwoven fabric, which is characterized in that there is a nonwoven fabric. Further, the present invention is the polypropylene-based copolymer, especially the Q value (weight average molecular weight / number average molecular weight) is 8 or less
The present invention provides a polypropylene-based long-fiber nonwoven fabric.

Next, the present invention will be described in detail. The long fiber constituting the nonwoven fabric of the present invention is at least 92% by weight and 97% by weight.
It is composed of a polypropylene copolymer in which the following propylene and 3% by weight to 8% by weight of ethylene are randomly copolymerized. In this copolymer,
The copolymerization of ethylene has a significant effect on the drop in the melting point and the heat shrinkage of the copolymer, lowering the melting point of the copolymer in proportion to the copolymerization amount and increasing the heat shrinkage. If the copolymerization amount is less than 3% by weight, the decrease in the melting point of the copolymer becomes small,
It is not preferable because the heat shrinkage rate when the long fiber is heat-treated decreases. On the other hand, if the copolymerization amount exceeds 8% by weight, the rate of formation of by-products soluble in the polymerization solvent (hydrocarbon) during polymerization increases, and the productivity decreases, which is not industrially uneconomical. Therefore, in the present invention, this copolymerization amount is set to 3% by weight or more and 8% by weight or less, preferably 3.2% by weight or more and 7.0% by weight or less, particularly preferably 3.5% by weight or more and 6.0% by weight or less. The following is assumed. This copolymer is obtained by random copolymerization of the above-mentioned 3% by weight to 8% by weight of ethylene with 92% by weight to 97% by weight of propylene.
It is extremely important in terms of uniform heat shrinkage characteristics and spinnability of the copolymer. Another form of copolymerization is block copolymerization. In this copolymerization, the heat shrinkage characteristics of the copolymer become non-uniform because the structural units of ethylene are present in block units in the structure of polypropylene. It is not preferable because a problem that the spinnability is extremely lowered occurs.

The copolymer preferably has a Q value (weight average molecular weight / number average molecular weight) of 8 or less. The Q value is the ratio of the weight average molecular weight to the number average molecular weight of the polymer determined by gel permeation chromatography, and the melt-weighed polymer is collected before spinning, and the cooled polymer is collected. This is a value measured as a sample. It is known that a polypropylene polymer is easily deteriorated by the influence of heat and shear applied during melt spinning, and the Q value after melt spinning is lower than that before spinning. The Q value indicates the width of the molecular weight distribution and has a great influence on the suitability for production and processing of long fibers. In other words, if the Q value is large and the molecular weight distribution is wide, the processing temperature range for forming a nonwoven fabric using the obtained long fibers is widened, and not only can a nonwoven fabric of stable quality be obtained,
The same effect can be obtained when performing thermoforming on the obtained nonwoven fabric. However, when the Q value increases and the width of the molecular weight distribution becomes too wide, the yarn cooling during melt spinning deteriorates, and the spinnability decreases. Therefore,
In the present invention, the Q value is set to 8 or less, preferably 7.5.
The value is particularly preferably 7.0 or less.

The long fibers constituting the nonwoven fabric of the present invention have a melt flow rate of 15 g / 10 min or more and 80 g / 1.
Less than 0 minutes. The melt flow rate value of the long fiber is measured by the method described in ASTM D1238 (L).
If it is less than 5 g / 10 minutes, the heat shrinkage stress of the long fiber becomes high and the heat shrinkage and bulkiness can be increased, but not only the spinnability of the polymer but also the heat drawability in the next step are reduced. In addition, since the spinning temperature during melt spinning is set high, the polypropylene polymer is decomposed and a large amount of gas is generated, which undesirably deteriorates the environment of the spinning chamber. on the other hand,
If the melt flow rate exceeds 80 g / 10 minutes, the heat shrinkage of long fibers is reduced, so that a nonwoven fabric having excellent heat shrinkage cannot be obtained, and the degree of polymerization of the polypropylene polymer is too low. Decomposes and generates a lot of gas,
It is not preferable because the environment of the spinning chamber is deteriorated. Therefore, in the present invention, this melt flow rate value is set to 1
5 g / 10 min to 80 g / 10 min, preferably 18 g / 10 min to 70 g / 10 min, particularly preferably 20 g / 10 min to 60 g / 10 min.

The long fibers constituting the nonwoven fabric of the present invention have a single fiber fineness of 10 denier or less. If the single fiber fineness exceeds 10 denier, the softness of the nonwoven fabric is reduced, an unusual coarse hardness is generated, and it is difficult to reduce the weight per unit area. It is not preferable because the cooling is insufficient and fusion occurs between the filaments to lower the spinnability.

The long fibers constituting the nonwoven fabric of the present invention have a strength of 2 g / denier or more. This strength is 2
If it is less than g / denier, it is not preferable because practically sufficient strength cannot be obtained when the nonwoven fabric is used. For example, when a non-woven fabric is made using this long fiber and the obtained non-woven fabric is thermoformed into a container protection filter, it becomes difficult to provide the filter with sufficient strength for practical use. is there.

The nonwoven fabric of the present invention contains at least 50% by weight of the long fibers as a constituent element. The nonwoven fabric contains, as other constituent elements, long fibers made of a polypropylene-based copolymer which does not satisfy the constituent requirements of the present invention and other ordinary fiber-forming thermoplastic synthetic long fibers. Should be less than 50% by weight. That is, in this nonwoven fabric, it is necessary to contain at least 50% by weight of the long fiber, and if the content is less than 50% by weight, the present invention can provide a nonwoven fabric with excellent heat shrinkability aimed at. Because you can't.

[0011] The nonwoven fabric of the present invention is one in which at least the polypropylene long fibers in the nonwoven fabric are partially thermally bonded to each other. The term "partial heat bonding" as used herein means that the polypropylene long fibers form a regular bonded portion. In this partial thermal bonding, the thermal bonding area per minimum repeating unit area in the nonwoven fabric is expressed as a percentage, that is, the bonding area ratio is 3% or more and 50% or less, and if this bonding area ratio is less than 3%. On the other hand, if the bonded area ratio exceeds 50%, the degree of freedom of unfixed long fibers in the nonwoven fabric is reduced, and the heat shrinkability of the nonwoven fabric is reduced. Neither is preferred. Therefore, in the present invention, the bonding area ratio is set to 3% or more and 50% or less, preferably 4% or more and 30% or less. The partial heat bonding portion is formed using, for example, a hot embossing roller or an ultrasonic welding machine. When using a hot emboss roller,
The shape of the partially heat-bonded portion is determined by the shape of the tip end surface of the engraving roller in the embossing machine, and can be any shape such as a round shape, an elliptical shape, a diamond shape, a triangular shape, a triangular shape, a T shape, a negative shape, a well shape, or a lattice shape. It can be.

The nonwoven fabric of the present invention has a dry heat area shrinkage at a temperature of 100 ° C. of 15% or more. The dry heat area shrinkage is a percentage of the area ratio of the non-woven fabric which has been heat-treated using an air oven type heat treatment machine at a processing temperature of 100 ° C. × a processing time of 15 minutes to the non-woven fabric before the heat treatment. The higher the thermal area shrinkage, the better the shape retention during thermoforming. If the dry heat area shrinkage is less than 15%, a nonwoven fabric having excellent heat shrinkability and excellent shape retention during thermoforming cannot be obtained, which is not preferable. Therefore, in the present invention, the dry heat area shrinkage is set to 15%, preferably 20% or more.

The nonwoven fabric of the present invention has a basis weight of 10 g / m2 for a thermoforming material such as a container protection filter.
^It is preferable that the amount be ² or more and about 150 g / m ² or less, but it can be appropriately determined according to the application and is not particularly limited.

The nonwoven fabric of the present invention can be efficiently produced by the so-called mixed fiber spunbonding method. First, after the polypropylene-based copolymer A is melted, it is spun from the spinning hole of A alone in the spinneret pack. On the other hand, the polypropylene-based copolymer B which does not satisfy the constitutional requirements of the present invention or other ordinary fiber-forming materials is used. After the thermoplastic synthetic polymer B is melted, it is spun from the spinning hole of B alone in the same spinneret pack as above, and the spun filaments A and B are cooled by a cooling device. The web is opened by a fiber opening means such as electric discharge and deposited on a moving conveyor to form a web. Alternatively, after melt spinning and cooling in the same manner as described above, the fiber is drawn by a drawing roller, drawn between the drawing roller and a drawing roller disposed downstream of the drawing roller, and spread by a fiber opening means such as corona discharge. And is deposited on a moving conveyor to form a web. At the time of melt spinning, the ratio of the weight of the copolymer A to the total weight of the copolymer A and the polymer B is at least 50%. In addition, this weight ratio is 100%
That is, when it is desired to obtain a nonwoven fabric composed of only the polymer A, the supply of the polymer B to the process may be stopped.

As the polypropylene-based copolymer used in the production of the nonwoven fabric of the present invention, those having a fiber-forming property and usually commercially available as a fiber grade can be used. Resin or a copolymerized polypropylene resin obtained by substantially random copolymerizing ethylene and propylene with the Ziegler-Natta catalyst so as to have the above-mentioned respective component ratios may be mentioned. In addition, the fiber grade referred to here is one that can be melt-spun with good spinnability. It should be noted that a matting agent, a light-fast agent, a heat-resistant agent, a pigment or the like usually used for fibers can be added to the polymer as long as the effects of the present invention are not impaired.

Further, the melt spinning can be performed by using an ordinary composite spinning apparatus. At the time of melt spinning, a copolymer having a melt flow rate of 10 g / 10 min or more and 80 g / 10 min or less is used as the copolymer A, and the melt flow rate of the obtained continuous fiber of the copolymer is 15 g.
It is necessary to carry out the melt spinning so as to be / 10 min or more and 80 g / 10 min or less. As a result, the heat shrinking force of the long fibers is improved, and a nonwoven fabric having excellent heat shrinkage can be obtained. In addition, not only the spinnability during melt spinning but also the heat stretchability in the next step is improved. Further, at the time of drawing, the drawn undrawn filament is hot drawn at a temperature of 40 ° C. or higher and at a temperature at which the fibers are not fused to each other. If the stretching temperature is lower than 40 ° C., the stretching tension becomes too high and the stretchability is lowered, and the stretching apparatus is undesirably expensive. On the other hand, the stretching temperature is at most lower than the temperature at which the long fibers start to fuse together. If the drawing temperature is too high and the fibers start to fuse with each other, yarn breakage will occur in the drawing process and the operability will decrease, or the quality of the product will decrease due to the lower uniformity of the product, which is not preferable. . Therefore, the drawing temperature is set to 40 ° C. or higher and a temperature at which the fibers are not fused to each other, preferably 60 to 100 ° C.

Next, the obtained web has a bonding area ratio of 3%.
By performing the thermal bonding treatment at a rate of 50% or less, at least the long fibers in the web are partially thermally bonded to each other. When performing the partial thermal bonding, for example, a hot embossing roller can be used. In this case, the processing temperature is set to a temperature lower than the melting point of the polypropylene copolymer, and the linear pressure of the roller is set to 50 kg / cm or less. And If the treatment temperature is equal to or higher than the melting point of the copolymer, the web may adhere to the roll during the treatment, and the operability is undesirably reduced. Therefore, the treatment temperature is set to a temperature lower than the melting point of the copolymer, preferably lower than the melting point by 10 ° C. or more. Also, an ultrasonic welding machine can be used. This ultrasonic welding machine is an apparatus for fusing fibers between fibers by, for example, vibration of an ultrasonic wave having a frequency of about 20 kHz. Therefore, the form of the nonwoven fabric is maintained while maintaining the heat shrinkability of the long fiber, and a nonwoven fabric having excellent heat shrinkage can be obtained.

In the present invention, as described above, a web composed of drawn filaments can be used as a nonwoven fabric raw material.
In this case, since the long fiber made of the polypropylene copolymer is oriented and stretched, and has a structure in which the crystal region grows together and the amorphous region increases, the web is subjected to the thermal bonding treatment as described above. When a nonwoven fabric is used, a nonwoven fabric with further improved heat shrinkability up to at least 20% can be obtained. It is preferable to use the above-mentioned ultrasonic welding machine when performing a heat bonding treatment on a web made of such drawn long fibers, since a nonwoven fabric with further improved heat shrinkability can be obtained.

[0019]

Next, the present invention will be specifically described based on examples. The measurement and evaluation of various characteristics in the examples were performed by the following methods. Melting point of polymer: Differential scanning calorimeter D manufactured by PerkinElmer
The melting point was defined as the temperature at which an extreme value of the melting heat absorption curve measured at a heating rate of 20 ° C./min using SC-2 type. Melt flow rate value (g / 10 minutes): ASTM D
It was measured by the method described in 1238 (L). Tensile strength (g / denier) and elongation (%) of fiber:
Toyo Baldwin's Tensilon UTM-4-1-1
Using 00, a sample having a sample length of 2 cm was measured at a tensile speed of 2 cm / min. Dry heat shrinkage of fiber (%): A total of 15 fibers are used as a sample.
Initial load 2mg / denier length L for each single fiber
₁ (cm), and then heat treated in an air oven type heat treatment machine at 100 ° C. for 15 minutes to obtain a length L ₂ (c)
m) was measured, the shrinkage was calculated by the following equation (a), and the average value was defined as the dry heat shrinkage. Dry heat shrinkage (%) = (L ₁ −L ₂ ) × 100 / L ₁ (a) KGSM tensile strength of nonwoven fabric (kg / 5 cm): Tensilon UTM-4 manufactured by Toyo Baldwin Co., Ltd. According to the stripping method described in JIS L-1096A, a test piece having a sample length of 10 cm and a sample width of 5 cm was measured at a tensile speed of 10 cm / min, and the average value of the obtained tensile strength was measured for the nonwoven fabric. in terms of the per basis weight of 100g / m ^2, KGS
M tensile strength (kg / 5 cm). Tensile elongation (%) of nonwoven fabric: JIS L-1 using Tensilon UTM-4-1-100 manufactured by Toyo Baldwin Co., Ltd.
According to the stripping method described in No. 096A, the sample length was 10
cm and a sample width of 5 cm were measured at a tensile speed of 10 cm / min. Dry heat area shrinkage rate (%) of nonwoven fabric: A total of four sample pieces each having a sample length of 20 cm and a sample width of 20 cm are prepared, and the area S ₁ is measured for each sample piece, and then 100 ° C. in an air oven type heat treatment machine. × Measure the area S ₂ after heat treatment for 15 minutes,
The shrinkage was calculated by the following equation (b), and the average value was defined as the dry heat area shrinkage. Dry heat area shrinkage rate (%) = (S ₁ −S ₂ ) × 100 / S ₁ ... (B) Was evaluated in three steps. ：: There is no filament breakage, and the operability is good. Δ: Filament breakage occurred once per 24 hours and 16 spindles.
×: Filament breakage occurred twice or more per 16 hours of spinning spindles for 24 hours, which is a problem in operation. Smoke emission: The degree of smoke emission at the spinneret during melt spinning was evaluated by visual judgment in the following four stages. ：: Smoke is hardly observed. Δ: Smoking was observed, but no problem occurred in operation. ×: Smoke is extremely large, and smoke is deposited near the spinneret, which is a problem in operation. Stretchability: Stretchability was evaluated in the following three stages based on the incidence of yarn breakage and single filament breakage. ：: Good operability with no breakage of yarn or single filament. △:
One thread break or single filament break occurs every 24 hours. ×: Thread breakage or single filament breakage occurs twice or more per 24 hours, which is a problem in operation.

Example 1 A polypropylene copolymer (Polymer No. 2) having a Q value, a melt flow rate value and a melting point shown in Table 1 and obtained by random copolymerization of propylene and ethylene was prepared by using a usual extruder type. After being melted by a melt extruder, the spinning hole diameter becomes 0.
Using a spinneret having a diameter of 5 mm and a number of holes of 162, melt spinning was performed under the spinning temperature conditions shown in Table 2 with a single hole discharge rate of 1.37 g / min. The fiber was taken out to obtain a highly oriented unstretched long fiber having a single fiber fineness of 3.0 denier. Subsequently, the undrawn filaments were continuously opened by corona discharge without being wound up, and were deposited on a moving conveyor to form a web. Then, using an ultrasonic welding machine equipped with an engraving roll having an adhesion area ratio of 16%, the web was subjected to an adhesive treatment at an ultrasonic frequency of 20 kHz and a processing speed of 5 m / min. To obtain a nonwoven fabric having a basis weight of 40 g / m ² , which was thermally bonded to a nonwoven fabric. Table 2 shows the properties of the obtained long fibers and nonwoven fabric, and the results of the spinnability during melt spinning. This filament has a melt flow rate value of 34 g / 1.
At 0 minutes, as is clear from Table 2, it had a practically sufficient level of elongation and high heat shrinkage. Further, as apparent from Table 2, this nonwoven fabric had a practical nonwoven fabric strength, was excellent in heat shrinkability, and was suitable as a nonwoven fabric for thermoforming.

Example 2 A polypropylene copolymer (Polymer No. 2) was melted in the same manner as in Example 1, and then a single-hole discharge was performed using a spinneret having a spinning hole diameter of 0.4 mm and a hole number of 162. 1.0 g /
It was melt spun under the spinning temperature conditions shown in Table 2 and the spun filament was taken up using a take-up roll having a take-up speed of 600 m / min, and was continuously disposed on the take-up roll and downstream of this roll. The film is stretched with a stretching ratio of 3.0 between the film and a stretching roll (ie, a stretching speed of 1800 m /
Min) and a drawn long fiber having a single fiber fineness of 5.0 denier was obtained. Subsequently, the unstretched filament was continuously passed through an air filter disposed downstream of the stretching roll without being wound, and then opened by corona discharge and deposited on a moving conveyor to form a web. . Next, an adhesive treatment was performed in the same manner as in Example 1 to obtain a nonwoven fabric having a basis weight of 40 g / m ² in which the polypropylene-based long fibers were partially thermally bonded to each other. Table 2 shows the properties of the obtained long fibers and nonwoven fabric, and the results of the spinnability during melt spinning. This long fiber had a melt flow rate value of 34 g / 10 minutes, had a sufficiently high level of elongation for practical use as is clear from Table 2, and had a high heat shrinkage. Further, as apparent from Table 2, this nonwoven fabric has practical nonwoven fabric strength, extremely excellent heat shrinkability, and was suitable as a nonwoven fabric for thermoforming.

Examples 3 to 6 and Comparative Examples 1 to 4 A polypropylene copolymer having a Q value, a melt flow rate value and a melting point shown in Table 1 and obtained by random copolymerization of propylene and ethylene (Example 3) Polymer No. 6 to No. 6
B, C, E, and G, polymer Nos. A, f and h), Q values and melt flow rate values shown in Table 1,
A polypropylene polymer having a melting point (Polymer No. of Comparative Example 4) was melted by an ordinary extruder-type melt extruder, and then a single-hole discharge was performed using a spinneret having a spinning hole diameter of 0.5 mm and a number of holes of 162. The melted fiber was melt-spun at a spinning temperature condition shown in Table 2 at a rate of 1.37 g / min, and the spun filament was taken up using a take-up roll having a take-up speed of 600 m / min. Stretching was performed at a draw ratio of 3.0 with a draw roll disposed on the side (i.e., a drawing speed of 1800 m / min) to obtain a drawn long fiber having a single fiber fineness of 5.0 denier. Subsequently, a web was formed in the same manner as in Example 1, and then subjected to an adhesive treatment in the same manner as in Example 1. The nonwoven fabric having a basis weight of 40 g / m ² in which the polypropylene-based long fibers were partially thermally bonded to each other. I got Table 2 shows the properties of the obtained long fibers and nonwoven fabric, and the results of the spinnability during melt spinning. The long fiber of the embodiment is
The melt flow rate values were 34 g / 10 min, respectively, and as is clear from Table 2, they had a sufficiently high level of elongation for practical use and high heat shrinkage. Further, as apparent from Table 2, the nonwoven fabrics of the examples had practical nonwoven fabric strength, extremely excellent heat shrinkability, and were suitable as nonwoven fabrics for thermoforming. On the other hand, the nonwoven fabric of Comparative Example 1 had a high melt flow rate of long fibers of 87 g / 10 minutes,
That is, since the degree of polymerization of the copolymer was too low, the strength was low, and thus the nonwoven fabric strength was low, reflecting the characteristics of the long fibers. Moreover, since the flowability of the molten polymer was too high, the spinnability and the stretchability were lowered. On the other hand, the nonwoven fabric of Comparative Example 2 had a melt flow rate
g / 10 minutes, that is, the degree of polymerization of the copolymer is too high and the fluidity of the molten polymer is too low, so that the spinnability and drawability are extremely deteriorated, and single fibers are cut during melt spinning. It did not have sufficient quality.
The nonwoven fabric of Comparative Example 3 had low heat shrinkability due to a small amount of ethylene random copolymerized. The nonwoven fabric of Comparative Example 4 had a very low heat shrinkage because it used a normal polypropylene polymer in which ethylene was not randomly copolymerized.

Example 7 A polypropylene copolymer (Polymer No. 2) was melted and spun out in the same manner as in Example 2, and the spun filaments were taken out.
Continuous drawing was performed to obtain a drawn long fiber having a single fiber fineness of 5.0 denier. Subsequently, the drawn filaments were passed through an air filter without being wound up, opened by corona discharge, and deposited on a moving conveyor to form a web. Next, using a hot embossing roll machine equipped with an engraving roll having a bonding area ratio of 17% and a metal roll having a smooth surface, the surface temperature of both rolls was 110 ° C., the linear pressure between both rolls was 50 kg / cm, and the processing speed was high. Was set to 5 m / min, and the web was subjected to an adhesive treatment to obtain a nonwoven fabric having a basis weight of 45 g / m ² in which the polypropylene-based filaments were partially thermally bonded to each other. Table 2 shows the properties of the obtained long fibers and nonwoven fabric, and the results of the spinnability during melt spinning. This long fiber had a melt flow rate value of 34 g / 10 minutes, had a sufficiently high level of elongation for practical use as is clear from Table 2, and had a high heat shrinkage. Further, as apparent from Table 2, this nonwoven fabric had a practical nonwoven fabric strength, was excellent in heat shrinkability, and was suitable as a nonwoven fabric for thermoforming.

Example 8 A polypropylene-based copolymer A (Polymer No. C) having a Q value, a melt flow rate value and a melting point shown in Table 1 and having propylene and ethylene copolymerized at random is shown in Table 1. Polypropylene polymer B (Polymer No. Li) having the indicated Q value, melt flow rate value, and melting point is individually melted by an ordinary extruder-type melt extruder, and then only polymer A is spun. A spinning hole having a hole diameter of 0.5 mm and a number of holes of 108 and a spinning hole diameter of 0.5 mm from which only the polymer B is spun.
Using a mixed fiber spinneret having a spinning hole having 54 holes, the single-hole discharge rate of both polymers was 1.37 g / min (that is, the copolymer weight based on the total weight of the copolymer A and the polymer B). The weight ratio of the polymer A was 66.7%) and the spinning temperature was as shown in Table 2.
The fibers were taken out using an air sucker of m / min to obtain highly oriented undrawn long fibers having a single fiber fineness of 3.0 denier. Subsequently, a web was formed in the same manner as in Example 1 and then subjected to an adhesive treatment in the same manner as in Example 1. The basis weight of the polypropylene filaments partially thermally bonded to each other was 38 g.
/ M ² was obtained. Table 2 shows the properties of the obtained long fiber consisting of only the copolymer A and the long fiber consisting of only the polymer B, the properties of the nonwoven fabric, and the results of the spinnability during melt spinning. As apparent from Table 2, this nonwoven fabric had practical nonwoven fabric strength, excellent heat shrinkability, and was suitable as a nonwoven fabric for thermoforming.

Comparative Example 5 In the same manner as in Example 8, a polypropylene-based copolymer A (Polymer No. C) and a polypropylene-based polymer B (Polymer N)
o. (H) after melting, a spinning hole having a spinning hole diameter of 0.5 mm and a hole number of 80 for spinning only the polymer A and a spinning hole having a spinning hole diameter of 0.5 mm and a hole number of 82 for spinning only the polymer B are formed. (That is, the copolymer A)
The ratio of the weight of the copolymer A to the total weight of the polymer A and the polymer B is 49.4%). Thereafter, the spun filaments are taken out in the same manner as in Example 8, and the single fiber fineness is 3.0 denier. A highly oriented undrawn continuous fiber was obtained. Subsequently, after forming a web in the same manner as in Example 8, an adhesive treatment was performed, and a basis weight in which the polypropylene filaments were partially thermally bonded to each other was 38.
g / m ² of nonwoven fabric was obtained. Table 2 shows the properties of the obtained long fiber consisting of only the copolymer A and the long fiber consisting of only the polymer B, the properties of the nonwoven fabric, and the results of the spinnability during melt spinning.
This nonwoven fabric is inferior in heat shrinkability as apparent from Table 2 due to the low ratio of the weight of the copolymer A to the total weight of the copolymer A and the polymer B, and is unsuitable as a nonwoven fabric for thermoforming. It was something.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

The nonwoven fabric of the present invention is composed of the above-mentioned specific polypropylene long fiber,
It is excellent in shape retention and light weight during thermoforming, and can be suitably used particularly as a thermoforming material such as a container protection filter or a lightweight material.

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Claims (2)

(57) [Claims] [Claim 1] A and 92 wt% or more 97 wt% or less of propylene and 3 wt% or more and 8 wt% of ethylene consists only random copolymer polypropylene-based copolymer has a melt flow rate value is 15 g / 10 minutes or more 80
g / 10 min or less, a single fiber fineness of 10 denier or less, the strength is produced by a spunbond method contains at least 50 wt% as a constituent 2 g / denier or more long fiber
At least the long fibers in the nonwoven fabric are partially thermally bonded to each other at an adhesion area ratio of 3% or more and 50% or less, and have a dry heat area shrinkage ratio at a temperature of 100 ° C. of 1
A polypropylene-based long-fiber nonwoven fabric characterized by being at least 5%. Wherein wherein the Q value of the polypropylene copolymer (weight average molecular weight / number average molecular weight) is 8 or less
2. The polypropylene-based long-fiber nonwoven fabric according to claim 1, wherein