JPH11117165A - Elastic melt blow nonwoven fabric - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a nonwoven fabric comprising an ultrafine yarn having improved elasticity, excellent melt blow characteristics and antiblocking properties in an elastic melt blow nonwoven fabric using a low-density polyethylene. SOLUTION: This elastic melt blow nonwoven fabric comprises a composition composed of (A) 70-90 wt.% of a low-density polyethylene having 0.860-0.920 density, (B) 5-10 wt.% of a polypropylene and (C) 5-20 wt.% of a styrene-based elastomer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a stretchable melt-blown nonwoven fabric, and more particularly to a stretchable meltblown nonwoven fabric made of a polyolefin-based thermoplastic elastomer.

[0002]

2. Description of the Related Art A technique for producing a nonwoven fabric made of ultrafine fibers by a melt blow method is already known in many patents and literatures. In addition, elastic melt-blown nonwoven fabrics provided with elasticity are used for applications such as sanitary materials, diaper materials, and clothing materials. Conventionally, thermoplastic elastomers such as polyurethane, polyester, and polyamide elastomer have been used as the stretchable melt-blown nonwoven fabric.

However, since the above-mentioned materials are hygroscopic materials, they need to be pre-dried in the melt-blowing process or degassed in the plasticizing process of the resin. Has the problem of adversely affecting That is, it is necessary to dehumidify the moisture in the air during the plasticizing extrusion process or to seal with dry air or dry nitrogen gas. This moisture management is extremely important in the production of melt blown nonwoven fabrics, but even with such dehumidification, the incorporation of a very small amount of moisture is unavoidable in industrial-scale production. There is a problem that the polymer is easily hydrolyzed by the heat of the above, and the produced monomer adheres to a die or a nonwoven fabric collection net during melt blowing, thereby impairing long-term continuous operation. In addition, the upper limit of the process heat resistance temperature of the above-mentioned material is 300 ° C. If it exceeds this, thermal decomposition of the polymer is promoted. For this reason, there is a limit to reducing the melt viscosity by increasing the temperature in order to reduce the fiber diameter.

[0004] As a method of solving the above problem, it is possible to reduce the burden of moisture management and to avoid a decrease in productivity due to thermal decomposition by using a polyolefin-based material as a material imparting elasticity. Are being considered. Low-density polyethylene is an example of a polyolefin material having elasticity and suitable for the melt-blown nonwoven fabric. However, if the density of polyethylene is high, the elasticity of elasticity is impaired, and it is necessary to reduce the density as much as possible. However, even if the density is selected in this way, the nonwoven fabric itself has elasticity, so that during the production of the nonwoven fabric, residual tension is generated in the roll product due to the tension when it is wound up on the roll, and this is chronologically difficult. The non-woven fabric is wrapped around the web, and adjacent webs cause blocking, which significantly impairs the product value. In particular, this tendency becomes more significant as the density decreases. Therefore, although the flexibility, elasticity and resilience of the nonwoven fabric are increased by lowering the density, there is a problem that the blocking property also increases.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a stretchable melt-blown nonwoven fabric using low-density polyethylene, which is not only made of a nonwoven fabric made of ultrafine fibers having excellent stretchability, but also excellent meltblown properties and antiblocking properties. To provide.

[0006]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, a composition comprising a low-density polyethylene having a specific density and a styrene-based elastomer and polypropylene mixed therein. The present inventors have found that a melt-blown nonwoven fabric having appropriate stretchability and antiblocking properties can be obtained by using, and the present invention has been completed. That is, in the present invention, (A) the density is 0.860
An elastic melt-blown nonwoven fabric comprising a composition containing 70 to 90% by weight of a low-density polyethylene resin of 0.9 to 0.920%, (B) 5 to 10% by weight of a polypropylene resin, and (C) 5 to 20% by weight of a styrene-based elastomer. .

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

1. Raw Material Resin Composition (1) (A) Low-Density Polyethylene The (A) low-density polyethylene used in the present invention must have a density of 0.920 or less in order to enhance the recovery of the elasticity of the nonwoven fabric. As the low-density polyethylene in the present invention, a linear type polyethylene has a molecular skeleton, and as a monomer for copolymerizing ethylene, a copolymer with a higher α-olefin such as butene-1, 4-methylpentene-1, and octene-1 is used. Polymers are of interest. The density is determined by these monomers and their amounts, and in the present invention, the range of 0.860 to 0.920 is targeted. If the density exceeds this range, the elasticity and resilience deteriorate.

[0008] As a method for producing the low-density polyethylene used in the present invention, a metallocene-catalyzed LDPE capable of controlling the structure of polyethylene at a molecular level is used.
Is preferred. In this technique, the molecular weight distribution is narrow, the amount of low molecular weight substances is small, and since the comonomer is evenly grafted to each molecule, the blocking property is low as compared with the conventional process.

A specific production method is disclosed in
19309, JP-A-59-95292, JP-A-60-35005, JP-A-60-35006
JP-A-60-35007, JP-A-60-35007
JP-A-35008, JP-A-60-35009, JP-A-61-130314, JP-A-3-16308
No. 8, EP-A-420,436, U.S. Pat. No. 5,055,438, and WO 91/04257, namely a metallocene catalyst, Metallocene / alumoxane catalyst or, for example, WO
No. 92/07123, a catalyst comprising a metallocene compound and a compound which reacts with a metallocene catalyst to form a stable ion is used, and ethylene having a main component and a subcomponent having 3 to 18 carbon atoms are used. Examples thereof include a method of copolymerizing with an α-olefin.

(2) (B) Polypropylene The (B) polypropylene used in the present invention is a homo-polypropylene which is a propylene polymer or copolymer, or a random copolymer which is a copolymer with another α-olefin, particularly ethylene. Examples include polymers and block copolymers. In the present invention, the purpose of adding polypropylene is to impart anti-blocking properties. That is, by blending polypropylene with low-density polyethylene, highly rigid polypropylene is dispersed in the low-density polyethylene phase to form a reinforcing body, and blocking caused by tight tightening is prevented. Further, by using a high-flow polypropylene having a melt flow rate (hereinafter referred to as MFR, 230 ° C., 2.16 kg load) of 40 or more, the apparent flow property of the low-density polyethylene phase of the main material can be improved. it can. In addition, polypropylene melt melt viscosity is reduced by thermal molecular cutting at the stage of plasticizing the resin in the melt blow, so that the melt viscosity in the melt blow is made more and more preferable. This makes it possible to obtain a stretchable polyethylene nonwoven fabric made of a small-diameter fiber that has never existed before.

(3) (C) Styrene-based elastomer The (C) styrene-based elastomer used in the present invention broadly includes an elastomer obtained by copolymerizing styrene with another comonomer. As the comonomer, a diene compound such as butadiene, isoprene, or chloroprene; an olefin such as ethylene, propylene, butene, or hexene; or a monomer copolymerizable with styrene such as (meth) acrylic acid or (meth) acrylic acid ester may be used. it can. Among these, a block copolymer type composed of blocks of a hard part and a soft part is preferable. In particular, a styrene-olefin-block copolymer is preferable because it functions as a compatibilizer for improving the affinity between low-density polyethylene and polypropylene. The styrene-olefin block copolymer has a polystyrene block phase at both ends of one molecule, and an olefin-based elastomer phase introduced into an intermediate phase. That is, a styrene-polybutadiene-styrene copolymer (SBS) whose intermediate phase is a polybutadiene-based copolymer and a styrene-polyisoprene-styrene copolymer (SBS) whose intermediate phase is a polyisoprene-based system
IS), a styrene-ethylene-butylene-styrene copolymer (SEB) in which the intermediate phase is a hydrogenated polyolefin
S), styrene, ethylene propylene, styrene (SE
PS). In addition to the above-mentioned styrene / polyolefin / styrene triblock copolymer, styrene / ethylene propylene diblock copolymer (SEP) and hydrogenated butadiene rubber (H
SBR) and the like are also included in the scope of the present invention.

In the composition of the present invention, the styrene-olefin-copolymer elastomer has a polyolefin elastomer phase contained therein which has an affinity for both low-density polyethylene and polypropylene resins, and a phase of both resins. It is considered that the polystyrene phase has elasticity and hardness in addition to improving the solubility, and fulfills the function of imparting anti-blocking properties. That is, if a small amount of polypropylene is blended with low-density polyethylene in a small amount, the elasticity of the entire nonwoven fabric is reduced, and an unthinned coarse polymer mass called a shot is generated in the melt-blown nonwoven fabric. This means that polyethylene and polypropylene are originally incompatible with each other, and with a simple extruder blend, the polypropylene dispersed in the polyethylene phase does not shrink, and the dispersion diameter is larger than the fiber diameter achieved by melt blowing. This is because the spinning state immediately after being discharged from the nozzle is not stable. Therefore, by blending a styrene-based elastomer as a compatibilizer with a mixture of low-density polyethylene and polypropylene, not only does the elasticity and elongation of the low-density polyethylene of the main material improve without impairing the tensile strength, but also It is considered that the effect of the styrene phase reduces blocking.

(4) Composition ratio of (A), (B) and (C) In the present invention, the composition ratio of (A) low-density polyethylene, (B) polypropylene, and (C) styrene elastomer is low-density polyethylene. 70 to 90% by weight, preferably 75 to 90% by weight, 5 to 10% by weight of polypropylene, 5 to 20% by weight of a styrene elastomer,
Preferably it is 5 to 15% by weight. Outside the above range, a stretchable melt-blown nonwoven fabric having the desired performance of the present invention cannot be obtained.

(5) Other Ingredients In addition to the polypropylene, the composition of the present invention further comprises other polyolefins such as high-density polyethylene, medium-density polyethylene, and other polypropylenes as long as the function of the present invention is not impaired. be able to. Further, the composition of the present invention can be used by mixing commonly used additives such as a coloring agent, an antioxidant, and an ultraviolet absorber, or an inorganic filler.

2. Method for Producing Nonwoven Fabric In the present invention, a nonwoven fabric made of uniform and small diameter fibers with few shots can be produced by directly connecting a twin screw extruder to a melt blow die. In other words, the raw resin charged into the twin-screw extruder is highly melt-kneaded, and these different resins are quickly compatibilized. Similarly, the high-speed rotating screw quickly becomes a high-temperature molten state by high-shear heat generation. Is introduced into the die as it is. For this reason, the resin is discharged into a high-speed airflow in a low-viscosity state, becomes extremely thin fibers, and can form a nonwoven fabric. In addition,
When the kneading capacity is low, particularly when a single screw extruder is used, a material obtained by kneading these materials in advance and compounding them is used.

3. Stretchable meltblown nonwoven fabric The stretchable meltblown nonwoven fabric according to the present invention has a density of 0.1%.
Since it is mainly made of low density polyethylene having a density of 860 to 0.920, it has excellent elasticity and elasticity recovery property, and contains polypropylene, so it has excellent anti-blocking property, and because it contains a styrene elastomer as a resin compatibilizer, polyethylene and polypropylene are used. Excellent kneading compatibility
At the same time, it can be adjusted to an appropriate plastic state, so that a nonwoven fabric composed of uniform fibers with few shots and spitters can be produced, and a nonwoven fabric with few shots and composed of ultrafine fibers of 3 to 10 μm can be obtained. The average diameter of the constituent fibers of the nonwoven fabric can be changed in the range of 3 to 10 μm by changing the production conditions of the nonwoven fabric, for example, the discharge rate, the extruder barrel temperature, and the like. Has features. Therefore, the stretchable melt-blown nonwoven fabric obtained by this method is used for applications such as sanitary materials, diaper materials, and clothing materials by utilizing its stretchability and air permeability. In recent years, polyurethane with elastic recovery has been developed,
Further, the present invention can be applied to fields where polyester elastomers and polyamide elastomers have been used as materials.

[0017]

The present invention will be described in detail with reference to the following examples.
In addition, the measuring method is as follows. (1) Shot: 10 arbitrarily cut out from a nonwoven fabric web
The number of shots contained in the web of cm square was visually counted and judged according to the following criteria. : 0 to less than 3 ×: 3 or more (2) Anti-blocking property: Cut the non-woven fabric into a 10 cm square, stack 5 sheets, and apply a 50 g / cm ² pressure evenly to the steel sheet. After holding the sample and leaving it in an oven at 40 ° C. for 24 hours, the state when the sample was peeled was determined according to the following criteria. : The base material peels without breaking. ×: The base material is broken. (3) Tensile strength: A sample having a width of 50 mm and a basis weight of 70 g / m ² was subjected to a strength test using a constant-speed tensile tester according to JIS 1079 (Testing method for chemical fiber fabrics). (4) Elongation: Using a constant speed tensile tester, span interval 100
The elongation at break was determined by dividing the elongation at break by the span interval. (5) Elongation recovery rate: Using a constant-speed tensile tester, stretching at a span interval of 100 mm and an elongation speed of 100 mm / min, 50 m
After elongating the sample for 3 minutes and maintaining the state for 3 minutes, the length S of the sample when the sample was removed from the tester and became non-tensile was obtained and calculated by the following equation. Elongation recovery rate (%) = (200−S) / 100 × 100
(%)

The main materials used in the embodiments of the present invention are as follows. 1) Low density polyethylene: ENGAGE 8401 (0.862 density, MI3
0, comonomer: octene-1, manufactured by Dupont Dow Elastomer Co.) ENGAGE 8403 (density 0.913, MI3
0, comonomer: octene-1, manufactured by Dupont Dow Elastomer Co.) kernel KE027 (density 0.895, MI1)
6, comonomer: butene-1, manufactured by Nippon Polychem) 2) polypropylene: homopolypropylene (MFR40) manufactured by Nippon Polychem. 3) Styrene elastomer ・ SEBS: KRATON G-1726 (styrene content 30%, MFR65, manufactured by Shell) ・ SIS: KRATON D-1117 (styrene content 17%, MFR106, manufactured by Shell) ・ SEPS: Septon 2002 (styrene) Content 30
%, MFR70, manufactured by Kuraray Co., Ltd.)-Hydrogenated SBR: DYNARON 1320P (styrene content 10%, MFR 3.5, manufactured by Nippon Synthetic Rubber Co., Ltd.)

Examples 1 to 9 and Comparative Examples 1 to 5 A composition prepared by blending low-density polyethylene, polypropylene and styrene-based elastomer in the proportions shown in Table 1 was heated and melted by an extruder, and introduced into a die. The extruded resin was made into a fibrous form by blowing into a high-temperature, high-speed airflow from the arranged nozzles, and this was accumulated on a conveyor, and a melt-blown nonwoven fabric having a basis weight of 70 g / m ² was formed by self-adhesion of the fibers. Tables 1 and 2 show the evaluation results of the nonwoven fabric.
In addition, the used apparatus and operating conditions are as follows.

[Apparatus] 1) Extruder: twin screw kneading extruder, screw diameter 30 mm. 2) Die: 0.4 m hole diameter aligned in a straight line at the die tip
m nozzle holes, 3 nozzles per inch
It has 0 holes and a total length of 250 mm. 3) Conveyor: The screen on the conveyor is 1 to 50 m /
While moving at a speed of one minute, the fibers are captured to form a nonwoven fabric. The basis weight and thickness of the nonwoven fabric are set according to the conveyor speed and the amount of resin discharged from the die.

[Operating conditions] Extruder barrel temperature 300 ° C. Screw rotation speed 300 rpm Discharge rate 5 kg / h Die temperature 300 ° C. Die-screen distance 200 mm Air temperature 290 ° C. Air flow rate 5-10 m ³ / min

[0022]

[Table 1]

[0023]

[Table 2]

As is evident from Table 1, the melt blown nonwoven fabric made of the low-density polyethylene, polypropylene and styrene-based elastomer composition within the scope of the present invention has few shots and is excellent in anti-blocking properties, elongation and elongation recovery. It is a stretchable meltblown nonwoven fabric (Examples 1 to 7).
On the other hand, low-density polyethylene alone has poor anti-blocking properties (Comparative Example 1). When only polypropylene is added to low-density polyethylene, shots occur frequently, anti-blocking properties are poor, and stretchability is lost (Comparative Example 2). 3), when only a styrene elastomer is added to the low-density polyethylene, shots occur frequently, the anti-blocking property is poor (Comparative Example 4), and when the amounts of the polypropylene and the styrene-based elastomer added to the low-density polyethylene are small,
When the anti-blocking property is poor, the elongation recovery rate is low (Comparative Example 5), and the amount of polypropylene added to the low-density polyethylene exceeds the range, shots occur frequently (Comparative Example 6).

[0025]

The stretchable melt-blown nonwoven fabric according to the present invention is made of low-density polyethylene as a main material, so that it has excellent stretch elasticity recovery, contains polypropylene, has excellent anti-blocking properties, and contains a styrene-based elastomer. A nonwoven fabric composed of uniform fibers with little shots and spitters can be produced. Therefore, the stretchable melt-blown nonwoven fabric obtained by the method of the present invention is used for applications such as sanitary materials, diaper materials, and clothing materials by utilizing its stretchability and air permeability.

Claims (1)

[Claims] (A) 70 to 90% by weight of a low density polyethylene resin having a density of 0.860 to 0.920, (B) 5 to 10% by weight of a polypropylene resin, and (C) 5 to 20% by weight of a styrene elastomer. A stretch melt blown nonwoven fabric comprising a composition containing: