Method and device for manufacturing a heat-shrinkable tube

Abstract

The application discloses a preparation method and device of a heat-shrinkable tube. The method comprises the following steps: first inflation of an initial heat-shrinkable tube, so that the radial dimension of the heat-shrinkable tube is expanded to a first intermediate size; intermediate heat treatment of the heat-shrinkable tube after the first inflation, so that internal stress generated in the heat-shrinkable tube during the first inflation is released; and second inflation of the heat-shrinkable tube after the intermediate heat treatment, so that the radial dimension of the heat-shrinkable tube is expanded to a target final size. The device comprises a traction module, a first heating module and a second heating module. The heat-shrinkable tube prepared by the application can significantly reduce the axial shrinkage rate while maintaining a high radial shrinkage rate, and the appearance of the heat-shrunk tube is more smooth. Moreover, the whole process does not need to modify the raw material, and the raw material cost and process complexity are not increased.

Description

Technical Field

[0001] This invention belongs to the field of heat shrink tubing forming technology, specifically relating to a method and apparatus for preparing heat shrink tubing. Background Technology

[0002] During the use of heat shrink tubing, the heat shrinking temperature, axial shrinkage rate, and longitudinal shrinkage rate are the core functional indicators that determine its application scenarios. If you want to apply heat shrink tubing to other application scenarios, you need to adjust and control its heat shrinking temperature, axial shrinkage rate, and longitudinal shrinkage rate.

[0003] In related technologies, the above-mentioned properties are often improved by modifying the raw materials. For example, Chinese patent CN117567848A improves the heat shrinkage ratio by using modified raw materials. However, modifying the raw materials not only requires the development of new formulation raw materials, which increases costs, but may also require adjustments to the entire production process. Summary of the Invention

[0004] The purpose of this invention is to provide a method and apparatus for preparing heat shrink tubing to solve the problems in the prior art.

[0005] Therefore, the present invention provides a method for preparing heat shrink tubing, comprising: The initial heat shrink tubing is first inflated, causing the radial dimension of the heat shrink tubing to expand to a first intermediate dimension; The heat shrink tubing is subjected to intermediate heat treatment after the first inflation to release the internal stress generated during the first inflation process. The heat shrink tubing, after undergoing intermediate heat treatment, is then inflated a second time to expand its radial dimension to the target final size.

[0006] In some embodiments, the intermediate heat treatment temperature is higher than the temperature of the first inflation but lower than the melting point or decomposition temperature of the initial heat shrink tubing material.

[0007] In some embodiments, the first inflation ratio is 50% to 80% of the target final inflation ratio.

[0008] In some embodiments, the first inflation and / or the second inflation are performed under conditions higher than the glass transition temperature of the initial heat shrink tubing material.

[0009] In some embodiments, after the first and / or second inflation, the inflated heat shrink tubing is rapidly cooled and shaped.

[0010] In some embodiments, the interior of the initial heat shrink tubing is filled with an inert gas of 0 to 20 bar during the inflation process, and the heat shrink tubing is pulled at a traction rate of 0 to 10 mm / s.

[0011] On the other hand, an apparatus for manufacturing heat shrink tubing is also provided, comprising: A traction module for pulling heat shrink tubing along a first direction; A first heating module and a second heating module are arranged sequentially along the first direction; A first sizing tube, corresponding to the first heating module, is used to limit the heat shrink tube, which has been inflated for the first time, to a first intermediate size. The second sizing tube, which is provided in accordance with the second heating module, is used to limit the heat shrink tube, which has been inflated a second time, to the target final size. The second heating module performs intermediate heat treatment on the heat shrink tubing that has been processed by the first heating module.

[0012] In some embodiments, a third heating module and a third sizing tube are also included. The third heating module is disposed after the second heating module and is used to re-inflate or assist in shaping the heat shrink tubing.

[0013] In some embodiments, the temperatures of the first heating module and the second heating module are independently adjustable, and the adjustable temperature range of the second heating module covers a temperature range higher than that of the first heating module.

[0014] In some embodiments, the traction module includes a movable platform movable along the first direction, a clamp for holding or traction of the heat shrink tubing, and a gas needle for filling the heat shrink tubing with gas.

[0015] In some embodiments, a cooling device is also provided at the outlet of the first heating module and / or the second heating module, the cooling device being used to rapidly cool and shape the inflated heat shrink tubing.

[0016] Beneficial effects: This invention divides the heat shrink tubing inflation process into at least two stages. An intermediate heat treatment is added after the first inflation to release the internal stress accumulated in the tubing during the previous inflation. Then, a second inflation is performed until the target size is achieved. Compared to existing single-stage inflation methods, the heat shrink tubing prepared using this invention can significantly reduce the axial shrinkage rate while maintaining a high radial shrinkage rate. The heat-shrinked tubing has a smoother appearance, and the entire process requires no modification to the raw materials, thus not increasing raw material costs or process complexity. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic flowchart illustrating the method for preparing heat shrink tubing provided by the present invention.

[0019] Figure 2 This is a schematic diagram of the apparatus for preparing heat shrink tubing provided by the present invention.

[0020] Figure 3 A comparison diagram of heat shrink tubing expanded in stages and heat shrink tubing expanded in one stage.

[0021] In the diagram: 1. Traction module; 2. First heating module; 3. Second heating module; 4. Third heating module; 5. Moving platform; 6. Heat shrink tubing. Detailed Implementation

[0022] The invention will be more readily understood by referring to the following detailed description of preferred embodiments and included examples. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In case of conflict, the definitions in this specification shall prevail.

[0023] This invention provides a method and apparatus for preparing heat shrink tubing, which solves the problem that the existing technology of improving the heat shrinkability of heat shrink tubing by modifying raw materials not only increases costs but also makes the production process more cumbersome and complicated. Figure 1 This is a schematic diagram of the preparation method of the present invention. Figure 2 This is a schematic diagram of the preparation apparatus of the present invention. Figure 3 The images show a comparison of the appearance of heat shrink tubing prepared by the method of this invention and heat shrink tubing obtained by a single blow-up method.

[0024] Furthermore, to address this issue, some related technologies employ the method of inflating a base tube to a certain multiple in a single operation to prepare heat shrink tubing. However, heat shrink tubing prepared using this method exhibits an increased radial shrinkage rate as the axial shrinkage rate increases. (See reference...) Figure 3 The right image in the diagram greatly limits its application scenarios.

[0025] The inventive concept of this invention involves dividing the blowing process of heat shrink tubing into at least two stages. After the first blowing, an intermediate heat treatment step is added to release the internal stress accumulated in the tubing during the previous blowing. Then, a second blowing process is performed until the target size is achieved. Compared to existing single-stage blowing methods, this method significantly reduces the axial shrinkage rate while maintaining a high radial shrinkage rate. The heat-shrinked tubing has a smoother appearance, and the entire process requires no modification to the raw materials, thus not increasing raw material costs or process complexity.

[0026] like Figure 1 As shown, a method and apparatus for preparing a heat shrink tubing 6 includes: The initial heat shrink tubing 6 is first inflated, causing the radial dimension of the heat shrink tubing 6 to expand to the first intermediate dimension.

[0027] After cooling, the heat shrink tubing 6, which has undergone the first inflation, is subjected to intermediate heat treatment. The purpose of this heat treatment is to release the internal stress generated in the heat shrink tubing 6 during the first inflation process.

[0028] The heat shrink tubing 6, after undergoing intermediate heat treatment, is then inflated a second time to expand its radial dimension to the target final size.

[0029] Using the above method, the axial shrinkage rate of heat shrink tubing 6 can be effectively reduced without changing the raw materials, while maintaining a high radial shrinkage rate. The resulting appearance after heat shrinking is also smoother. Figure 3 As shown in the left figure. For example, using polyethylene terephthalate tubing as the initial tubing material, the heat shrink tubing 6 prepared by this method can achieve a heat shrinkage ratio of 2.0:1 at 200°C, while the single-blow inflation method can only achieve 1.6:1.

[0030] In one embodiment, when performing intermediate heat treatment on the heat shrink tubing 6 after the first inflation, the temperature of the intermediate heat treatment is controlled to be higher than the temperature during the first inflation, while being lower than the melting point or decomposition temperature of the initial heat shrink tubing 6 material. It is understood that at a temperature higher than the first inflation temperature, the molecular chains inside the tubing can obtain sufficient energy to relax, thereby releasing internal stress more fully, while avoiding excessively high temperatures that could cause the tubing to melt or decompose, thus ensuring the integrity of the product.

[0031] In one embodiment, the initial inflation ratio is controlled to be 50% to 80% of the target final inflation ratio. For example, if a final inflation ratio of 4.5 times is required, the initial inflation ratio is controlled between 2.25 and 3.6 times, preferably around 3 times. Using this range of step-by-step inflation allows for controllable deformation through the initial inflation while providing sufficient stretching space for the second inflation, resulting in a good balance between radial and axial shrinkage in the final product.

[0032] In one embodiment, the first and / or second inflation are performed at a temperature higher than the glass transition temperature of the initial heat shrink tubing material. Taking polyethylene terephthalate tubing as an example, its glass transition temperature is approximately 80°C. Therefore, the first inflation temperature can be set slightly above 80°C, and the second inflation temperature can be set to approximately the glass transition temperature +15°C, i.e., approximately 95°C. Inflation above the glass transition temperature allows the tubing to be in a highly elastic state, facilitating stretching and deformation, and resulting in better dimensional stability after deformation.

[0033] In one embodiment, after the first and / or second inflation, the inflated heat shrink tubing 6 is rapidly cooled and shaped. Specifically, this can be achieved by installing an air-cooling device at the outlet of the heating module and adjusting the compressed air flow rate within the range of 0-100 L / min, allowing the inflated heat shrink tubing 6 to rapidly cool below its glass transition temperature. Rapid cooling serves to promptly fix the inflated dimensions, preventing unnecessary shrinkage or deformation of the tubing due to residual heat, thereby ensuring the accuracy of the product dimensions.

[0034] On the other hand, such as Figure 2 As shown, the present invention also provides an apparatus for manufacturing heat shrink tubing 6, the apparatus comprising a traction module 1, a first heating module 2, a second heating module 3, a first sizing tube, and a second sizing tube. The traction module 1 is used to traction the heat shrink tubing 6 along a first direction, for example, the direction of tubing travel. The first heating module 2 and the second heating module 3 are arranged sequentially along the first direction. The first sizing tube is correspondingly arranged to the first heating module 2, and is used to constrain the heat shrink tubing 6, after a first inflation, to a first intermediate size. The second sizing tube is correspondingly arranged to the second heating module 3, and is used to constrain the heat shrink tubing 6, after a second inflation, to a target final size. The second heating module 3 is configured to perform intermediate heat treatment on the heat shrink tubing 6 after the treatment by the first heating module 2.

[0035] This device enables the continuous and efficient implementation of the aforementioned step-by-step inflation process, ensuring mass production of products.

[0036] In one embodiment, the apparatus further includes a third heating module 4 and a third sizing tube. The third heating module 4 is disposed after the second heating module 3 and is used to re-inflate or assist in shaping the heat shrink tubing 6. For example, when a higher inflation ratio or finer dimensional control is required, three heating modules can be used sequentially for the first inflation, intermediate heat treatment, second inflation, and even a third auxiliary shaping. The third sizing tube corresponds to the third heating module 4 to ensure the accuracy of the final dimensions.

[0037] In one embodiment, the temperatures of the first heating module 2 and the second heating module 3 are independently adjustable, and the adjustable temperature range of the second heating module 3 covers a temperature range higher than that of the first heating module 2. This independently adjustable design allows operators to flexibly set the heating temperature of each section according to the glass transition temperature and heat shrinkage performance requirements of different tubing materials. For example, for polyethylene terephthalate tubing, the temperature of the first heating module 2 can be set to 90°C and the temperature of the second heating module 3 to 120°C, thereby achieving a process sequence of first blowing and then heat treatment.

[0038] In one embodiment, the traction module 1 includes a movable platform 5 that can move along a first direction, a clamp for holding or pulling the heat shrink tubing 6, and a gas needle for filling the heat shrink tubing 6 with gas. The movable platform 5 drives the clamp forward at a set speed, and the gas needle passes through one end of the tubing and fills the tubing with nitrogen. Initially, one end of the heat shrink tubing 6 is knotted, and the other end passes through the heating module and is fixed by the clamp. After filling with nitrogen, the tubing remains sealed. This structure is simple and reliable, facilitating a stable inflation process on a continuous production line.

[0039] In one embodiment, the apparatus further includes a cooling device disposed at the outlet of the first heating module 2 and / or the second heating module 3. The cooling device is used to rapidly cool and shape the inflated heat shrink tubing 6. The cooling device can be an air-cooled nozzle, and the cooling rate is controlled by adjusting the flow rate of compressed air. Distributing the cooling device at the outlet of the first heating module 2 allows for rapid fixation of the intermediate dimensions after the first inflatation; distributing the cooling device at the outlet of the second heating module 3 allows for rapid fixation of the final product dimensions. Rapid cooling helps reduce axial shrinkage and improves the smoothness of the product's appearance.

[0040] In one embodiment, as shown in Table 1, polyethylene terephthalate pipe is used as the initial pipe material, with original pipe dimensions of 0.558 mm inner diameter and 0.889 mm outer diameter.

[0041] A step-by-step inflation process is adopted: The first step involves blowing the tube to approximately three times its original size at a temperature slightly above the glass transition temperature (approximately 85°C), thereby increasing the outer diameter of the tube to approximately 2.5 mm. Then, an intermediate heat treatment is performed at a temperature of approximately 100°C for a certain period of time to release internal stress, followed by cooling and shaping. The second step involves continuing to inflate the tube to its final size of 4.5 times its original size at a temperature 15°C above the glass transition temperature (approximately 95°C), resulting in an outer diameter of approximately 2.54 mm. The final heat shrink tubing 6 exhibits a heat shrinkage ratio of 2.0:1 at 200°C, with an axial shrinkage rate of only 26.4%.

[0042] For comparison, the heat-shrinkable tube 6 obtained by the single-blowing method (directly blowing the tube from 0.558 / 0.889mm to 2.54mm) has a heat shrinkage ratio of only 1.6:1 at 200℃, and the axial shrinkage rate is as high as 37.5%. Moreover, as Figure 3 shown in the figure, the sample subjected to stepwise blowing (left figure) shrinks smoothly on the mandrel with a flat appearance, while the sample subjected to single blowing (right figure) shows obvious wrinkles and unevenness on the surface.

[0043] Table 1 Comparison of heat shrinkage performance between stepwise blowing and single blowing

[0044] The heat-shrinkable tube 6 obtained by stepwise blowing is subjected to a heat shrinkage test at 120℃. At this time, the heat shrinkage ratio is 1.6:1, and the axial shrinkage rate is only 15.0%, which is far lower than 37.5% of the single-blowing sample at the same heat shrinkage ratio. This shows that by adopting the stepwise blowing method of the present invention, the same radial shrinkage effect can be achieved at a lower heat shrinkage temperature, and the axial shrinkage rate is greatly reduced, thereby broadening the application scenarios of the heat-shrinkable tube 6.

[0045] In one embodiment, the material of the initial heat-shrinkable tube 6 is not limited to polyethylene terephthalate, and may also be heat-shrinkable materials such as polyolefin and polyvinyl chloride. For different materials, it is only necessary to adjust the temperature parameters of each heating module and the blowing ratio according to their glass transition temperature and melting temperature, so that the stepwise blowing and intermediate heat treatment processes of the present invention can be applied to obtain the heat-shrinkable tube 6 with high radial shrinkage rate and low axial shrinkage rate.

[0046] In one embodiment, the inert gas filled during the blowing process may be nitrogen, argon or carbon dioxide, and the pressure value is adjustable within the range of 0-20bar. The traction speed is adjustable within the range of 0-10mm / s. The aperture of the sizing tube is selected according to the target size, and the aperture relationship of the three sizing tubes is R1<R2<R3. The temperature of the heating module is adjustable within the range of 0-500℃. The gas flow rate of air cooling is adjustable within the range of 0-100L / min. By adjusting the above parameters, the optimal process conditions can be found according to the actual production efficiency and product requirements.

[0047] Finally, it should be noted that the above descriptions are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still possible to modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall all be included in the protection scope of the present invention.

Claims

1. A method of producing a heat shrinkable tube, characterized by, include: The initial heat shrink tubing is first inflated, causing the radial dimension of the heat shrink tubing to expand to a first intermediate dimension; The heat shrink tubing is subjected to intermediate heat treatment after the first inflation to release the internal stress generated during the first inflation process. The heat shrink tubing, after undergoing intermediate heat treatment, is then inflated a second time to expand its radial dimension to the target final size.

2. The method of producing a heat shrinkable tube according to claim 1, characterized by, The intermediate heat treatment temperature is higher than the temperature of the first inflation, but lower than the melting point or decomposition temperature of the initial heat shrink tubing material.

3. The method of producing a heat shrinkable tube according to claim 1, characterized by, The first inflation ratio is 50% to 80% of the target final inflation ratio.

4. The method of producing a heat shrinkable tube according to claim 1, characterized by, The first and / or second inflation are performed under conditions higher than the glass transition temperature of the initial heat shrink tubing material.

5. The method of producing a heat shrinkable tube according to claim 1, wherein After the first and / or second inflation, the inflated heat shrink tubing is rapidly cooled and shaped.

6. The method for preparing heat shrink tubing according to claim 1, characterized in that, The initial heat shrink tubing is filled with inert gas of 0-20 bar during the inflation process, and the heat shrink tubing is pulled at a traction rate of 0-10 mm / s.

7. An apparatus for manufacturing heat shrink tubing, characterized in that, include: A traction module for pulling heat shrink tubing along a first direction; A first heating module and a second heating module are arranged sequentially along the first direction; A first sizing tube, corresponding to the first heating module, is used to limit the heat shrink tube, which has been inflated for the first time, to a first intermediate size. The second sizing tube, which is provided in accordance with the second heating module, is used to limit the heat shrink tube, which has been inflated a second time, to the target final size. The second heating module performs intermediate heat treatment on the heat shrink tubing that has been processed by the first heating module.

8. The apparatus for preparing heat shrink tubing according to claim 7, characterized in that, It also includes a third heating module and a third sizing tube. The third heating module is located after the second heating module and is used to re-inflate or assist in shaping the heat shrink tubing.

9. The apparatus for preparing heat shrink tubing according to claim 7, characterized in that, The temperatures of the first heating module and the second heating module are independently adjustable, and the adjustable temperature range of the second heating module covers a temperature range higher than that of the first heating module.

10. The apparatus for preparing heat shrink tubing according to claim 7, characterized in that, The traction module includes a movable platform that can move along the first direction, a clamp for holding or pulling the heat shrink tubing, and an air needle for filling the heat shrink tubing with gas.

11. The apparatus for preparing heat shrink tubing according to claim 7, characterized in that, It also includes a cooling device disposed at the outlet of the first heating module and / or the second heating module, the cooling device being used to rapidly cool and shape the inflated heat shrink tubing.

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