KR20010008468A - Manufacturing method of linear low density polyethylene spun-bonded fabric - Google Patents

Abstract

PURPOSE: A method for preparing linear low density polyethylene(LLDPE) spunbond non-woven is provided, to improve the melting strength and the smoothness. CONSTITUTION: The method comprises the steps of blending 90-95 wt% of LLDPE, 2-7 wt% of crystalline polypropylene, 2-3 wt% of white master bath chip by dosing; melt spinning the blend by using an extruder at 190-240deg.C; and hot pressing it with the condition of the line pressure of a hot press roller being 35 kg/cm, the hot press bonding rate being 10-14.2 %, and the temperature being 130-170deg.C. Preferably the LLDPE is such that the density is 0.931-0.936 g/cm¬2, the melting index is 23.9-30.4 g/10 min, the melting point is 110-130deg.C, the crystallinity is 30-45 wt%, and the molecular weight distribution is 3-4.

Description

Manufacturing method of linear low density polyethylene spun-bonded fabric

The present invention relates to a method for producing a spunbond nonwoven fabric that maintains the properties of linear low density polyethylene, and more particularly, to a spanbond nonwoven fabric having excellent melt strength and a flexible touch by using a blend structure of linear low density polyethylene and crystalline polypropylene. It relates to a manufacturing method of.

Conventionally, a method for producing a polypropylene spanbond nonwoven fabric as a method for producing an olefin resin based spanbond nonwoven fabric is widely known commercially. According to US Pat. No. 3,692,618, a polypropylene nonwoven fabric having excellent waterproof and soft properties for hygiene, especially a baby diaper, Spunbond using low density polyethylene (LDPE) or linear low density polyethylene resin (LLDPE) to give excellent soft properties of the backsheet portion made of synthetic fibers according to the tendency to feel like natural materials of disposable diapers. The development of nonwovens has been required, but the filaments are frequently cut when drawn due to low melt strength, which has made it difficult to commercialize.

In the present invention, while maintaining the properties of the linear low-density polyethylene (hereinafter referred to as "LLDPE") to produce a polyethylene nonwoven fabric by branding polypropylene in order to prevent the breakage of the filament during high-speed spinning, the object of the present invention is to By using a blend structure of crystalline polypropylene, an object of the present invention is to produce a nonwoven fabric having high-speed spinning and having a soft touch therefrom.

The present invention relates to a method of manufacturing a flexible polyethylene nonwoven fabric, wherein the linear low-density polyethylene blended can classify LLDPE according to the type of alpha-olefin, and typical alpha-olepan types are propylene butene-1, hexene-1, and octene. In general, the longer the branch length, the higher the mechanical properties. Therefore, the LLDPE used in the present invention contains 1 to 10% by weight of octene-1 having 4 to 8 carbon atoms in the branch, and the density is A polymer having 0.931 to 0.936 g / cm 3, a melt index of 23.9 to 30.4 (10 g / min), and a heat of fusion of 25 cal / g is used.

The raw material and blending ratio used in the present invention is 90/7 to 95/2 wt% of LLDPE and polypropylene resin, and it is soft to contain 2 to 3 wt% of master batch chip to improve color and radiation flowability. Polyethylene long fiber spanbonded nonwoven fabric having excellent properties is obtained.

Background Art Conventionally, a method of manufacturing a spunbond nonwoven fabric using a thermoplastic polymer, in particular a polyolefin resin, is widely known. When the non-woven fabric is produced by complex spinning of different polymers with different melting temperatures, the polymer having a relatively low melting temperature acts as a binder to increase the strength of the nonwoven fabric, and the tactile property changes significantly according to the content of the low melting polymer. Spunbonded nonwoven fabrics using a bicomponent of medium density, polyethylene and low density polyethylene as low melting point composites have disadvantages of poor texture. In addition, when LLDPE obtained from a commercially available alpha-olefin copolymer having 4 to 8 carbon atoms is used as the low melting point portion, it exhibits a soft texture but is not suitable for manufacturing nonwoven fabric by high speed spinning yarn trimming. There are many problems.

U.S. Patent No. 4,644,045 discloses a method for producing a soft spanbonded nonwoven fabric using a linear low density olefin polymer, but the crystallinity of the linear low density olefin, the ratio of the natural number of dieswell to the melt index, etc. are presented and the linear low density olefin polymer is melted. The extruder temperature is shown at 185-215 ° C. However, this method has a low melt extrusion temperature and a high stretching force applied during spinning, resulting in filament cutting at an increase in spinning speed. Therefore, there are many defects in the nonwoven fabric, so that the uniformity of the web is not uniform, resulting in a nonwoven fabric of a low quality product.

U.S. Patent No. 5,068,141 introduces a continuous filament manufacturing method having excellent mechanical strength and soft properties using a linear low density polyethylene resin, but the polyethylene nonwoven fabric described above is composed of a linear low density polyethylene with a high speed air gun. It is known to manufacture by laminating onto a conveying belt drawn by stretching and thermally bonding with a heat treatment calender 15 to 30 ° C. lower than the melting temperature of the constituent fibers, but it is shown that the cross section of the constituent fibers is hollow or using a flat knitting yarn. In the case of the bicomponent filament, the composition of the sheath component is suggested to be a linear low density polyethylene and the core component is polyethylene terephthalate. However, when high-speed spinning of the linear low-density polyethylene proposed in the present invention alone, the melt tension is low and the filament is cut off. In the case of the hollow fiber or the flat yarn, the nonwoven fabric composed of the flat yarn has a poor form retention when the filament is stretched by the high speed air gun. Since the bonding area is larger than that of the circular section, the mechanical strength is excellent, but the soft characteristics are not good.

The present invention is to solve the above problems, and is a linear low density copolymer of ethylene and at least one kind of alpha-olefin having 4 to 8 carbon atoms, the density is 0.931 ~ 0.936g / ㎠, the melt index A dosing system containing 90 to 95 wt% of LLDPE having a heat of fusion of 25 cal / g or more and measuring 23.9 to 30.0 g / 10 minutes as measured by the method of ASTM D-1238, and supplying 2 to 7 wt% of crystalline polypropylene as a raw material. Polyethylene spunbond nonwoven fabric by blending, melting through an extruder and spinning into filaments through a mold.

In the present invention, the heat of fusion was analyzed using DSC (PORKIN-ELMER Co., Ltd.), and 5 mg of the sample was taken to obtain a DSC curve obtained by raising the scan rate to 20 ° C / min and raising the temperature from room temperature.

Spinning at 100 wt% of LLDPE resin is difficult to form the nonwoven web because the filament is cut when the spinning speed is high due to the high stretching tension given at high speed spinning. Therefore, in the present invention, in order to prevent trimming when the spinning speed is increased, melt spinning the polypropylene 2 to 7 wt% in an extruder or dispersing the polypropylene resin in the polyethylene chip itself in a 2 to 10 wt% sea island shape to melt spinning Let's do it.

The production of polyethylene spanbonded nonwovens using LLDPE, as is generally known, melt-spun polymers to form webs on a moving conveyor belt and bond them in a thermal or mechanical manner to form nonwovens. The melt index of LLDPE used to produce spanbonded nonwovens is 23.9 to 30.4 / 10 min, and the density is 0.931 to 0.936 g / cm 3.

1 is a manufacturing process of the linear low density polyethylene spanbond nonwoven fabric of the present invention.

<Explanation of symbols for main parts of drawing>

1: Spunbond Spinning Nozzle 2: Spunbond Filament

3: nonwoven web 4: upper embossed roller

5: lower embossed roller 6: spunbond nonwoven fabric

7: Conveyor Belt

Polyethylene nonwoven fabrication is produced in a spanbond spinning assembly as shown in FIG. 1 and, in detail, polyethylene is uniformly blended with a certain amount of polypropylene when fed to the extruder. The molten blend body is spun through a confinement of countless holes and stretched by its own weight and the aerodynamics of the venturi tube to form a filament of approximately 20-25 microns. The stretched polyethylene filament is formed and transported by air pressure drawn from below on a continuously moving conveyor belt to be maintained at 130 to 170 ° C, and the surface of the embossed roller with a flake pattern having a difference of 10 ° C is smooth. Thermally bonded by the lower embossed roller to produce the polyethylene spanbond nonwoven fabric of the present invention.

Hereinafter, the present invention will be described in detail with reference to Examples.

Various physical property measurement and evaluation values in an Example are analyzed by the method shown next.

(1) Tensile strength:

Ten tensile specimens of 5cm in width and 10cm in length were measured individually at the tensile speed of 100cm / min according to the street method of ASTM D1682-64 using United's tensile strength. Adopt average value.

(2) Tensile elongation: The elongation of maximum tensile strength yarn measured by the method of (1) is to be obtained.

(3) Melt index (Ml): Measured according to the description in ASTM D1238 (E).

(4) Tear strength is measured by the trepezoid method of ASTM D2253.

(5) Molecular weight distribution: Measured by GPC.

(6) Melting temperature: measured by DSC.

Hereinafter, the present invention will be described with reference to Examples and Comparative Examples.

Example 1

95 wt% of LLDPE (Japan petrochemical products) with a density of 0.931 to 0.936 g / cm 3 and Ml of 25 g / 10 min. Improves the flow of melt and 2 wt% of polypropylene having a density of 0.90 g / cm 3 and 36 g / 10 min of Ml. To make a white master batch 3wt% melt brand in an extruder with a melt spinning temperature of 220 ℃ to spin continuously into a filament through a plurality of orifices, a honeycomb chamber to crystallize the filament Through the air suction device installed at the lower part of the conveyor belt, which releases the cooling air through and continuously moves the filament, the filament is increased in speed as it passes through the venturi tube (the air movement passage is narrowed), and is stretched downward to be required as the fiber. It has strength and elongation characteristics. Polyethylene filaments drawn by aerodynamics are laminated onto continuously moving conveyor belts to form webs and the webs are thermally bonded to impart mechanical properties and morphological stability. The weight of the web to be formed is determined by the discharge amount and the production speed. In Example 1, the basis weight was produced at 18 to 30 g / m 2, and the line pressure of the heat welding roll was 35 kg / cm, the heat bonding bonding rate was 14.2%, The thermal fusion temperature was produced at 120 ℃. Production conditions and physical properties are shown in Table 1 and Table 2.

Example 2

The LLDPE used in Example 2 is manufactured by dispersing polypropylene in polyethylene (Daelim Industry) during chip manufacturing, unlike the method in which extruders are blended by supplying chips of polyethylene and polypropylene, respectively. The dispersion ratio of linear low density ethylene and polypropylene was set to 90 / 7wt%. Spinning temperature and heat fusion were produced under the same conditions as in Example 1. Production conditions and physical properties are shown in Table 1 and Table 2.

Comparative Example 1

Polyethylene and polypropylene ratios were 88% polyethylene, 10% polypropylene, and 2% white M / B. The melt spinning temperature was 220 ° C, the spinning speed was 7000m / min, and the filament cooling conditions, production speeds, and heat-sealing conditions were performed. It carried out similarly to Example 1. Table 1 and Table 2 show the production conditions and the physical properties.

Comparative Example 2

Chips prepared in the random dispersion mixing ratio of polyethylene and polypropylene of the chip used in Example 2 were 90 / 7wt%, and the melt spinning temperature was 250 ° C, the spinning speed was 7000m / min, and the filament cooling conditions, production speed and heat Fusion conditions were the same as in Example 1. Table 1 and Table 2 show the production conditions and the physical properties.

Table 1. Manufacture conditions

Item Example 1 Example 2 Comparative Example 1 Comparative Example 2 PE / PP Mixing Ratio (wt%) 95/2 90/7 88/10 90/7 Spinning temperature (℃) 220 220 220 250 Spinning speed (m / min) 6000 6000 7000 7000 Discharge amount (kg / hr) 585 585 585 585

Table 2. Physical property results according to the examples

Item Example 1 Example 2 Comparative Example 1 Comparative Example 2 Basis weight (g / ㎡) 18 25 18 25 Tensile Strength (kg / 5㎝) MD 1.8 2.1 1.20 1.55 CD 1.2 1.5 0.32 0.82 Tensile Elongation (%) MD 60 61 200 210 CD 70 73 170 180 Thickness (mm) 0.14 0.18 0.14 0.19 Island (Denia) 3.01 3.04 4.01 4.08 Tear strength (kg) MD 0.2 0.39 0.18 0.40 CD 0.27 0.45 0.20 0..47 Lecture degree (mm) 40.2 45.5 42.3 46.5 Emission of trimming none none Large quantities Large quantities

The present invention is a spunbond nonwoven fabric of polyolefin resin mainly composed of linear low density polyethylene having excellent softness, and has excellent melt strength, enables high-speed spinning and has a soft touch, thereby obtaining an excellent spunbond nonwoven fabric.

Claims (3)

90 to 95% by weight of linear low density polyethylene (LLDPE), 2 to 7% by weight of crystalline polypropylene and 2 to 3% by weight of white master bath chip are blended through dosing, and the temperature of the extruder is 190 to 240 A method for producing a linear low density polyethylene spanbond nonwoven fabric, characterized in that it is melt spun and heat bonded at a temperature of 0C. The method according to claim 1, The low density polyethylene on the shipboard has a density of 0.931 to 0.936 g / cm 3, a melt index (Ml) of 23.9 to 30.4 g / 10 min, a melting point of 110 to 130 ° C., a crystallinity of 30 to 45% by weight, and a molecular weight distribution (MWD) of 3 to 4 A process for producing a linear low density polyethylene spanbond nonwoven fabric, characterized by the above-mentioned. The method according to claim 1, In order to give the thermal bond strength and form stability of the polyethylene spanbonded nonwoven fabric, the line pressure of the heat-sealing roller is 35 kg / cm, the heat-bonding bonding rate is 10 to 14.2%, and the heat-sealing temperature is 130 to 170 ° C. Process for producing polyethylene spanbond nonwovens.