JPS6146301B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for reducing the longitudinal shrinkage rate of a heat-shrinkable synthetic resin tube, the purpose of which is to reduce the longitudinal shrinkage rate to zero or less (that is, to make the tube stretch in the longitudinal direction). During manufacture, heat-shrinkable synthetic resin tubes are inevitably stretched in both the vertical and horizontal directions due to the need for tubular stretching and tube withdrawal, so they have the property of shrinking not only in the circumferential direction but also in the longitudinal direction. 40% in the circumferential direction (30 seconds at 100℃, the same applies below)
In order to obtain a shrinkage ratio of , the shrinkage ratio in the vertical direction must be 7.5.
It was inevitable that it would be larger than %. Therefore, if such a tube is shrink coated on a cylindrical body such as a condenser, it will shrink in the vertical direction during shrinkage, resulting in inaccurate cover, or if left for a long time after coating, it will gradually shrink and become clogged. There were flaws. Therefore, in order to reduce the shrinkage rate in the longitudinal direction of the manufactured tube, the tube is heated while maintaining the shrinkage rate in the circumferential direction using the internal pressure of the tube due to air and the outer diameter regulating body provided on the outside of the tube. Attempts have been made to remove the shrinkage by contracting only in the vertical direction, but it is difficult to adjust the internal pressure with air and tends to be unstable, and the equipment for this tends to be large-scale. In view of the above-mentioned problems, the present invention aims to reduce the vertical shrinkage rate of a tube in a simple and extremely stable manner by using an inner diameter regulating object. An inner diameter regulating body is introduced into the inside of the tube, and the synthetic resin tube is heated and contracted around the outer periphery of the inner diameter regulating body while being continuously fed out by a pair of feeding rolls, and then rapidly cooled. It is characterized in that when the synthetic resin tube is taken up by a pair of take-up rolls, the take-up speed is lower than the delivery speed. By making the take-up speed of the heat-shrinkable synthetic resin tube smaller than the delivery speed as described above, the longitudinal tension acting on the synthetic resin tube on the inner diameter regulating body becomes minimal. When the synthetic resin tube is heat-shrinked around the outer periphery of the inner diameter regulating body, the shrinkage of the synthetic resin tube in the circumferential direction is suppressed by the outer diameter of the inner diameter regulating body. Therefore, although the shrinkage rate in the circumferential direction remains, since the tension in the longitudinal direction is minimal, it contracts freely in the longitudinal direction, and as a result, almost no shrinkage rate in the longitudinal direction remains. Moreover, since the contraction of the tube in the circumferential direction is maintained with extremely high precision by the outer diameter of the inner diameter regulating body, the longitudinal contraction rate of the tube can be easily adjusted by controlling the tube delivery speed and take-up speed. Moreover, since the outer diameter of the inner diameter regulator only needs to be extremely slightly smaller than the inner diameter of the tube before contraction, it is possible to minimize only the longitudinal contraction rate of the tube without reducing the circumferential contraction rate of the tube. . Furthermore, when the take-up roll speed is further reduced compared to the delivery roll speed, the heated part of the tube is compressed by the pre-heated part and the cooled part of the tube beyond the shrinkage rate, and is cooled and fixed as it is. . Therefore, according to the present invention, it is also possible to obtain a tube which has the property of extending in the longitudinal direction by heating. The following is an explanation using the drawings: Figures 1 and 2.
The figures show an example of a slightly modified apparatus for carrying out the invention, and equivalent parts in both figures are given the same reference numerals. 1, 1' are feeding rolls, 2, 2' are support rolls,
3 and 3' are holding rolls, 4 is a support, 5 is a connecting rod, 6 is an inner diameter regulating body, 6' is a conical end provided on the regulating body, 7 and 7' are take-up rolls, and 8 is a heat shrinkable body. 9, 9', 10, 10' are guide rolls, 11 is a heating fluid discharge nozzle, 12 is a cooling fluid discharge nozzle, and 13, 13' is a delivery roll. In the example of the apparatus shown in FIG. 1, the conical end 6' of the inner diameter regulating object 6 having a conical end 6' is directed toward the delivery rolls 1, 1', and the regulating object 6 is moved toward the holding rolls 3, 3'. , support 4, tube 8 together with connecting rod 5
The heated fluid discharge nozzle 1 is inserted into the tube 8 and held between the feed rolls 1, 1' and the support rolls 2, 2', and the heated fluid discharge nozzle 1 is directed outward of the tube 8 toward the regulating object 6.
1 and a cooling fluid discharge nozzle 12 are provided in order so that the tube 8 is heated and cooled in sequence. 7,
7' operates at a reduced speed compared to the delivery rolls 1 and 1'. In the case of this device example, the deceleration of the take-up rolls 7, 7' and the longitudinal contraction of the tube 8 cancel each other out, and the tube 8
Since the tube is taken up smoothly, there is no risk of the tube being folded over or pinched between the support rolls 2, 2' and the holding rolls 3, 3', and the work can be carried out smoothly. The tubes taken off from the take-up rolls 7, 7' have a longitudinal shrinkage ratio of zero or less. In the example of the device shown in FIG. 2, the centrally constricted delivery rolls 1, 1' are provided immediately after the support rolls 2, 2', and the delivery rolls 13, 13' and the support rolls 2, 2' holding rolls 3, 3' and support 4
is inserted, the connecting rod 5 passes through the support rolls 2, 2' and the delivery rolls 1, 1', and the regulating object 6 is inserted between the delivery rolls 1, 1' and the take-up rolls 7, 7'. Heated fluid discharge nozzle 1 toward the outside of the regulating object
1 and a cooling fluid discharge nozzle 12 are provided in order so that the tube 8 is heated and cooled in sequence. , these take-up rolls 7, 7' are connected to the delivery rolls 13, 1
3', it operates at a slower speed than the delivery rolls 1, 1'. In this device example, the feeding rolls 1, 1' are provided after the supporting rolls 2, 2', so that the tube 8 is actively fed out, so that the tube 8 is fed out actively between the supporting rolls 2, 2' and the holding rolls 3, 3'. This prevents malfunctions such as overlapping or pinching of the tube and allows the tube to advance smoothly, and also prevents the regulating object 6 from being placed between the feeding rolls 1, 1' and the decelerated take-up rolls 7, 7'. The tube 8 is sequentially heated and cooled along its circumferential surface and is sufficiently shrunk in the longitudinal direction, so that the tube taken off from the take-up rolls 7, 7' has a longitudinal shrinkage ratio of zero or less. When carrying out the method of the present invention, friction and resistance generated at parts such as the support rolls 2, 2' and holding rolls 3, 3' for holding the inner diameter regulating body in place prevent the inner diameter regulating body from moving upward. It is important to avoid applying tensile forces to the tube. That is, the support rolls 2, 2', etc. need to be provided behind the inner diameter regulating body as shown in FIG. 1, or in front of the feed rolls 1, 1' as shown in FIG. These devices are simpler and do not require a device for stabilizing the internal pressure, compared to the method of applying internal pressure using air, and can reduce the vertical shrinkage rate of the tube in an extremely stable manner. Next, specific examples of the present invention will be described. Example 1 An example is shown in which the longitudinal shrinkage rate of a heat-shrinkable tube is eliminated using the apparatus shown in FIG. In FIG. 1, a Teflon-coated cylindrical body with an outer diameter of 36 mm is used as the inner diameter regulating object 6, hot water at 90° C. is used as the heating fluid, and water at 20° C. is used as the cooling fluid. A semi-rigid vinyl chloride heat-shrinkable tube with a folded diameter of 61 mm and a thickness of 0.09 mm was treated using the apparatus shown in Figure 1. As a result, the shrinkage rate at 100°C for 30 seconds was as follows.

[Table] Example 2 Next, an example will be shown in which the longitudinal shrinkage rate of a heat-shrinkable tube was actually reduced using the apparatus shown in FIG. Second
In the figure, a Teflon round rod with an outer diameter of 10 mm is used as the inner diameter regulating object 6, hot water at 90°C is used as the heating fluid, and water at 20°C is used as the cooling fluid. Further, the speed of the delivery rolls 1, 1' was 10 m/min, the speed of the delivery rolls 13, 13' was 10 m/min, and the speed of the take-up rolls 7, 7' was 7 m/min. Under the above conditions, the longitudinal shrinkage of a heat-shrinkable tube made of semi-rigid vinyl chloride with a folded diameter of 16.5 mm and a thickness of 0.09 mm was reduced, and the shrinkage at 100°C for 30 seconds was as shown in the following table.

[Table] In this way, the shrinkage rate in the circumferential direction hardly decreases, and the shrinkage rate in the longitudinal direction is reduced to 0% or less.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an example of an apparatus for implementing the present invention, and FIG. 2 is a perspective view of a slightly modified example of the apparatus. 1 and 1' are feeding rolls, 2 and 2 are support rolls,
3, 3' are holding rolls, 4 is a support, 5 is a connecting rod, 6 is an inner diameter regulating object, 6' is a conical end, 7,
7' is a take-up roll, 8 is a tube, 11 is a heating fluid discharge nozzle, 12 is a cooling fluid discharge nozzle, 1
3 and 13' are delivery rolls.

Claims (1)

[Claims] 1. Introducing an inner diameter regulating body into the inside of a heat-shrinkable synthetic resin tube, heat-shrinking the synthetic resin tube around the outer periphery of the inner diameter regulating body while continuously feeding out the synthetic resin tube with a pair of feeding rolls, and then rapidly 1. A method for reducing longitudinal shrinkage of a heat-shrinkable synthetic resin tube, which comprises cooling the synthetic resin tube and then taking the synthetic resin tube with a pair of take-up rolls at a take-up speed lower than the delivery speed.