KR20100086139A - Method of thin-film permeability inflation film and permeablity film with this method - Google Patents

Abstract

PURPOSE: An air-permeable inflammation film is provided to excellent mechanical balance and to improve waterproof and stability and to use as diaper and sanitary napkin. CONSTITUTION: A method for manufacturing an air-permeable inflammation film comprises: a step of extruding air-permeable film compound composition containing polyolefin resin and inorganic filler with a tri-layered inflation extruder comprising a center extruder(M), inner extruder(I), and outer extruder(A); a step of cooling the extruded material at room temperature; and a step of drawing the extruded material using a separate drawing device.

Description

Method of manufacturing ultra-thin breathable inflation film and breathable film produced by this method {Method of thin-film permeability inflation film and permeablity film with this method}

The present invention relates to a method for producing an ultra-thin breathable inflation film and a breathable film prepared by this method, and more particularly, to a method for producing a breathable film, a method of preparing a breathable film by mixing an inorganic filler with a polyolefin resin to form a film. The present invention relates to a method for producing a breathable film by stretching in the uniaxial or biaxial direction to form fine pores using an interface separation between a resin and a filler, and a breathable film obtained by the method.

In most cases, the breathable film is stretched in the uniaxial direction using a T-die extruder to produce a film. In this case, the polymer is oriented in the stretching direction, that is, the machine direction (MD), thereby improving tensile strength. On the other hand, on the other hand, the mechanical properties in the cross section direction (CD) are lowered, which causes the printing and hot melt coating defects during production due to the folding and wrinkles at both ends of the film during processing of the film.

In particular, the thinner the basis weight of film (the weight of film per unit of unit is: g / m2), the worse this phenomenon becomes. In particular, in recent years, global diapers and sanitary napkins such as P & G and Kimberly Clark have improved productivity through cost reduction. In order to reduce the weight (g / m2) of the diaper or sanitary napkin for more than 25%, there is a need for a more improved product having the same physical properties as the existing products.

In addition, in order to maintain the design graphic pitch length within a minimum of ± 3mm by a unique registration sensing mark during high-speed production of ultra-thin film, the initial tensile strength of the film is maximized and the elongation is minimized to minimize the pitch deviation. The pitch stability can be secured, but there is a problem in that the orientation is excessively increased in the machine direction (MD), so that the generation of holes in the film increases rapidly, resulting in a decrease in productivity due to an increase in the defective film.

In particular, in recent years, the use of ultra-thin film is a trend to add new urine and menstrual blood leakage test standards or to strengthen existing standards, which requires more uniform and finer control of the interface between the film and the inorganic filler when forming the film. Do.

Although the existing T-die extrusion molding method recognizes difficulty in satisfying the above requirements and there is no effective alternative method, most companies are trying to improve the quality while using the T-die extrusion method, but are facing limitations. Doing.

Inflation extrusion may be considered instead of T-die extrusion. The inflation extrusion method uses an inflation film extruder as shown in Fig. 1, in which the starting thermoplastic resin (c) is stored in the storage hopper (2). Under the command of the computer, the load cell 3 automatically supplies the thermoplastic resin to the feed hopper 4 according to the take-off speed of the inflation film. The thermoplastic resin (c) is fed from the feed hopper 4 to the extruder 5 with the screw 7 driven by the screw motor 6, melt kneaded and extruded upward from the head of the extruder. The blowing head 9 including the ring die d is provided in the head of the extruder 5 in the vertical direction via the direct coupling 8. Inflation (air pump) 12 is connected to blower head 9 via pipe 11 with solenoid valve 10 such that air is blown into the extruded resin tube to form a tubular bubble e.

The tubular bubble e is then expanded and cooled by air supplied from the cooling blower 14 through an air cooling ring 13 installed above the blowing head 9. The tubular bubble e is guided by a pair of guide tubes 15 and passed through a pair of nip rolls 17 driven by a take-up motor to obtain a flattened tube f.

The flattened tube f is introduced into the width measuring device 18, which measures the flat width by the width sensor 19, and then moves along the guide rolls 20, 21 to hold the reel holder of the winder 22 ( It is wound around a paper reel g supported by 23).

When the inflation film is used as a flat film, the flattened tube f is cut into the desired number of sheets and wound around each paper reel g 'supported by the reel holder 23. In inflation extrusion, the “blow-up ratio” refers to the ratio of the final inner diameter of the inflation tube to the outer diameter of the ring die. Thermoplastics generally expand when the expansion ratio is between 1.2 and 4.

In the above-described inflation extrusion method, the bubbles extruded from the ring die are generally cooled with air supplied through the air cooling ring 13 from the cooling blower and continue to expand until they reach the frost line F where the bubbles solidify. do. The bubble passes through the frost line, stops expansion and is treated with a fixed diameter. Reference numeral 1 is an inflation film extruder.

The film obtained by the inflation extrusion method can solve the problem of excessive orientation in the machine direction, which is the aforementioned problem of the film obtained by the T-die extrusion method, but the inorganic content such as calcium carbonate is 50 due to the nature of the compound for breathable film. It is very difficult to control the thickness of the film during production because it is very difficult to control the thickness, and also the productivity is very low because the production speed should be slowed down to the maximum even if the thickness is adjusted, and the relatively high molecular weight (process flowability in the compound composition) It is difficult to disperse inorganic materials, such as calcium carbonate, because polyethylene having a low melt index product, which is not good, must be used.

For this reason, most companies now produce breathable films by T-die extrusion.

The present invention as described above, the problem of lowering the tensile strength in the width direction (CD) due to the unbalance of physical properties in the machine direction (MD) and the width direction (CD) due to uniaxial stretching of the T-die extruded film, and decrease in heat resistance according to the ultra-thin film, Pitch stability, water resistance (test item for evaluating the degree of penetration of urine or water under constant pressure), and heat resistance (test item for evaluating the degree of film shrinkage when applying hot melt adhesive to bond the film and nonwoven fabric) ) And to provide advanced inflation breathable film without hole generation in high speed production line (400M / Min).

The present invention is to achieve the above object, it uses a three-layer inflation extruder having at least L / D of 30 or more. When the L / D is less than the above range, molding failure occurs due to insufficient kneading of the compound composition.

The die structure of the three-layer inflation extruder is shown in FIG. 2 and is composed of an internal extruder (Extrude I), a center extruder (Extrude M), and an external extruder (Extrude A). The diameter of the screw is larger than the screw diameter of the other two extruders since the center extruder has the main extrusion action. For example, if the screw diameter of the center extruder is 90mm, it is appropriate that the screw diameters of the other two extruders are about 70mm.

By the structure of such an extruder die of the three-layer structure, it is possible to control the cylinder and die temperature by a separate extruder for each layer of the film to be extruded. Controlling the cylinder temperature of the cent extruder by 10-20 ° C lower than the cylinder temperature of the internal and external extruders greatly improves the problem of bubble instability in film forming. This also solves the problem of the die line of the film (a type of failure in which streaks occur on the surface of the film when passing through the die of the film if the moldability of the film is unstable, resulting in a back deviation) and the surface smoothness problem.

In order to impart breathability to the film obtained through such a process, the film is produced and left at room temperature for at least 8 hours to finish crystallization of the film. The best breathable film can be obtained.

In the case of stretching equipment, it is preferable to mount a micro embossing roll capable of maintaining a film thickness of 10 to 20 micrometers, and a heating roller capable of precise temperature control at least 100 ° C. or more is preferably attached.

The breathable compound composition used in the present invention has a melt index of 2.0 to 2.5 g / 10 min, a density of 0.930 to 0.935 g / cm3, and a linear low density polyethylene resin of 40 to 50 parts by weight and a melt index of 3.0 with respect to 100 parts by weight of an inorganic filler. 40 to 50 parts by weight of linear low density polyethylene resin having a density of 0.920 to 0.925 g / cm3 and 5 to 10 parts by weight of titanium oxide, and 5 to 10 parts by weight of other antioxidants and compatibilizers, and an extrusion temperature of 180 After mixing in a supermixer using a twin screw extruder maintained at ℃ and melt-mixed extrusion to prepare a pellet form.

In addition, the present invention can effectively improve the above problems caused by the conventional T-die extruded film through inflation extrusion without using low-density polyethylene which is essential for improving the processability when forming the T-die extruded film. Use breathable compound compositions that do not use low density polyethylene.

When the low density polyethylene is not used, the heat resistance of the obtained film is remarkably improved. In the conventional T-die extrusion method, molding was not possible without using low density polyethylene, and thus low density polyethylene has been used while taking heat resistance reduction.

Compared to the T-die extruded breathable film which is the most common method for forming the breathable film of the present invention, the inflation-extruded breathable film has excellent initial strength of the film, especially the balance of physical properties between MD tensile strength and CD tensile strength. It is superior to die-extruded film, so it is possible to produce more stable and excellent diaper and sanitary napkin film according to the improvement of the resistance of the remark mark pitch, hot melt heat resistance and uniform pore formation required for ultra thin film. The breathable film obtained by the present invention has a tensile strength of 1700 g / in or more at the break of the machine direction (MD), and a tensile strength of at least 190 g / in at the break of the width direction (CD).

Hereinafter, the present invention will be described in detail, but the scope of the present invention is not limited to the following examples.

(Comparative Example 1)

45 parts by weight of a linear low density polyethylene resin having a melt index of 2.3 g / 10 minutes and a density of 0.930 g / cm3 with respect to 100 parts by weight of an inorganic filler, and a linear low density polyethylene having a melt index of 3.3 g / 10 minutes and a density of 0.920 g / cm3. Extrusion cylinder temperature in the T-die extruder with an extruder screw diameter of 150 mm using a compound composition composed of 45 parts by weight of resin, 7 parts by weight of titanium oxide, and 7 parts by weight of other antioxidants and compatibilizers, and an average temperature of 230 to 250 ° C. At 150m / min production speed at, 2.5 times uniaxially stretched in the MD direction to prepare a breathable film having a basis weight of 15g / m2, the results are shown in Table 1 below.

(Comparative Example 2)

In this Comparative Example, a breathable film having a basis weight of 20 g / m 2 was manufactured under the same conditions as in Comparative Example 1, and the results are shown in Table 1 below.

(Example 1)

In this example, the same air permeable compound composition as in the comparative example is used to measure the cylinder temperature in a three-axis multi-inflation extruder with a diameter of 90 mm for the center extruder screw, a diameter of 70 mm for the internal and external extruder screws, and a screw L / D of 30. Is 170 ° C on average, die temperature is 185 ° C on average, and the BUR (Blow Up Ratio) is a bubble expansion ratio of the film. The formed film was left at room temperature for 24 hours, and then stretched 2.5 times at 80m / min speed in a separate stretching equipment equipped with a micro-embossing roller at a speed of 95 to 100 ° C on an average basis. A breathable film of 15 g / m 2 was prepared and the results are shown in Table 1 below.

(Example 2)

In this example, a breathable film having a basis weight of 20 g / m 2 was manufactured in the same manner as in Example 1, and the results are shown in Table 1 below.

(Example 3)

In this embodiment, in principle, the same as in Example 1, but the draw ratio was drawn four times to prepare a breathable film having a basis weight of 15g / m2 after stretching, the results are shown in Table 1 below.

In addition, the measurement of the physical property of following Table 1 was measured by the following method.

* Tensile strength: Tensile strength at 5% elongation in the machine direction (hereinafter referred to as “MD”) and machine vertical direction (hereinafter referred to as “CD”) according to the method of ASTM-D 882 using our MTS tensile tester And tensile strength at break was measured.

* Tensile Elongation: Elongation at break along MD and CD directions was measured using our MTS tensile tester according to ASTM-D 882.

* Moisture Permeability: P & G Co. According to the cup measuring method, it was measured using calcium chloride under constant temperature and humidity conditions of 40 ° C. and 75% relative humidity. The unit is g / m 2 / 24hr.

* Film heat resistance: Cut the film into 100mm horizontally and vertically, and then remove it after leaving for 1 hour in a constant temperature oven at 80 ℃ to observe the color discoloration or deformation of the film with eyes. Scanning calorimeter was used to compare the melting temperature (Tm: melting temp ') and heat capacity (△ Hf: Heat Capacity).

* Appearance of film: The surface of film was classified according to the degree of smoothness and wrinkles when visual observation was observed on the fluorescent lamp tester according to the observation of foreign substances and carbides.

(Double-circle): In the case of 1 m or less of foreign matter within 1.0 x 3.0 mm <2> of carbide sizes in the film of the size of 1 m each in width and length.

(Circle): When there are less than 5 foreign substances within the size of 1.0 x 3.0 mm <2> in the film of the size of 1m each in width and length.

(Triangle | delta): When the carbide size is five or more foreign substances within 1.0 x 3.0 mm <2> in the film of the size of 1 m each in width and length.

* Film processability: It is a classification based on the uniform extrusion load and extrusion amount in the state of film production with smooth film appearance and no thickness imbalance.

(Double-circle): When a film is smooth and it is shape | molded to a uniform thickness, and film defects are performed satisfactorily without defects, such as a fish eye, a hole, etc.,.

(Circle): When the film thickness is a little uneven, but the film surface is smooth, Fish eye, Hole etc. are fine, there is no problem in film molding.

(Triangle | delta): When the thickness of a film is nonuniform, Fish eye and a hole generate continuously, and an extrusion load and an extrusion amount are nonuniform.

* Basis weight: The weight of the film per square meter.

1 is a cross sectional view of a conventional inflation film compressor,

2 is a structural diagram of a three-layer inflation extruder die used in the present invention.

* Explanation of symbols for the main parts of the drawings

1: inflation film extruder, 2: storage hopper

3: load cell, 4: feed hopper

5: extruder, 6: screw motor

7 screw, 8 coupling

9: blowing head, 10: solenoid valve

11: pipe, 12: air pump

13: cooling ring, 14: cooling blower

15: guide tube, 17: nip roll

18: width measuring device, 19: width sensor

20, 21: guide roll, 22: winder

23: reel holder, c: starting thermoplastic resin

d: ring die, e: tubular valve

f: flattened tube, g: paper reel

F: frost line, M: center extruder

I: internal extruder, A: external extruder

Claims (5)

The compound composition for breathable film containing the polyolefin resin and the inorganic filler is extruded by a three-layer inflation extruder consisting of a center extruder (M), an internal extruder (I), and an external extruder (A), and then cooled at room temperature. , The manufacturing method of the breathable film, characterized by stretching in a separate stretching equipment. The method of manufacturing a breathable film according to claim 1, wherein the L / D of each extruder is 30 or more. The cylinder temperature of the center extruder (M) is maintained at 10 ~ 20 ℃ higher than the cylinder temperature of the inner extruder (I) and the outer extruder (A) method of producing a breathable film. The compound composition of claim 1, wherein the compound composition has a melt index of 2.0 to 2.5 g / 10 min, a density of 0.930 to 0.935 g / cm3, and a linear low density polyethylene resin of 40 to 50 parts by weight and a melt index of 3.0 to 100 parts by weight of the inorganic filler. 40 to 50 parts by weight of linear low density polyethylene resin having a density of 0.920 to 0.925 g / cm3 and 5 to 10 parts by weight of titanium oxide and other antioxidants and 5 to 10 parts by weight of compatibilizer The manufacturing method of the breathable film to make. The breathable film is prepared by the method of claim 1 to 4, wherein the tensile strength at break in the machine direction (MD) 1700g / in or more and the tensile strength at break in the width direction (CD) 190g / in or more.

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