JPH07229052A - Nonwoven manufacturing method - Google Patents

Abstract

PURPOSE:To provide a method for producing a bulky and soft nonwoven fabric excellent in strength, opening property and weave. CONSTITUTION:This method for producing a spun bond nonwoven fabric comprises uniformly combining a polyolefin-based continuous filament A having small heat shrinkage factor with a polyolefin-based or polyester-based continuous filament B having large heat shrinkage factor. In the producing method, a nonwoven fabric having 10-50% difference between the filaments A and B and containing the components A and B at a weight ratio of (35:65) to (65:35) is heat-treated. The resultant nonwoven fabric can especially suitably be used as a raw material for surface materials directly contacting with skin of human body, e.g. sanitary material.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a non-woven fabric obtained by mixing two kinds of continuous filaments having different heat shrinkages. More specifically, the present invention comprises a polyolefin-based or polyester-based continuous filament having a large heat shrinkage and a polyolefin continuous filament having a small heat shrinkage, and a heat-treated nonwoven fabric having strength, openability and The present invention relates to a method for producing a bulky and flexible non-woven fabric which is excellent in formation and can be suitably used as a surface material for sanitary materials such as disposable diapers and sanitary napkins.

[0002]

2. Description of the Related Art Spunbonded non-woven fabrics having continuous long fibers as constituent fibers have high strength and are relatively inexpensive as compared with short fiber non-woven fabrics having short fibers as constituent fibers, and thus are used in various applications. There is. However, spunbonded nonwoven fabrics composed of continuous long fibers are generally inferior in bulkiness and flexibility as compared with short fiber nonwoven fabrics having crimps.

For this reason, in a spunbonded non-woven fabric composed of continuous long fibers, one of the long fibers is formed when a high molecular polymer is melt-spun from a spinneret having irregularly shaped spinning holes and then stretched and solidified by a high-speed air stream. A method for producing a spunbonded nonwoven fabric has been proposed in which the filaments are crimped by cooling only the side faces thereof and then the filaments are laminated (Japanese Patent Laid-Open No. 1-148862).

The spunbonded non-woven fabric obtained by this method is bulky and flexible, but has the drawback that the crimped long fibers adjacent to each other are entangled with each other at the time of opening, and the formation becomes inhomogeneous due to poor opening. This tendency is remarkable especially in thin products having a small basis weight.

Further, even with the latent crimpable filaments, it is unavoidable that a certain degree of crimp is manifested, so that the crimpable filaments have a drawback of poor opening. In order to make up for this drawback, a method has been proposed in which side-by-side type or eccentric core-sheath type composite filaments having crimps and non-composite filaments composed of a single component are mixed (Japanese Patent Laid-Open No. Hei 10 (1999) -135242) 5-195
No. 406). By this method, the openability of the crimped composite long fibers is improved, and a nonwoven fabric having a uniform texture is obtained.

However, even in this method, if the ratio of the crimped filaments which has become actualized is increased, the texture is deteriorated,
The smaller the size, the better the texture, but the bulkiness is inferior. Such a defect becomes remarkable especially in a thin product having a small basis weight. As described above, both the texture and the bulkiness are trade-offs, and it is extremely difficult to satisfy both of them at the same time.

[0007]

In view of the above situation, the present inventors have attempted to achieve both openness and bulkiness of continuous long fibers, and therefore have good openability at the time of opening and have high bulkiness after web formation. As a result of earnestly repeating research on expressing, two kinds of continuous long fibers having different heat shrinkage rates are opened and mixed by a usual method, and after forming a web, a fused area is provided with an interval, When this was heat-treated, it was found that long fibers having a small heat shrinkage ratio form loops, thereby exhibiting the same bulkiness as crimpable long fibers, and the present invention has been completed.

It is an object of the present invention to provide a method for producing a spunbonded nonwoven fabric which is excellent in strength, has a homogeneous texture, and is bulky.

[0009]

According to the present invention, a spunbonded non-woven fabric is obtained by uniformly mixing a polyolefin continuous filament A having a small heat shrinkage and a polyolefin or polyester continuous filament B having a large heat shrinkage. In the manufacturing method of, the difference in heat shrinkage between the continuous filaments A and B is 10 to 5
0%, and A: B is 35:65 to 65: by weight.
The method for producing a spunbonded nonwoven fabric is characterized in that the nonwoven fabric made of 35 is heat-treated.

The non-woven fabric according to the present invention is obtained by mixing and depositing continuous filaments having different heat shrinkage rates to form a web, thermocompression-bonding, and further heat-treating. For the web formation, a known spunbond method can be applied as it is. Since the continuous continuous fiber used in the present invention is a non-crimpable fiber made of a polyolefin-based or polyester-based single-component resin, it has good openability and a web with a homogeneous texture can be obtained. Further, the web thermocompression bonded as described above may be provided between a heated embossing roll and a smooth roll having a large number of convex portions so that the fusion-bonded areas are arranged at intervals on the surface thereof, or a large number of them. It is formed by introducing it between a pair of heated embossing rolls having convex portions.

In the fused area provided on the surface of the non-woven fabric in this manner, continuous long fibers are bonded by thermal fusion, and the area of the fused area is within the range of 4 to 10% of the area of the spunbonded non-woven fabric. is there. If the area of the fusion bonding area is less than 4%, the strength of the nonwoven fabric is insufficient, and if it exceeds 10%, the resulting nonwoven fabric lacks bulkiness and flexibility, which is not suitable.

The non-woven fabric provided with the fusion-bonding area as described above is further subjected to heat treatment with hot air at a combination of a temperature of 110 to 140 ° C. and a time of 1 to 5 minutes. As a result of this heat treatment, the long fibers having a high heat shrinkage shrink more than the long fibers having a low heat shrinkage, and as a result, the fusion zones are connected at the shortest by the long fibers having a high heat shrinkage. Long fibers having a low shrinkage rate form loops between the fused areas, which imparts bulk to the nonwoven fabric.

The fineness of the continuous long fibers used for imparting the bulkiness in the present invention is 1 to 5 denier. When the fineness is more than 5 denier, the flexibility of the nonwoven fabric is lowered, and it becomes difficult to use it for applications such as a surface material for sanitary materials. When the fineness is less than 1 denier, the manufacturing conditions are strict and both are not suitable. Further, the thermal shrinkage of the continuous fiber varies depending on the type of resin, the degree of polymerization, the spinning speed (stretching degree), etc., but the polyolefin continuous continuous fiber A having a small thermal shrinkage used in the present invention is used. As the resin forming
Examples thereof include polypropylene having a heat shrinkage of 5 to 10%, a random copolymer of ethylene-propylene, a blend structure of polyethylene and polypropylene, and the like, which is mainly composed of polypropylene and has a slightly higher heat shrinkage. As the resin forming the polyolefin-based or polyester-based continuous filament B having a large heat shrinkage, for example, polyethylene having a heat shrinkage of 20 to 40%, 40 to 6
0% polyethylene terephthalate, a blended structure of polyethylene and polypropylene, and the like,
In the present invention, the difference in heat shrinkage between two kinds of resins appropriately selected from these is 10 to 50%, preferably 15
~ 40% is used.

When the difference in the heat shrinkage ratio is less than 10%, the bulkiness effect is weakened because the loop formation by the long fibers having the small heat shrinkage ratio is small. In contrast, the difference in heat shrinkage is 50
If it is larger than 0.1%, the formation of the loop becomes large, the touch feeling is inferior, and the versatility of the resin used for such resin combination is deteriorated, which is not suitable.

The weight ratio of the polyolefin continuous filament A having a small heat shrinkage to the polyolefin or polyester continuous filament B having a large heat shrinkage is 35: 6 for A: B.
5 to 65:35. When the ratio of the polyolefin continuous filaments A having a small heat shrinkage ratio is less than 35, the strength is excellent, but the bulkiness cannot be imparted to the nonwoven fabric, and when the ratio exceeds 65, the bulkiness is excellent but the strength is reduced. Not suitable as it does.

As described above, the nonwoven fabric according to the present invention is formed by mixing and depositing continuous filaments having different heat shrinkage ratios, and then thermocompression-bonding the melted area on the web to form the nonwoven fabric. It can be obtained by further heat treatment. The web is formed by the well-known spunbond method. Since each continuous long fiber is a non-crimpable fiber made of a polyolefin-based or polyester-based single-component resin, the openability is good and the formation is uniform. . Further, each fusion-bonded area formed by thermocompression bonding after forming the web is arranged with an interval, and a long fiber having a large heat shrinkage is provided between the fusion-bonded areas due to the subsequent heat treatment. The longest fibers that are connected at the shortest, while having a low heat shrinkage, form loops between these fused areas,
This gives the nonwoven fabric bulkiness. Therefore, the method for producing a non-woven fabric of the present invention provides a non-woven fabric which can be particularly preferably used as a material for a surface material of a sanitary material that comes into direct contact with the skin of the body.

[0017]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1 A polypropylene resin having a melt flow rate of 40 and a polyethylene resin having a melt flow rate of 20 were heated to a temperature of 230 ° C. to be melted, and then discharged from different discharge holes in the same die, and melted by a known method. Continuous long fibers were obtained by the spinning method. Immediately after this, this long fiber was drawn into a long fiber having a fineness of 2 denier, which was collected on a collecting conveyor and the basis weight was 23 g / m ^2.
Got the web. The weight ratio of polypropylene long fibers to polyethylene long fibers was 63:37. This web,
It was introduced between a heated embossing roll having a large number of dot-shaped protrusions and a smooth roll to obtain a non-woven fabric having spot-shaped fused regions. Next, this non-woven fabric was introduced into a hot air circulation type dryer and subjected to heat treatment in a relaxed state at a hot air temperature of 120 ° C. for 1 minute. Polypropylene filaments were obtained by collecting each filament of the same denier that was discharged from the outlet of the die and stretched under the same conditions as in the case of manufacturing a nonwoven fabric as described above and measuring the heat shrinkage ratio. 7%, polyethylene long fiber 22%, the difference in heat shrinkage was 15%. The area of the fused area was 5% with respect to the area of the nonwoven fabric. The density and tensile strength of the obtained nonwoven fabric were measured.

The test method used in the present invention is as follows. (1) Thermal contraction rate A sample with a length of 50 cm was sampled and 100 m per 1 denier.
Obtain the sample length L0 when a load of g is applied, then remove the load, put the sample in boiling water, treat it for 3 minutes, and then apply a load of 100 mg per denier to the sample again. L1 was obtained, and the heat shrinkage rate (boiling water shrinkage rate) was calculated by the equation (1). Thermal shrinkage (%) = {(L0-L1) / L0} × 100 ... (1)

(2) Thickness Compression tester manufactured by Kato Tech Co., Ltd. (model: KES-
Using FB3), measure 0.5 cm for a measuring area of 2 cm ² of the non-woven fabric.
A load of g / cm ² was applied and the thickness D (mm) at that time was measured. (3) Apparent Density The above-mentioned thickness Dmm was determined, and when the basis weight of the nonwoven fabric having this thickness was Mg / m ² , the apparent density was calculated by the formula (2). Apparent density (g / cm ³ ) = M / (D × 1000) (2)

(4) Tensile strength Using a Tensilon universal tensile tester (model: PTM-100) manufactured by Tohoku Seimitsu Co., Ltd., a tensile speed of 300 mm /
A tensile test was conducted with a sample length of 80 mm and a sample width of 100 mm, and the measured breaking strength was multiplied by 3, and the tensile strength per 300 mm width was shown.

Example 2 An ethylene-propylene random copolymer having a melt flow rate of 30 (heat shrinkage of 18%) and a polyethylene resin having a melt flow rate of 18 (heat shrinkage of 30%) were used.
Example 1 except that the area of the fused area of the nonwoven fabric was 8%
A bulky non-woven fabric was produced in the same manner as above, and the density and tensile strength were measured. The difference in heat shrinkage between the two continuous filaments is 12
%Met.

Example 3 Similar to Example 1 except that a polyethylene terephthalate resin having an intrinsic viscosity η = 0.65 (heat shrinkage of 47%) and a polypropylene resin having a melt flow rate of 40 (heat shrinkage of 7%) were used. A bulky non-woven fabric was produced and the density and tensile strength were measured. The difference in heat shrinkage between the two continuous filaments was 40%.

Example 4 A bulky nonwoven fabric was produced in the same manner as in Example 1 except that the weight ratio of continuous polypropylene continuous fibers to continuous polyethylene continuous fibers was 40:60, and the density and tensile strength were measured.

Comparative Example 1 Example 1 except that an ethylene-propylene random copolymer having a melt flow rate of 25 (heat shrinkage of 22%) and a polyethylene resin having a melt flow rate of 18 (heat shrinkage of 30%) were used. A non-woven fabric was produced in the same manner as above, and the density and tensile strength were measured. The difference in heat shrinkage between the two continuous filaments was 8%.

Comparative Example 2 A nonwoven fabric was produced in the same manner as in Example 1 except that the weight ratio of polypropylene continuous filaments to polyethylene continuous filaments was 30:70, and the density and tensile strength were measured.

Comparative Example 3 A nonwoven fabric was produced in the same manner as in Example 1 except that the weight ratio of polypropylene continuous filaments to polyethylene continuous filaments was 70:30, and the density and tensile strength were measured.

The measurement results obtained in Examples and Comparative Examples are shown in Table 1.

[0029]

[Table 1]

As is clear from Table 1, the non-woven fabric according to the present invention has a high strength and an excellent openability, and thus has a good texture, and when compared with the same basis weight, the thickness is extremely large, the apparent density is small, and the bulkiness is high. Excellent (Examples 1 to 1
4). On the other hand, when the difference in thermal shrinkage between the two types of continuous filaments is less than 10%, the formation of loops is small and the apparent density is large and the bulkiness is poor (Comparative Example 1). When the ratio of the long fibers having a large heat shrinkage is large, the strength is excellent, but the bulkiness is poor (Comparative Example 2). Conversely, when the ratio of the long fibers having a large heat shrinkage is small, the bulkiness is excellent, They are not suitable because they are inferior in strength (Comparative Example 3).

[0031]

EFFECTS OF THE INVENTION Since the present invention has the constitution as described above, it has excellent strength and excellent openability, so that even a thin article having a low basis weight can obtain a homogeneous texture, and is bulky and flexible spunbond. The effect of providing a manufacturing method of a nonwoven fabric is produced.

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Claims (1)

[Claims] 1. A method for producing a spunbonded non-woven fabric, comprising a continuous polyolefin fiber A having a low heat shrinkage and a continuous polyolefin fiber or a polyester continuous fiber B having a high heat shrinkage, which are uniformly mixed. Manufacture of a spunbonded nonwoven fabric, characterized in that the difference in the heat shrinkage ratio between the fibers A and B is 10 to 50% and the weight ratio of A: B is 35:65 to 65:35. Method.