JPS605458B2 - Method for manufacturing thermoplastic resin bands - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a thermoplastic resin band.

BACKGROUND ART Conventionally, thermoplastic resin bands for packaging, for example, have been manufactured by extruding a thermoplastic resin into a band shape using an extruder, and stretching the band-shaped extrudate in its length direction.

However, since such a band is simply stretched in one track along its length, its strength in the width direction is substantially reduced, and when the band is subjected to forces such as twisting, bending, and deflection, its length increases. There is a drawback that vertical cracks occur along the direction. In addition, in order to prevent this vertical cracking, there is a method of manufacturing a band in which the surface of the above-mentioned band-shaped extrudate is embossed and the molecular orientation is disordered in the length and width directions, but this method also has a cracking prevention effect. In addition, the green color of the band is embossed, making it look like a saw blade, so there is a risk of cutting your hands when packing. As a result of intensive research in view of the above-mentioned drawbacks of the conventional art, the present inventor has completed a method for manufacturing a thermoplastic resin band that eliminates the above-mentioned drawbacks.

An embodiment of the method of the present invention will be described below with reference to the drawings.

First, a plurality of band-shaped extrudates 31, 32, 33
extruded in the molten state as

Next, the extrudates 31, 32, and 33 are introduced into the cooling bath 4 to be rapidly cooled and solidified to a temperature below the softening temperature of the thermoplastic resin. A water tank is normally used as the cooling tank 4. Furthermore, extrudates 31, 32
, 33 are taken out from the cooling tank 4 and preheated by a preheating device 5 such as a hot roll, steam, or infrared heater. This preheating temperature may be in a range of not less than the softening temperature and not more than the melting temperature of the thermoplastic resin. Furthermore, if the extrudates 31, 32, and 33 contain water when being rolled and stretched, they tend to slip on the rolling rolls 6, making it impossible to roll and stretch them smoothly. It is made to be. Next, the extrudates 31, 32, 33 are passed through pinch rolls 10', 10'.
At the same time, the circumferential speed of the rolling roll 6 is increased to the rolling roll 61.
Since the arrangement is in the order of <rolling rotor 62 <rolling roll 63, it is gradually stretched in the length direction. Therefore, extrudate 3
The molecules are oriented in the length and width directions. In addition,
The rolling rolls 6 are not only shaped as shown in FIG. 1, but are also formed into a pair of upper and lower peripheral speeds in the order of rolling rolls 61<cm0 roll 62<rolling rolls 63<rolling rolls 64 as shown in FIG. Several sets of rolling rolls 6 may be used.
Further, the width of the extrudate 3 before and after rolling and stretching is not particularly limited, but it may be made several times the predetermined width after rolling and stretching, and then divided into a plurality of pieces by cutting it lengthwise. Note that when the extrudate 3 passes through the rolling rolls 6, it is usually laminated, rolled, and
It is preferable that the rolling rolls 6 are heated so that the stretching can be carried out quickly. Then, the extrudate 3 was put on a pinch roll 10″
, 10" and led to an annealing device 7, where it is heated to a temperature above the softening temperature and below the melting temperature to remove internal strains caused by rolling and stretching. After being passed through a cooling tank 8 and cooled to below the softening temperature, it is solidified. The extrudate 3 is taken up by take-up rolls 10, 10, and wound up by a winder 9. After rolling and stretching, the surface of the extrudate 3 may be made with fine irregularities to the extent that the edges do not become serrated. Next, embodiments of the present invention will be described.

〔Example〕

Polypropylene was used as the resin, and the resin was attached to the tip of an extruder (screw diameter: 50 mm, rotation speed: 881 p.m.), with three rectangular (thickness: 1.5 ribs, width: 2 ribs) discharge ports. was extruded into three strips from a three-stage closed mold at extrusion temperatures of 20 and 0, the extrudate was rapidly solidified in a water bath (20 qo), and then heated to 11,000 with an infrared heater.

Next, as shown in FIG. 3, the three strip-shaped extrudates are guided so as to be laminated between rolling rolls provided with two pairs of upper and lower rolls, and the three strip-shaped extrudates are rolled out between the first rolling rolls 61 and 62. The objects are laminated and integrated, rolled to 1.2 times in the width direction, and 1.2 times in the length direction. After being stretched in the length direction with the next rolling rolls 63 and 64, it was heated to 110°C in an annealing device and rapidly solidified in a water tank (2000) to a thickness of 1 cm and width. A two-piece polypropylene band was obtained.
3 At this time, rolling rolls 61, 62, 63, 64, pinch rolls 10'', 1
0'' and the circumferential speed of the take-up rolls 10, 10 are as shown in Table 1. Table 1 0 The obtained polypropylene band was not crackable and was particularly suitable for packaging heavy items.

As detailed above, in the present invention, since the extrudates are divided into a plurality of thin strips and extruded, they are cooled more thoroughly and the distortion that occurs during cooling is reduced compared to the conventional single thick strip extrudates. small.

In addition, the extrudate is heated, and then the extrudate is heated and passed between at least a pair of opposing rolling rolls whose circumferential speed is sequentially increased to simultaneously roll and stretch the extrudate into a strip.
As the density of the extrudate increases, the strength in the width direction improves by rolling, and it is possible to obtain a band in which longitudinal cracks are prevented along the length direction. It is well-balanced without shifting to one side, making it particularly suitable for packaging heavy items.

Furthermore, there is no need to cut your hand at the edge of the band, which has a serrated edge as in the conventional case.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing one embodiment of the manufacturing method of the present invention, and FIG.
The figure is a front view showing the shape of the mold used in the present invention, and FIG. 3 is an explanatory diagram showing another embodiment of the rolling roll used in the present invention. 1... Extruder, 2... Mold, 21, 22, 23... Discharge port, 3, 31, 32, 33... Extrudate, 4... Cooling tank, 5... Preheating device, 6, 61, 62, 63, 64...
- Rolling roll, 7... Annealing device, 8... Cooling tank, 9... Winding machine, 10... Take-up roll, 10'
,10″...pinch roll. Figure 1 Figure Figure 2) Figure 3

Claims (1)

[Claims] 1 A thermoplastic resin is extruded in a molten state into a plurality of strips from a mold 2 attached to the tip of an extruder 1 and having a plurality of discharge ports, and the plurality of extrudates 31, 32, 33 are placed in a cooling tank. 4
It is introduced into the interior and rapidly cooled and solidified, and then preheated with a preheating device 5,
Subsequently, while heating the plurality of extrudates 31, 32, 33, they are passed between at least a pair of opposing rolling rolls 61, 62, 63 at sequentially increased circumferential speeds to be laminated and integrated into a band shape, and are rolled and stretched. A method for producing a thermoplastic resin band, which is carried out simultaneously and further comprises stretching the rolled extrudate 3 5 to 10 times in the longitudinal direction to form molecular orientation in the length and width directions.