JPH08158226A - Bulky nonwoven fabric and its production - Google Patents

Abstract

PURPOSE: To obtain a flexible and bulky nonwoven fabric having much crease- like unevenness not causing shape deformation on the surface and useful as a filter, etc., by laminating an unshrinkable fiber layer onto the both sides of a highly shrinkable fiber layer and carrying out high pressure water flow treatment of these layers, followed by heat treatment of the layer. CONSTITUTION: Fiber layers comprising a fiber which does substantially not shrink at a temperature at which a highly shrinkable fiber contracts are laminated to the both sides of a fiber containing >=50wt.% of the highly shrinkable fiber whose maximum shrinkage factor by heating is at least 50% and these layers are entangled and integrated and then, the highly shrinkable fiber layer is thermally shrunk by heat treatment. Thereby, many ridge-like protruded parts 2 are formed and filtering area can be increased without pleating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bulky nonwoven fabric having a large number of wrinkles formed on its surface, which can be effectively used as a filter, a mask, a wiper or a towel. is there.

[0002]

2. Description of the Related Art Heretofore, various bulky nonwoven fabrics having an increased apparent thickness of the nonwoven fabric have been proposed. For example, in JP-A-2-160962, as a nonwoven fabric suitable for wipers and bandages, a bulky nonwoven fabric in which a crepe is formed on the surface by utilizing the shrinkability of elastic fibers such as highly spirally crimped fibers and elastomer fibers Is proposed. Further, in JP-A-62-141167, a heat-shrinkable sheet and a non-heat-shrinkable sheet are partially bonded and integrated, and then heat-treated to form a convex portion between the bonding portion and the bonding portion. A bulky nonwoven fabric has been proposed. Furthermore, JP-A 1-2
Japanese Patent No. 01569 proposes a bulky reinforced nonwoven fabric comprising a web containing heat-fusible fibers and a monofilament having a large heat shrinkage, and wrinkles formed on the surface by utilizing the shrinkage force of the monofilament.

The larger the filtration surface of the filter, the more
Since it can be subjected to filtration for a longer period of time, efforts are being made to increase the filter surface by pleating a flat filter.

Highly shrinkable fibers are disclosed in Japanese Patent Laid-Open No. 60-27.
The polyvinyl alcohol fiber using the water-swelling action described in Japanese Patent Application Laid-Open No. 09 is put to practical use, and is also disclosed in JP-A-58.
There is an example of a polyolefin-based heat-shrinkable fiber using an α-olefin having a carbon number of butene or more and a propylene copolymer having a propylene content of 50 to 85 mol%, which utilizes the heat-shrinkage property described in JP-A-214550. Furthermore, examples of the heat-shrinkable fibers having a maximum shrinkage of 50% or more include fibers of an ethylene-propylene random copolymer and an ethylene-propylene-butene-1 terpolymer previously proposed by the present applicant. (JP-A-5-44108
(See issue)

[0005]

Generally, not only household wipers but also wipers for large wiping amount have a large number of irregularities on the surface, and the wiped portions are pushed into the recesses, and the wiper surface is not covered. Ideally, it should be kept clean so that it does not leave too much residue. Therefore, it can be said that a bulky nonwoven fabric, which has many wrinkle-like irregularities formed on the surface thereof and is not easily flattened by tension or the like, is most preferable as the wiper.

However, the bulky non-woven fabric proposed in the above-mentioned Japanese Patent Laid-Open No. 2-160962 is suitable for scratches, bandages, cushion covers, etc. because it exhibits elasticity by heating. When used as a wiper or towel, there is a problem that the crepe easily stretches. In addition, the surface of the bulky nonwoven fabric described in JP-A-62-141167 is in a state in which the nonwoven fabric is swollen between the bonding portions rather than forming the convex portions. Such a "bulge" is
When surface pressure is applied, it is easy to flatten. In addition, JP-A-1-
It cannot be denied that the non-woven fabric proposed in 201599 lacks flexibility because the monofilament having a relatively large fineness remains inside as a core material.

That is, the conventional bulky nonwoven fabric is not satisfactory in terms of morphological stability and flexibility of the uneven portion, and a flexible nonwoven fabric having a large number of wrinkle-like unevenness that does not lose its shape is used in the industry. Was strongly requested in.

Similarly, in the field of filters, it is desired to realize a filter having a large filtering area without pleating, that is, a nonwoven fabric having a large number of irregularities formed on its surface.

On the other hand, Japanese Patent Application Laid-Open No. 58-214550 and Japanese Patent Application Laid-Open No. 5-44108 teach only examples of yarns and woven / knitted fabrics obtained by the yarns as the use of heat-shrinkable fibers. . This is because it is unlikely that the fibrous web containing these highly shrinkable fibers will have a uniform shrinkage due to the heat treatment since the heat shrinkage initiation temperature is relatively low and the shrinkage rate is large. That is, at the time of filing the invention, the idea of using the highly shrinkable fibers as a part of the constituent fibers of the non-woven fabric to form a large number of wrinkle-shaped irregularities on the surface of the non-woven fabric was unexpected.

In view of these circumstances, the present inventors have conducted studies to obtain a bulky nonwoven fabric which is flexible and has a large number of wrinkle-like fine irregularities formed on the surface thereof. By laminating a fiber layer composed of non-shrinkable fibers on both sides of the fiber layer containing the, and entangled between the fibers of both fiber layers, by heat treatment, fine wrinkle-like unevenness on the front and back of the nonwoven fabric The inventors have found what can be done and have reached the present invention.

[0011]

That is, according to the present invention, the high shrinkable fibers are provided on both sides of a first fiber layer containing 50% by weight or more of highly shrinkable fibers having a maximum heat shrinkage of at least 50% by heating. In a nonwoven fabric in which a second fiber layer composed of fibers that do not substantially heat shrink at the shrinking temperature is located and both fiber layers are integrated by inter-fiber entanglement, a large number of second fiber layers are formed in the second fiber layer due to heat shrinkage of the first fiber layer. The present invention relates to a bulky nonwoven fabric having wrinkle-shaped irregularities. The contents will be described below.

The highly shrinkable fibers used in the present invention are fibers having a maximum heat shrinkage of at least 50%. Here, the maximum heat shrinkage ratio means the maximum shrinkage ratio in a shrinking state in which the heated fiber maintains the fiber shape. 50% heat shrinkage
This is because if it is less than 1, the bulkiness of the first fibrous layer is insufficient and a bulky nonwoven fabric having a large number of wrinkle-like fine irregularities formed cannot be obtained.

Further, the first fiber layer must contain 50% by weight or more of such highly shrinkable fibers. 50% by weight
If it is less than 1, the shrinkage of the entire first fiber layer is insufficient and it becomes impossible to form irregularities on the second fiber layer.

As a fiber having a maximum heat shrinkage of 50% or more,
A fiber made of a polymer containing an ethylene-propylene random copolymer having a melting peak temperature (Tm ° C.) of 130 <Tm <145 can be mentioned. Here, the melting peak temperature means the temperature at which the DSC curve shows the maximum value when the heat of fusion of the polymer is measured by a differential scanning calorimeter (DSC). If the melting peak temperature is less than 130 ° C., the polymer exhibits rubber-like elasticity and the card passability of the fiber deteriorates. If the melting peak temperature exceeds 145 ° C., the dry heat shrinkability of the fiber becomes about that of a normal polypropylene fiber. It is not desirable because it will end up. Further, it is desirable that the ethylene-propylene random copolymer is contained in an amount of 70% by weight or more. 7
This is because if it is less than 0% by weight, the maximum heat shrinkage rate of the fiber will be less than 50%.

A fiber made of only an ethylene-propylene random copolymer and stretched about 3 times has a fiber just below the melting point.
It exhibits a heat shrinkage of about 93% within 1 minute at 35 ° C. Therefore, another polymer may be mixed in order to control the heat shrinkability. As the polymer to be mixed, ethylene-butene-1-
A propylene terpolymer is preferred. You may mix polyolefin polymers, such as polypropylene.

Since fibers for nonwoven fabrics are generally manufactured by adhering an aqueous solution of a fiber treatment agent such as an antistatic agent and drying the fibers,
Highly shrinkable fibers having a shrinkage initiation temperature of more than 100 ° C. may be used. Further, since shrinkage stress is remarkably reduced when the fiber is melted, it is necessary to consider the time of heat shrink processing so that the fiber is not completely melted. For example, as the highly shrinkable fiber, the above-mentioned melting peak temperature (Tm ° C)
When a fiber made of a polymer containing an ethylene-propylene random copolymer of 130 <Tm <145 is used, the heat shrinkage processing temperature (T ° C.) is 100 <T ≦ Tm + 30.
It is recommended to set so that

The mode of the first fiber layer is not particularly limited, and a parallel web made of staple fibers, a cross web, a semi-random web, a random web, or a spunbonded nonwoven fabric in which continuous fibers are accumulated can be arbitrarily used. In particular, when using a web in which the fibers are arranged in one direction such as a parallel web, the shrinkage proceeds in one direction, so that unevenness is likely to be uniformly formed in the second fiber layer,
A non-woven fabric having an orderly appearance can be obtained.

The fibers constituting the second fiber layer located on both sides of the first fiber layer are capable of forming a fiber aggregate and do not substantially shrink at the temperature at which the highly shrinkable fiber shrinks. The material is not particularly limited. For example, regenerated fibers such as rayon, semi-synthetic fibers such as acetate, natural fibers such as cotton and wool, synthetic fibers such as polypropylene, polyethylene, polyester, nylon, vinyl chloride, vinylon, etc. One or two or more can be selected and used. Also, the fiber shape and the like are not limited, and split-type composite fibers, fibers having an irregular cross section, and the like can be arbitrarily used.

For example, when the bulky nonwoven fabric of the present invention is used for a wet wiper or the like, it is preferable that the second fiber layer is composed of hydrophilic fibers such as rayon. When used as a precision wiper, the second fiber layer may be composed of a splittable conjugate fiber made of a combination of nylon / polyester or polyester / polypropylene or an easily fibrillated acrylic fiber. And when used for filters and masks,
It is convenient to mix the above-mentioned splittable conjugate fiber or easily fibrillated acrylic fiber with ordinary fiber to form the second fiber layer.

In consideration of the ease of interfiber entanglement with the first fiber layer, the second fiber layer is most preferably a web or nonwoven fabric composed of staple fibers. If interfiber entanglement with the first fiber layer is possible, spunbonded non-woven fabrics, melt blown non-woven fabrics, tow open webs, and other long fiber aggregates or woven or knitted fabrics can be used.

Of course, it is also possible to place two fiber layers of different materials and modes on the front and back surfaces of the first fiber layer. For example, when one of the second fiber layers is composed of rayon and the other is composed of polypropylene, and the nonwoven fabric of the present invention is composed by laminating it on the surface and the back surface of the first fiber layer, respectively, the surface is rich in hydrophilicity and the back surface is It is possible to obtain a non-woven fabric having the two properties of being highly hydrophobic.

The basis weight of the first fiber layer and the second fiber layer may be determined according to the application of the non-woven fabric, but it should be noted that the basis weight after heat treatment increases depending on the degree of shrinkage of the first fiber layer. There is a need. Considering easiness of entanglement between fibers of both fiber layers and uniformity of formation of irregularities, the basis weight before heat treatment of both fiber layers is preferably 250 g / m ² or less. More preferably 25 to 150 g / m ^2, i.e. 5 to 30 g / m ² of the first fiber layer, 10 to 60 g of the second fiber layer
/ M ² is recommended. Further, when the basis weight of one of the second fiber layers is made smaller than that of the other second fiber layer, it is possible to obtain a nonwoven fabric having irregularities of different sizes formed on the front and back sides.

Next, the method for producing the bulky nonwoven fabric of the present invention will be described.

The bulky nonwoven fabric of the present invention is characterized in that a large number of wrinkle-like irregularities are formed in the second fiber layer by heat shrinkage of the first fiber layer, and as a result, the thickness is increased. In order for such wrinkle-like irregularities to be uniformly formed in the second fiber layer, the constituent fibers of both fiber layers are mixed into each other before the first fiber layer undergoes heat shrinkage, and It is essential that are entangled. Further, when a fiber such as a parallel web in which constituent fibers are not substantially entangled is used as the fiber layer, it is necessary to entangle the fibers before heat treatment.

As a method of interlacing the fibers of both fiber layers,
A method using high-pressure water stream treatment can be mentioned. In particular,
The combined weight of both fiber layers before heat treatment is 15 to 100 g /
A method of high-pressure water flow treatment is preferable for those of about m ² . In this case, if the treatment is performed without increasing the water pressure so much, the unevenness can be formed uniformly. Further, interlacing between fibers by needle punching is also possible. In particular, the unit weight of both fiber layers before heat treatment is 100 to 30
For about 0 g / m ^2, needle punching is preferable.

After the fibers of both fiber layers are entangled with each other, heat treatment is performed to shrink the first fiber layer and form wrinkle-like irregularities in the second fiber layer. The heat treatment is performed at a temperature at which the highly shrinkable fibers in the first fiber layer shrink. At this time, it is desirable that the load is not applied to the object to be treated as much as possible.

The wrinkle-shaped uneven projections are formed by peeling off a part of the second fiber layer from the first fiber layer and causing the peeled portion to become an excess portion due to surface shrinkage of the first fiber layer. To be done. Therefore, in the concave portion, the fibers of both fiber layers are still entangled, and the existence of the entangled portion ensures the integrity of the both.

A change in the thickness of the nonwoven fabric after the heat treatment can be mentioned as a measure of the size of the irregularities formed on the second fiber layer. In other words, when the area shrinkage ratio of the first fiber layer is constant, the smaller the change in thickness after heat treatment, the larger the number of fine protrusions formed. In the bulky nonwoven fabric of the present invention, the area shrinkage ratio of the first fiber layer is about 40 to 85.
%, That is, the area after heat treatment is 40 to 15% before heat treatment, the thickness of the nonwoven fabric after heat treatment is 2 to 6.5 times the thickness of the nonwoven fabric before heat treatment. Is desirable. If it is less than 2 times, the formed convex portions are too fine to be practical, and if it exceeds 6.5 times, the convex portions become large and the number thereof becomes small.

[0029]

In the present invention, the first fiber layer containing the highly shrinkable fibers is significantly shrunk by heat treatment, so that many wrinkle-like irregularities are formed in the second fiber layer.

Since the second fiber layer itself exhibits almost no heat shrinkability, when the first fiber layer shrinks, an excess area is produced.
And this surplus area will form a convex part. That is, the second fiber layer is a layer in which wrinkle-like irregularities are exclusively developed,
It directly contributes to the increase in bulk of the nonwoven fabric. Also,
Various properties can be imparted to the non-woven fabric by appropriately selecting the material of the constituent fibers.

In the present invention, since the first fiber layer is heat-shrinked after the fibers of both fiber layers are previously entangled by high-pressure water flow treatment or the like, fine wrinkle-like irregularities are uniformly formed on the second fiber layer. To be done. Since the unevenness is formed by an irreversible action and is fixed, it is not easily deformed and is not flattened even when tension or the like is applied.

[0032]

EXAMPLES The present invention will be described below with reference to examples.

[Production of highly shrinkable fiber] The melting point is 140 ° C.,
An ethylene-propylene random copolymer having a melt flow rate value (230 ° C.) of 15 g / 10 min was spun at a spinning temperature of 260.
It was melt spun at ℃. Then, this was stretched 3.6 times in hot water at 90 ° C., and while the fiber treatment agent was applied, mechanical crimping of 16 pieces / inch was performed in a stuffing box,
After being dried in a hot-air penetrating dryer at 0 ° C. for 15 minutes, the staple fiber was cut to obtain 2 denier and 51 mm staple fiber.
Bundling 100 fibers, 130 ℃, 140 ℃,
The heat shrinkage rates when exposed to each temperature of 150 ° C. were 35%, 62%, and 83%, respectively.

Example 1 A parallel web having a basis weight of 10 g / m ² was prepared with a parallel card using only the above-mentioned highly shrinkable fibers, and this was used as the first fiber layer. Also, fineness 2
A denier rayon fiber having a fiber length of 51 mm was used to prepare a parallel web having a basis weight of 20 g / m ² with a parallel card, and this was used as a second fiber layer.

Then, a second fiber layer is laminated on both sides of the first fiber layer to form a laminated web having a basis weight of 70 g / m ² , and then a water pressure of 30 kg is obtained from a nozzle provided with orifices having a hole diameter of 0.1 mm at intervals of 1 mm. A high-pressure columnar water flow of / cm ² was jetted to entangle the constituent fibers in each fiber layer and the constituent fibers of both fiber layers. Then, heat treatment was performed for about 30 seconds in the hot air penetrating type processing machine at the temperature shown in the table to shrink the first fiber layer to obtain a bulky nonwoven fabric. The surface condition is shown in Figure 1.
Shown in Thus, the length of the non-woven fabric (1) is 5 to
A ridge-shaped convex portion (2) having a width of 20 mm and a width of 1 to 3 mm is formed in a direction (transverse direction) that forms an angle of 90 ° with the fiber direction in the fiber web, and they are arranged substantially parallel to each other. The appearance was such that the fine wrinkles of the were added orderly. Table 1 shows the physical properties of this nonwoven fabric.

[0036]

[Table 1]

[Example 2] As the second fiber layer, 70% by weight of polypropylene fiber (2 denier, 51 mm) and 30% by weight of core-sheath type composite fiber (1.5 denier) whose core component / sheath component is polypropylene / polyethylene. , 38 mm) were mixed to prepare a parallel web having a basis weight of 20 g / m ² , which was laminated on both sides of the same first fiber layer as used in Example 1. Then, a bulky nonwoven fabric was prepared in the same manner as in Example 1. This bulky non-woven fabric is the same as in Example 1,
A large number of ridge-shaped projections were formed on the surface, and it had a regular appearance. Table 2 shows the physical properties of this non-woven fabric.

[0038]

[Table 2]

Comparative Example 1 30% by weight of the above-mentioned highly shrinkable fiber and 70% by weight of rayon fiber used in Example 1 were mixed to prepare a parallel web having a basis weight of 10 g / m ² with a parallel card. Was used as the first fiber layer. Then, a parallel web having a basis weight of 20 g / m ² made of rayon fibers used in Example 1 was prepared as the second fiber layer and laminated on both surfaces of the first fiber layer. This was subjected to a high-pressure water stream treatment in the same manner as in Example 1 and then heat-treated for about 30 seconds in a hot-air penetration type processing machine at the temperature shown in the table, and no irregularities were formed in the second fiber layer. . Table 3 shows the physical properties of the obtained nonwoven fabric.

[0040]

[Table 3]

In Tables 1 to 3, the physical properties of the nonwoven fabric were evaluated according to the following methods.

[Thickness] Thickness measuring machine (Product name: THICKNES
S GAUGE model CR-60A (manufactured by Daiei Chemical Seiki Co., Ltd.)
Was measured with a load of 3 g per cm ² applied to the sample.

[Change in thickness] (thickness of nonwoven fabric after heat treatment / thickness of nonwoven fabric before heat treatment)

[Area Shrinkage Ratio] A 20 cm × 20 cm square frame is placed on the surface of the non-woven fabric before heat treatment, and a mark is applied at a position corresponding to the midpoint (4) of each side of the square (3) as shown in FIG. Turn on. And after heat treatment, the midpoint (4) facing each other
The areas of the rectangle (5) are considered as if the squares became a rectangle (5) with the sides of the vertical (6) and the sides of the horizontal (7) as a result of heat shrinkage. It was calculated.
From this result, the area shrinkage rate was calculated by the following equation.

[0045]

[Equation 1]

[Tensile strength, breaking length, elongation] JIS L
According to 1096, a sample piece having a width of 5 cm and a length of 15 cm is grasped at a gripping interval of 10 cm, and stretched at a pulling rate of 30 cm / min using a constant-speed extension type tensile tester to measure the load value and the extension rate at the time of cutting. Tensile strength and elongation. The breaking length is the breaking length (km) = tensile strength (kg / 0.05m) / [sample width (m) x
Basis weight (g / m ² )].

[0047]

As described above, the nonwoven fabric of the present invention has the second fiber layer made of fibers which do not substantially shrink on both sides of the first fiber layer containing the highly shrinkable fiber, and has a fine fiber on both sides. It is a bulky non-woven fabric having a large number of wrinkle-shaped irregularities.
Since the irregularities are formed by an irreversible action, they are not easily deformed and are not flattened by tension or the like. In addition, a flexible nonwoven fabric can be obtained by forming the first fiber layer containing the highly shrinkable fiber as a fiber web having a low basis weight and entangled and integrating the first fiber layer and the second fiber layer by high-pressure water flow treatment.

Therefore, when this bulky nonwoven fabric is used as a wiper, both sides can be used as a wiping surface without waste, and since the unevenness is less likely to collapse, the excellent wiping effect lasts for a long time and is economical. And because it is flexible, it does not feel uncomfortable to handle with hand and is easy to use. When this bulky nonwoven fabric is used as a filter, the surface area is large, so that the filtration life can be improved. In addition to this, it can be applied to a heat insulating material such as clothes, a packaging material utilizing the design effect of the unevenness of the surface, and an interior inner layer material.

[Brief description of drawings]

FIG. 1 is a plan view showing an example of a bulky nonwoven fabric of the present invention.

FIG. 2 is a schematic diagram showing an area shrinkage evaluation method.

[Explanation of symbols]

 1 Bulky nonwoven fabric 2 Ridge-shaped protrusions

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location D01F 6/30

Claims (4)

[Claims] 1. The maximum heat shrinkage ratio by heating is at least 5.
On both sides of the first fiber layer containing 50% by weight or more of highly shrinkable fibers of 0%, a second fiber layer composed of fibers that do not substantially shrink at the temperature at which the highly shrinkable fibers shrink is located. A bulky nonwoven fabric in which a number of wrinkle-shaped irregularities are formed in the second fiber layer by heat shrinkage of the first fiber layer in the nonwoven fabric in which the layers are integrated by inter-fiber entanglement. 2. The area shrinkage ratio of the first fiber layer after heat shrinkage is 4
The thickness of the nonwoven fabric after heat shrinkage is 0 to 85%, which is 2.5 to 6 times the thickness of the nonwoven fabric before heat shrinkage.
The bulky nonwoven fabric described. 3. The high shrinkable fiber has a melting peak temperature (Tm).
The bulky nonwoven fabric according to claim 1 or 2, which is a fiber made of a polymer containing 70% by weight or more of an ethylene-propylene random copolymer having a C) of 130 <Tm <145. 4. The maximum heat shrinkage ratio by heating is at least 5.
On both sides of the first fiber layer containing 50% by weight or more of 0% highly shrinkable fiber, a second fiber layer made of fibers that do not substantially shrink at the temperature at which the highly shrinkable fiber shrinks is laminated. After the high-pressure water stream treatment is performed, the constituent fibers of the first fiber layer and the second fiber layer are entangled and integrated, and then a heat treatment is performed to cause the first fiber layer to heat-shrink, resulting in a large number of wrinkles in the second fiber layer. A method for producing a bulky non-woven fabric, which comprises forming irregularities in a shape.