KR820002273B1 - Polypropylene endless loop and the method therefor - Google Patents

Abstract

Polypropylene endless loops, useful as packaging bag, were prepd. by extrusion of polypropylene chips for tube sheet, which was cut off with thickness 0.05-0.06mm, length 15-30mm and drawn horizontally 4 times and twisted together to give polypropylene endless loops with tensile strength 615kg.

Description

Method for producing polypropylene endless loop

1 is a blow molded polypropylene tube

2 is an individual loop formed by cutting the tube of FIG.

FIG. 3 shows the individual loops cut after stretching the tube of FIG. 1 laterally.

4 is an endless loop formed by twisting the drawn lour of FIG.

The present invention relates to a method for producing a polypropylene endless loop.

Polypropylene loops, cords, colors, and the like have been widely used for packaging, but there are currently no known endless means.

The present invention relates to a process for producing a polypropylene endless loop for packaging, in particular a polypropylene endless loop attached to a magnetic tension plastic bag having a length of 7.5 to 35 cm and a tensile load of at least 6 kg.

According to the method of the present invention, a polypropylene raw material is blow-molded to form a tubular sheet, the sheet is cut to an appropriate length, made into individual loops, and stretched laterally with respect to the axis of a tube formed of at least four times the equipment. The twisted loop is then twisted to produce the desired endless loop.

According to another method of the present invention, the polypropylene raw material is blow-molded into a tube-like sheet, and then the sheet is laterally stretched with at least four times as much equipment, and then cut or slit into an appropriate length to obtain individual loops. And subsequently twisting the sheet into an endless loop.

Blow molding treatment of the polypropylene is carried out by a known technique by a known blow molding machine, but the molded polypropylene tubular sheet according to the present invention for producing a desired loop has a thickness of 15 to 50 mm, preferably 20 to 30 mm. It has a width of 0.03 to 0.1 mm and preferably a thickness of 0.05 to 0.06 mm. Here, the width is the length measured in the transverse direction, that is, the tube-like sheet is folded into two layers closely overlapped with each other to form a flat sheet shape, and then measured radially from one side thereof.

In the first method as described above, the tube-like sheet is cut to a length of 10 to 60 mm, preferably 25 to 35 mm in the longitudinal direction to obtain individual tubes. Therefore, this longitudinal length of each tube becomes the width of the endless loop to be produced, and the width decreases slightly in the stretching in the transverse direction.

In the lateral stretching, a force is applied at a stretching ratio of at least 4, preferably 5 to 7, in the transverse direction of the endless tube, ie perpendicular to the longitudinal direction of the first cut tube. Here, the stretching ratio means the ratio of the transverse length of the loop after stretching to the length before stretching the sheet. When the draw ratio is 4 or less, the tension of the obtained endless loop is insufficient, whereas when the draw ratio is too large, the sheet is damaged beyond the draw limit.

The length in the transverse direction of the endless loop after stretching is in the range of 7.5 to 35 cm, preferably 10 to 20 cm.

Stretching in the lateral direction can be performed at an elevated temperature or an ambient temperature, preferably at 40 ° C. or lower.

The stretched endless loop thus obtained is twisted again in a suitable manner to obtain a desired twisted endless loop.

In general, the polypropylene endless loop for packaging should have a tension of about 1 to 5 kg, and the polypropylene of the present invention has shown that the tensile load at the time of breaking of the endless loop is greater than 8 kg. An endless loop has been found to be suitable for the purpose.

Example 1

A blow-molded polypropylene tubular sheet having a thickness of 0.055 mm and a width of 25 mm was cut in a loop of 35 mm in length. The length of the horizontal direction after extending | stretching a loop in the horizontal direction is as showing in Table 1. The width of the individual loops after stretching is in the range of 25 to 26 mm.

Finally, the results of the tension test by twisting the endless loop are shown in Table 1.

TABLE 1

Example 2

The process of Example 1 was repeated but the polypropylene tube was cut to a length of 30 mm.

The results are shown in Table 2.

TABLE 2

Example 3

The process of Example 1 was repeated but cut to a length of 25 mm polypropylene tube.

The results are shown in Table 3.

TABLE 3

As apparent from Table 3, when the polypropylene having a thickness of 0.055 mm was cut to have a length of 25 mm, that is, each endless loop having a width of 25 mm, the tension after stretching was slightly satisfactory. Therefore, in order to obtain a more satisfactory tension, it is preferable to use a thicker polypropylene tubular sheet or a wider endless sheet.

Claims (1)

Blow molded into a polypropylene tube sheet, stretched in the transverse direction at a stretch ratio of at least 4 times and then cut to a suitable length or first cut and stretched at the above ratios to obtain individual endless sheets, twisted to produce endless loops Method for producing a polypropylene endless loop, characterized in that.

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