KR840000512B1 - Apparatus for forming a plastic film - Google Patents

Abstract

Apparatus for forming a thermoplastic film by blown extrusion comprises an extrusion die (2), having a circular die lip (3) and an air port (4); a cylindrical annealing chamber (6) and an air ring (7); a blow-off slit (16) and an upper plate ring (9) having openings for air passage; a guide plate (13) and pinch rolls (14); and an air flow rectifying cylinder (11) for cooling and stabilizing the blown tube.

Description

Improved Apparatus for Molding Plastic Films

1 is a cross-sectional view of a device used in the present invention.

2 is a cross-sectional view of a film forming apparatus provided with an air ring in the form of a horizontal flow.

3 is a graph showing the relationship between flow up ratio and hoge.

The present invention relates to an improved apparatus for forming a plastic film by extrusion of a blown film from a thermoplastic resin.

In the manufacture of tubular film by blown film extrusion, the resin melted in the extruder is extruded in a tubular form from a circular die, and the cooling air is ejected immediately after extrusion by ejecting cooling air to the outer surface of the tubular film. Cooling and solidifying the tubular film and winding the tubular film with a pinch roll. The plastic film produced by the apparatus has a wide range of uses, such as pavement construction, architectural design and agriculture. In most cases, even if the clarity of the plastic film is only slightly improved, it is desirable because the improvement of the cleanness becomes a factor in raising the value of the plastic film. Despite the relatively good cleanliness, low density polyethylene is not applicable in areas where polypropylene is widely available. The reason is that although polypropylene is expensive, it is the most clean among general purpose resins.

Improving the cleanliness and gloss of blown tubular films made by blown film extrusion has been one of the long-standing problems to be solved. As a method for solving this problem, for example, a device of chimneys or cylindrical bodies in which a tubular film coming from a die is maintained in heat or heating has been proposed. 37-1225 and 38-24593. However, this device is unsuitable for commercial production when chimneys are combined with conventional air rings because they do not have sufficient cooling to enhance the physical properties of the final film, process stability is not satisfactory, and productivity is also too low. On the other hand, various apparatuses for lowering cooling have been proposed, and some of these proposed apparatuses have been put into practical use as a "fast blown film extrusion method" to meet market demands that require a price reduction. For example, an apparatus for strongly cooling and stabilizing blown tubes by means of a very fine air flow rectifying cylinder having an air ring separated has been proposed (Japanese Patent Publication No. 47-4947). Moreover, improved devices have been proposed to change the airflow in the running direction of the tubular film and to enhance cooling by using an expansion cylinder which injects a second cooling air through the hole between the cylinder and the air ring. Japanese Patent Publication No. 52-12791 and Japanese Patent Publication No. 53-8339 and 54-8390.

Prior art literature has described devices capable of high speed molding to some extent by enhancing the cooling airflow and removing the instability of the tubular film. Indeed, some of these successfully improved the mechanical properties of the final film, but none of them significantly improved the optical properties, especially the cleanliness.

It is therefore an object of the present invention to provide an apparatus for producing extremely good tubular films having a high degree of cleanliness by blown film extrusion from thermoplastic resins.

According to the present invention, immediately after annealing a molten tubular film extruded from a die in a first enclosed space, the cooling air is ejected in a direction perpendicular to its axis to quench the bilateral surface of the tubular film, And the tubular film is expanded and solidified in the second sealed space during contact with the cooling air flowing in the same direction as the traveling direction of the film.

Moreover, in the apparatus of the present invention, the melt shoe extrusion die is provided with a blow die and slits, in which a circular die lip and an air port are installed, and an air ring is installed in contact with the annealing chamber and opened horizontally at the end of the circular air passage. There is a hole formed in the hole and / or the upper plate ring thereof, characterized in that the air flow conversion cylinder is provided on the outer side of the life on the upper plate ring.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In the following, the drawings of the present invention are described in detail with reference to the accompanying drawings. In FIG. 1, the extruder 1 is provided with a die 2 having an air port 4 and a die lip 3, which is extruded into the melt tube 5. The cylindrical annealing chamber 6, having a height of 150 to 700 mm and a diameter of 1.1 to 5 times the diameter of the die lip 3, is extruded from the die lip 3 and also melted in contact with the die 2. It is located at the outlet of the die 2 with the tube 5 fillet. The air ring 7 is located at the outlet of the annealing chamber 6 which is in contiguous contact with the annealing chamber 6. The air ring 7 is located at the outlet of the annealing chamber 6 in contiguous or hermetic contact with the annealing chamber 6. The airflow conversion cylinder 11 is located on the air ring 7. The guide plate 13 and the pinch roll 14 are provided to wind the cooled tubular film. The air ring 70 is provided with an air inlet 12 at a suitable position on the outer circumference thereof. The lower plate ring 80 and the upper plate ring 9 are fires in which cooling air is blown at right angles to the axis of the tube 5. It forms a horizontal cylindrical curved passage 17 which is in contact with the blown off slit 16. The upper plate ring 9 has a hole 10 in a portion surrounded by the airflow cylinder 11, The hole has a number of slits and / or pores 15. The hole can suitably adjust its opening, having a height of 150 to 500 mm and a diameter of 1.5 to 6.5 times the diameter of the die lip. The upright air flow conversion cylinder 11 is positioned to be sealed to the upper plate ring of the air ring 9. The air flow conversion cylinder does not contact them while the blown film is traveling therein, and the tubular film is venturi ( it is not subjected to excess inflation caused by the ventury effect. In some cases, in order to stabilize the tubular film, a guide roll is provided in front of the pinch roll 14. In the film forming apparatus of the present invention using the apparatus as described above, from the die lip 3 The extruded melt tubular film 5 is gradually heated or cooled through the annealing chamber to promote surface source activity without any change in the film shape. As soon as it crosses the top of the tube, the film ejected from the blow off slit 16 of the air ring 7 at right angles to the axis of the tube travels through the tubular film as it is fed from the hole 10 as it travels. As it is supplied from the hole 10, it is further cooled and solidified by the cooling air flowing out along the tubular film. Finally, the solidified tubular film is wound up by the pinch rolls 14.

Films produced by the above-described apparatus are generally very good in comparison with blown tube films commercially available. The improved cleanliness achieved with the apparatus of the present invention is contrary to the practice of past practice that vertical blowing of air into the tubular film is not followed. But. This past practice has proved to be unfounded as a result of combining a commercially available air ring with cooling air ejected from a more precisely installed hole. The high-resolution film obtained by the device of the present invention is characterized by (1) strong cooling by air from a constant life preserver, (2) improved stability of the tuboop film achieved by an airflow conversion cylinder, (3) vertical air It is believed that this is a result of the common effect of rapid removal of warm exhaust air generated as a result of quenching achieved by the ejection stage or (4) film cooling.

Although low-density polyethylene has many excellent properties, the present invention is different in terms of low-density polyethylene cleansing, in view of its widespread application because of its lack of purity than other plastic resins. This is very important in that it can compete with Suzy.

Example 1

As shown in FIG. 1, a tubular film was produced under the following conditions using a 40 mm extruder installed in the apparatus of the present invention. Diameter of circular die slits: 75 mm annealing chamber: height 200 mm, diameter 285 mm. Air ring: The upper plate ring has 15 small holes. The position of the frost line: The air flow conversion cylinder of the air ring: 300 mm in diameter, 200 mm in height. Air in the blowslit of the air ring: Outflow ratio of air in the hole of the upper ring of the air ring = 12: 1, of the air ring Air speed: 6.2m / sec, blown air temperature: 200c Film blowing speed: 23m / mm, ejection ratio: 2.0, film thickness: 0.04mm, raw material: molten paper shoe 2.4 and density 0.924 NUC-8150 [product of Nippon Unicar Co., Ltd.]

The transparency and gloss of the resulting film (standard diagram for optical properties) are shown in Table 1 below.

Comparative Example 1

The tubular film is produced under the same process conditions as in Example 1 except that the blowoff slits of the air ring are deformed as shown in FIG. The modified blow-off slits are called the so-called horizontal flow forms (the cooling air is blown out in the horizontal direction with the tubing of the film), which is said to give good results according to known literature. Contrary to anticipation, the resulting film certainly lacks transparency more than that obtained in Example 1. As for the transparency, the air ring used in Comparative Example 1 is superior to the usual one, but this does not enhance the film gloss as shown in Table 1 below. Low gloss results in a lack of cleanliness of the resulting film visually.

Comparative Example 2

Instead of using an annealing chamber and an airflow conversion cylinder, tubular films are prepared under the same conditions as in Example 1 with horizontal flow type air rings used for a wide range of applications. The resulting film has a transparency of 5.2, which corresponds to a good standard for commercial low density polyethylene films.

[Examples 2 to 8]

Example 1 is repeated using a slightly different resin under slightly different conditions. The extrusion temperature is changed to 170c in Examples 5 and 6 and 150c in Example 7. (Keep at 160c in other embodiments). NUC-8150, -8506, -8008, and DFD-0118 are all low density polyethylene manufactured by Unika Japan. NUC-3530 is an ethylene vinyl acetate copolymer manufactured by Unika Japan. Ultrex is an ethylene copolymer manufactured by Mitsui Petrochemical Co., Ltd. In addition, DGFA-7043 and -7042 are ethylene copolymers manufactured by Unika Japan.

[Comparative Examples 3 to 9]

Blown tube films are prepared from several kinds of resins using the same apparatus under the same conditions as in Comparative Example 2. In these examples transparency, gloss, melt index and density are measured according to ASTM D-1003, ASTM D-2457, ASTm D-1238 and ASTM D-1505, respectively. Air velocity is measured by an electromagnetic anemometer manufactured by Shinkokusai Dengyo.

3 shows the relationship between the ejection ratio and transparency observed in Comparative Examples 1 and 2 other than Example 2. FIG.

TABLE 1

Claims (1)

In the apparatus for molding a plastic film by blown extrusion from the thermoplastic resin, the melt resin extrusion die is provided with a thermoplastic eye lip and an aft, the cylindrical annealing chamber is installed concentrically on the outside of the die lip, The air ring is installed in contact with the annealing chamber, and has a hole formed in the blowoff slits and slits and / or formed in the upper plate ring thereof, which horizontally opens at the end of the air passage. An improved apparatus for molding a plastic film, characterized in that it is provided outside the hole on the upper plate ring.

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