Heat shrinkable tube and its preparation method and application

Abstract

The application discloses a heat-shrinkable tube and a preparation method and application thereof. The heat-shrinkable tube comprises the following components in parts by weight: 40-60 parts of high-density polyethylene, 20-40 parts of medium-density polyethylene, 10-20 parts of elastomer and 0.1-0.5 parts of antioxidant. The heat-shrinkable tube provided by the application is excellent in rigidity and shrinkability and is non-toxic and harmless.

Description

Technical Field

[0001] This invention relates to the field of heat shrink tubing technology, specifically to a heat shrink tubing, its preparation method, and its applications. Background Technology

[0002] Heat shrink tubing shrinks (i.e., its diameter decreases) when heated to a given temperature. This allows it to provide a tight-fitting protective sleeve for the close coverage and isolation of various components; it can be used to wrap components together (i.e., within the same heat shrink tubing); it can be used to connect / fuse two components (e.g., two tubes) together; and it can be used to modify the properties of the wrapped material (e.g., by surrounding another material and causing it to shrink as well). These capabilities make heat shrink tubing widely used in the medical, chemical, electrical, optical, electronic, aerospace, automotive, and communications fields.

[0003] In the field of medical devices, heat shrink tubing is particularly advantageous for use with delicate devices inserted into the body, such as catheters and endoscopes. A representative medical application of heat shrink tubing is in the manufacture of guide catheters, which consist of a tubular structure with a polymer inner layer, a wire braided middle layer, and another polymer outer layer. To assemble such a catheter, an expanded heat shrink tubing is typically applied to the assembly sleeve around a mandrel, exposing the assembly to high temperatures sufficient to cause the heat shrink tubing to shrink. Under these conditions, the outer polymer layer within the catheter sleeve melts and flows, and the heat shrink tubing shrinks, providing pressure that allows the inner and outer polymer layers of the catheter sleeve to bond together, thereby encapsulating the wire braided structure. This requires the heat shrink tubing to have high shrinkage force, a shrinkage temperature above the melting temperature of the shrink element, and to be non-toxic and harmless to the human body. Polyethylene is widely used in the manufacture of heat shrink tubing for medical catheters due to its advantages such as corrosion resistance, good processability, non-toxicity, odorlessness, and low cost. High-density polyethylene (HDPE) also has a high modulus, and its rigidity makes it easy to insert conduits and mandrels.

[0004] However, unmodified polyethylene has poor temperature resistance and insufficient melt strength. Crosslinking modification is an effective method to construct a three-dimensional entangled network structure between macromolecular chains, thereby improving the melt strength, thermal stability, and shrinkage of the material. Currently, crosslinked polyethylene mainly includes peroxide crosslinking, radiation crosslinking, and silane crosslinking. Peroxide and silane crosslinking require the addition of chemical crosslinking agents and other additives to the formulation, and these additives are harmful to the human body. Radiation crosslinking, on the other hand, does not require the addition of initiators or other additives to initiate crosslinking or grafting reactions, is pollution-free, and is easy to process. However, due to its high crystallinity, HDPE has limited irradiation crosslinking degree while maintaining its rigidity and pollution-free properties, resulting in insufficient shrinkage force of HDPE heat shrink tubing, making it difficult to meet the high requirements of medical applications. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the present invention proposes a heat shrink tubing, its preparation method and application. The heat shrink tubing has high rigidity, and the guide tube and mandrel are easy to insert into it, making it convenient to use. It has a fast shrinking speed, high shrinkage rate and large shrinking force, which can make the internal shrinkable parts tightly connected without air bubbles and not stick to the surface of the shrinkable parts. It has high temperature resistance, is non-toxic and harmless, low price and high transparency.

[0006] To achieve the above objectives, the present invention provides a heat shrink tubing, wherein the ingredients of the heat shrink tubing, by weight, include: 40-60 parts of high-density polyethylene, 20-40 parts of medium-density polyethylene, and 10-20 parts of elastomer.

[0007] Optionally, the melt index of the high-density polyethylene is 0.35 g / min to 10 g / min; and / or, the melt index of the medium-density polyethylene is 0.35 g / min to 10 g / min.

[0008] Optionally, the high-density polyethylene has a melting temperature greater than 130°C; and / or, the medium-density polyethylene has a melting temperature of 115°C to 125°C.

[0009] Optionally, the elastomer comprises polybutadiene and / or SBS; and / or further comprises 0.1-0.5 parts of an antioxidant, said antioxidant comprising hindered phenolic antioxidants.

[0010] To achieve the above objectives, the present invention also proposes a method for preparing the above-mentioned heat shrink tubing, comprising the following steps: mixing high-density polyethylene, medium-density polyethylene and elastomer to obtain a mixture; adding the mixture to a twin-screw extruder for granulation, cutting and drying to obtain granulated material; adding the granulated material to a single-screw extruder for extrusion to obtain an extruded tube; and irradiating and expanding the extruded tube to obtain a heat shrink tubing.

[0011] Optionally, the mixing includes mixing high-density polyethylene, medium-density polyethylene, elastomer and antioxidant; and / or, the mixing temperature is 165°C to 175°C; and / or, the mixing time is 8 min to 15 min.

[0012] Optionally, the irradiation is performed using an electron accelerator; and / or, the irradiation temperature is 85°C to 95°C; and / or, the irradiation dose is 50 kGy to 70 kGy.

[0013] Optionally, the expansion molding is performed using an internal pressure blow molding method; and / or, the expansion molding temperature is 115℃~125℃.

[0014] To achieve the above objectives, the present invention also proposes an application of the heat shrink tubing, including applying the heat shrink tubing to medical devices.

[0015] The beneficial effects of this invention are as follows: High-density polyethylene (HDPE) has high crystallinity and high modulus, making it easy to insert rigid heat-shrink tubing into medical catheters and mandrels. During irradiation crosslinking, crosslinking mainly occurs in the amorphous region. When HDPE is irradiated and crosslinked to a certain extent, the movement of macromolecular chain segments in the amorphous region is hindered. Even if there are still many free radicals on the molecular chain, it is difficult to further react and crosslink, which may lead to molecular chain degradation. Therefore, it is difficult to obtain a high degree of crosslinking through higher irradiation doses. To further improve the resilience, medium-density polyethylene (MDPE) is introduced. MPE itself maintains the rigidity of HDPE, and its crystalline region melting temperature is lower than that of HDPE. Utilizing this characteristic, the crystalline region melting temperature of the system is designed to further improve the resilience. Expansion occurs near the melting temperature of MPE. At this point, the elastomer component, most of the crystalline regions of MPE, and a small number of crystalline regions of HDPE are in a molten state. The entire material becomes a highly elastic state that can undergo large deformation under external force. Most of the crystalline regions of HDPE can act as physical crosslinking points, which is equivalent to improving the crosslinking structure of the entire system.

[0016] In the above system, the elastomer, as the dispersed phase, is mainly dispersed in the amorphous region of the polyethylene continuous phase, forming a sea-island structure inside. Through irradiation, the elastomer molecular chains and polyethylene molecular chains at the interface of the two phases undergo an interfacial grafting reaction, and the amorphous and crystalline regions interpenetrate with each other to form a stable interface, ensuring effective stress transfer between the entire system.

[0017] This invention eliminates the need for irradiation additives. By compounding high-density polyethylene, medium-density polyethylene, and elastomers, heat shrink tubing with high rigidity, fast shrinkage speed, high shrinkage rate, and high shrinkage force can be prepared without adhering to the surface of the shrinkable part. It also has the advantages of high temperature resistance, non-toxicity, low price, and high transparency, making it suitable for the medical field. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. It should be understood that the following embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0019] Unless otherwise specified, all technical and scientific terms used herein have their usual meaning within the field to which the subject matter is claimed.

[0020] In the field of medical devices, heat shrink tubing is particularly advantageous for use with delicate devices inserted into the body, such as catheters and endoscopes. A representative medical application of heat shrink tubing is in the manufacture of guide catheters, which consist of a tubular structure having a polymer inner layer, a wire braided middle layer, and a polymer outer layer. To assemble such a catheter, expanded heat shrink tubing is typically applied to the tubular structure, which is fitted over the outer wall of a mandrel, and the assembly is exposed to high temperatures sufficient to cause the heat shrink tubing to shrink. Under these conditions, the polymer outer layer of the tubular structure melts and flows, and the heat shrink tubing shrinks, providing pressure that allows the polymer outer and inner layers of the tubular structure to bond together, thereby encapsulating the wire braided structure. This requires the heat shrink tubing to have high shrinkage force, a shrinkage temperature above the melting temperature of the shrinkable component, and to be non-toxic and harmless to the human body.

[0021] However, HDPE has a high degree of crystallinity, while radiation cross-linking mainly occurs in the amorphous region, resulting in insufficient shrinkage force of pure HDPE heat shrink tubing, which makes it difficult to meet the high requirements of medical applications.

[0022] To address the above problems, this invention proposes a heat shrink tubing, wherein the materials of the heat shrink tubing, by weight, include: 40-60 parts of high-density polyethylene, 20-40 parts of medium-density polyethylene, and 10-20 parts of elastomer.

[0023] Polyethylene (PE) offers advantages in manufacturing medical catheters, including corrosion resistance, good processability, non-toxicity, odorlessness, and low cost. High-density polyethylene (HDPE), with its high crystallinity and high modulus, facilitates the insertion of catheters and mandrels into rigid heat-shrink tubing. However, during irradiation crosslinking, crosslinking primarily occurs in the amorphous regions. The degree of crosslinking in HDPE is insufficient to meet the required shrinkage force. Therefore, medium-density polyethylene (MDPE) to high-density polyethylene (HDPE) is added, along with an elastomer to modify the polyethylene. In this system, the elastomer acts as the dispersed phase, primarily dispersed in the amorphous regions of the continuous polyethylene phase, forming an island-sea structure. Through irradiation, the elastomer molecular chains at the interface between the two phases undergo interfacial grafting reactions with the polyethylene molecular chains. Furthermore, the amorphous and crystalline regions interpenetrate, forming a stable interface that ensures effective stress transfer throughout the system. In this design, the heat-shrink tubing meets the required mechanical and shrinkage properties without the addition of low-molecular-weight irradiation additives.

[0024] In some embodiments, the elastomer is in the form of 10 parts, 12 parts, 14 parts, 16 parts, 18 parts, or 20 parts.

[0025] In some embodiments, the high-density polyethylene is in the form of 40 parts, 45 parts, 50 parts, 55 parts, or 60 parts.

[0026] In some embodiments, the medium-density polyethylene is in the form of 20 parts, 25 parts, 30 parts, 35 parts, or 40 parts.

[0027] In this scheme, medium-density polyethylene (MDPE) maintains the rigidity of HDPE, but its crystalline melting temperature is lower than that of HDPE. Taking advantage of this characteristic, the crystalline melting temperature of the MDPE design system is introduced into HDPE. Combined with a specific expansion process, the crystalline region can be used to further improve the resilience of the heat shrink tubing.

[0028] Further, the melt index of the high-density polyethylene is 0.35 g / 10 min to 10 g / 10 min; and / or, the melt index of the medium-density polyethylene is 0.35 g / 10 min to 10 g / 10 min. The melt index is the amount of thermoplastic material extruded under specified conditions within a certain time, used to characterize the viscous flow characteristics of thermoplastics in the molten state. A melt index within this range is beneficial for accurately controlling the preparation process.

[0029] In some embodiments, the melt index of high-density polyethylene is 0.5 g / 10 min, 1 g / 10 min, 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, or 9.5 g / 10 min.

[0030] In some embodiments, the melt index of medium-density polyethylene is 0.5 g / 10 min, 1 g / 10 min, 1.5 g / 10 min, 2 g / 10 min, 2.5 g / 10 min, 3 g / 10 min, 3.5 g / 10 min, 4 g / 10 min, 4.5 g / 10 min, 5 g / 10 min, 5.5 g / 10 min, 6 g / 10 min, 6.5 g / 10 min, 7 g / 10 min, 7.5 g / 10 min, 8 g / 10 min, 8.5 g / 10 min, 9 g / 10 min, or 9.5 g / 10 min.

[0031] Further, the high-density polyethylene has a melt temperature greater than 130°C; and / or, the medium-density polyethylene has a melt temperature of 115°C to 125°C. Designing the melt temperature facilitates the integration with specific expansion processes, utilizing crystalline regions to further enhance resilience. In some embodiments, the melt temperature of high-density polyethylene is 130°C, 135°C, or 138°C. In some embodiments, the melt temperature of medium-density polyethylene is 118°C, 120°C, or 123°C.

[0032] Further, the elastomer comprises polybutadiene and / or SBS; and / or, further comprises 0.1-0.5 parts of an antioxidant, wherein the antioxidant comprises a hindered phenolic antioxidant. Polybutadiene (PB) has the advantages of high elasticity, aging resistance, and low cost. SBS is a triblock copolymer with styrene and butadiene as monomers. After cooling to room temperature, the polystyrene segments aggregate into glassy microdomains, which crosslink the polybutadiene segments, resulting in excellent elastomer performance. In some embodiments, the antioxidant includes antioxidant 1010 and / or antioxidant 1098.

[0033] In this solution, the components used in the heat shrink tubing are all non-polar polymers, while the polymers that need to be fused inside medical catheters are often polar nylon materials. After shrinking, the heat shrink tubing does not stick to the shrinkable part and does not damage the surface of the shrinkable part.

[0034] To address the above problems, the present invention also proposes a method for preparing the aforementioned heat shrink tubing, comprising the following steps:

[0035] S1: High-density polyethylene, medium-density polyethylene, and elastomer are mixed to obtain a mixture;

[0036] In one embodiment, high-density polyethylene, medium-density polyethylene, and elastomer are added to a mixer in a preset ratio and mixed to uniformly disperse the medium-density polyethylene and elastomer in the high-density polyethylene, thereby obtaining a mixture.

[0037] S2: The mixture is added to a twin-screw extruder for granulation, cutting, and drying to obtain granulated material;

[0038] In one embodiment, the mixture is introduced into a twin-screw extruder for further mixing and granulation to ensure that the components are fully and uniformly mixed. The temperature of the feeding section of the twin-screw extruder is 130-160°C, the temperature of the compression section is 170-180°C, the temperature of the homogenization section is 180-190°C, and the screw speed is 130-150 r / min. After being cut into appropriate granules by a pelletizer, the granules are dried at 80°C for 6-15 hours to obtain the granulated material.

[0039] S3: The granulated material is added to a single-screw extruder and extruded to obtain an extruded tube;

[0040] In one embodiment, the granulated material is extruded through a single-screw extruder to form an extrusion tube of the desired size.

[0041] S4: Irradiate and expand the extruded tube to obtain a heat shrink tube.

[0042] In one embodiment, the extruded tube is irradiated at a preset temperature, which improves the mobility of the elastomer components and amorphous molecular chains, and makes it easier for macromolecular free radicals to combine and generate cross-links, so that a fully cross-linked network structure is formed inside the extruded tube. After expansion and rapid cooling, a large amount of stress is stored inside the tube as shrinkage force after heating.

[0043] Further, the mixing includes mixing high-density polyethylene, medium-density polyethylene, elastomer and antioxidant; and / or, the mixing temperature is 165°C to 175°C; and / or, the mixing time is 8 min to 15 min.

[0044] Within the specified mixing temperature and time range, the mixture can be guaranteed to be evenly dispersed.

[0045] Furthermore, the irradiation is performed using an electron accelerator; and / or, the irradiation temperature is 85°C to 95°C; and / or, the irradiation dose is 50 kGy to 70 kGy. Electron accelerator irradiation processing utilizes a high-energy electron beam to bombard the interior of the product, causing the molecular structure to rearrange and altering the crosslinking properties of the extruded tube. Within the aforementioned irradiation temperature range, the efficiency of irradiation crosslinking can be improved. Within the aforementioned irradiation dose range, effective crosslinking can be achieved.

[0046] Furthermore, the expansion molding employs an internal pressure blowing method; and / or, the expansion molding temperature is 115℃~125℃. Since the melting temperature of high-density polyethylene is above 130℃ and that of medium-density polyethylene is approximately 120℃, during expansion at 115℃~125℃, the elastomer component, amorphous regions, most of the crystalline regions of medium-density polyethylene, and a small number of crystalline regions of high-density polyethylene are all in a molten state. The entire material becomes a highly elastic state capable of large deformation under external force, manifested as a high expansion ratio. Most of the crystalline regions of high-density polyethylene can act as physical cross-linking points, effectively improving the cross-linking structure of the entire system. Under the blowing force, the cross-linked network structure and unmelted crystalline regions are forced to expand and deform. Rapid cooling causes a large amount of stress to be stored inside the pipe. When reheated, the stress in the cross-linked network structure and the expanded unmelted crystalline regions is released, and the stable internal interface ensures effective stress transfer between the entire system, thereby providing effective recovery force. Consequently, the pipe exhibits large shrinkage force and shrinkage rate.

[0047] To achieve the above objectives, the present invention also proposes an application of the heat shrink tubing, including its application in medical devices. In one embodiment, the medical device is a medical catheter, and the polymer to be fused inside the medical catheter is often made of nylon, thus often requiring shrinkage at temperatures above 220°C. By effectively improving the cross-linked network structure of the heat shrink tubing system, increasing the degree of entanglement between the molecular chains of the heat shrink tubing, the melt strength of the material is improved, thereby enhancing the heat resistance of the heat shrink tubing.

[0048] Example 1:

[0049] Raw materials: By weight percentage, the ingredients for high-rigidity, high-shrinkage HDPE heat shrink tubing include: 59.9 parts HDPE, 20 parts MDPE, 20 parts SBS, and 0.1 parts antioxidant 1010. The HDPE has a melting temperature of approximately 138℃, a melt index of 0.36 g / 10 min, and a density of 0.965 g / cm³. 3 MDPE has a melting temperature of approximately 123℃, a melt index of 10 g / 10 min, and a density of 0.930 g / cm³. 3 .

[0050] Preparation: Weighed HDPE, MDPE, SBS, and antioxidant 1010 are mixed evenly in a mixer at 175℃ for 8 minutes, then crushed into granules. The crushed material is then fed into a twin-screw extruder for further mixing and granulation, and cut into appropriate granules by a pelletizer before drying. The granulated material is extruded into pipes of the required size using a single-screw extruder. The extruded pipes are irradiated using an electron accelerator at 95℃ and a dose of 50 kGy. Finally, the irradiated pipes are expanded and molded using an internal pressure blowing method at 125℃ to obtain heat-shrink tubing.

[0051] Example 2:

[0052] The preparation method is the same as in Example 1, except that:

[0053] The raw materials include 49.5 parts HDPE, 40 parts MDPE, 10 parts polybutadiene, and 0.5 parts antioxidant 1098. The HDPE has a melt temperature of 135℃, a melt index of 4 g / 10 min, and a density of 0.958 g / cm³. 3 MDPE has a melting temperature of 120℃, a melt index of 5 g / 10 min, and a density of 0.933 g / cm³. 3 .

[0054] The mixing temperature is 170℃, and after mixing for 12 minutes, it is crushed into granules.

[0055] The irradiation temperature was 90℃ and the dose was 60kGy.

[0056] The expansion temperature is 120℃, resulting in heat shrink tubing.

[0057] Example 3:

[0058] The preparation method is the same as in Example 1, except that:

[0059] The raw materials include 40 parts HDPE, 39.7 parts MDPE, 10 parts SBS, 10 parts polybutadiene, 0.1 parts antioxidant 1010, and 0.2 parts antioxidant 1098. The HDPE has a melting temperature of 130℃, a melt index of 10 g / 10 min, and a density of 0.951 g / cm³. 3 MDPE has a melting temperature of 118℃, a melt index of 0.35 g / 10 min, and a density of 0.940 g / cm³. 3 .

[0060] The mixing temperature is 165℃, and after mixing for 15 minutes, it is crushed into granules.

[0061] The irradiation temperature was 85℃ and the dose was 70kGy.

[0062] The expansion temperature is 115℃, resulting in a heat shrink tubing.

[0063] Example 4:

[0064] The difference from Example 3 is as follows:

[0065] The raw materials include 45 parts HDPE, 35 parts MDPE, 19.7 parts polybutadiene, and 0.3 parts antioxidant 1010.

[0066] The irradiation dose was 65 kGy.

[0067] The expansion temperature is 120℃.

[0068] Example 5:

[0069] The difference from Example 3 is as follows:

[0070] The raw materials include 60 parts HDPE, 20 parts MDPE, 19.5 parts polybutadiene, and 0.5 parts antioxidant 1010.

[0071] The irradiation temperature was 95℃ and the dose was 68kGy.

[0072] The expansion temperature is 120℃.

[0073] Comparative Example 1:

[0074] The difference from Example 1 is as follows:

[0075] The raw materials include 79.9 parts HDPE, 20 parts SBS, and 0.1 parts antioxidant 1010.

[0076] The expansion temperature is approximately 138℃.

[0077] Comparative Example 2:

[0078] The difference from Example 1 is as follows:

[0079] The raw materials include 79.9 parts MDPE, 20 parts SBS, and 0.1 parts antioxidant 1010.

[0080] Comparative Example 3:

[0081] The difference from Example 1 is as follows:

[0082] The raw materials include 30 parts HDPE, 49.9 parts MDPE, 20 parts SBS, and 0.1 parts antioxidant 1010.

[0083] Comparative Example 4:

[0084] The difference from Example 1 is as follows:

[0085] The raw materials include 50 parts HDPE, 49.9 parts MDPE, and 0.1 parts antioxidant 1010.

[0086] The components and key preparation variables of the examples and comparative examples are summarized in Table 1.

[0087] Table 1.

[0088]

[0089]

[0090] The heat shrink tubing in Examples 1-5 and Comparative Examples 1-4 were tested for secant modulus, degree of crosslinking, shrinkage performance, shape fixation rate, and shape recovery rate. The test methods used are as follows:

[0091] 1. Secant modulus test

[0092] Using the tensile testing mode of a tensile testing machine, and in accordance with UL 224 standard, unshrinked heat shrink tubing was used to cut 300mm specimens for secant modulus testing. The clamping distance was 254mm, the clamping tensile speed was 25.4mm / min, and the test temperature was 25℃.

[0093] 2. Crosslinking degree test

[0094] Weigh a certain amount of crosslinked material fragments, wrap them in a 120-mesh copper mesh, and then place them in an Erlenmeyer flask equipped with a reflux device. Using xylene as a solvent, boil and reflux for 24 hours, then dry to constant weight. Calculate the gel content and use the gel content to indirectly measure the degree of crosslinking.

[0095] 3. Shrinkage performance test

[0096] Take the mandrel and the nylon tubing, put the nylon tubing on the mandrel, and shrink it using the HDPE heat shrink tubing described in this invention. Observe whether the nylon tubing can be evenly fused and wrapped on the mandrel, and observe the appearance of the fused nylon tubing.

[0097] 4. Shape fixation rate and shape recovery rate test

[0098] The inner diameter of the pipe after extrusion is recorded as I0, the inner diameter after expansion is recorded as I1, the inner diameter after the expanded pipe is placed at room temperature for 24 hours is recorded as I2, and the inner diameter after the expanded pipe is heated and shrunk again is recorded as I3. The shape fixation rate (SF) and shape recovery rate (SR) are calculated as follows: SF = (I2-I0) / (I1-I0), SR = (I2-I3) / (I2-I0).

[0099] The test results are recorded in Table 2 below:

[0100] Table 2. Performance of Examples 1-5 and Comparative Examples 1-4 of the present invention

[0101]

[0102]

[0103] As can be seen from the test results above, the heat shrink tubing in Examples 1-5 all meet the rigidity requirements for use. Without adding other irradiation additives, the degree of cross-linking exceeds the application requirements of cross-linked polyethylene materials, and the shrinkage performance also meets the performance requirements of heat shrink tubing for high-demand medical device applications. Compared to the comparative example, the shrinkage and recovery rate can reach 100%, verifying that the heat shrink tubing provided by this invention has high rigidity, making it easy to insert conduits and mandrels; it shrinks quickly after heating, has a high shrinkage rate and large shrinkage force, ensuring a tight connection of internal shrinkable components without air bubbles and preventing adhesion to the surface of the shrinkable components; it also has many advantages such as high temperature resistance, non-toxicity, low price, and high transparency, making it suitable for the medical field.

[0104] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the patent protection scope of the present invention.

Claims

1. A heat shrink tubing, characterized in that, The ingredients of the heat shrink tubing, by weight, include: 40-60 parts of high-density polyethylene 20-40 parts of medium-density polyethylene 10-20 parts of elastomer; The elastomer includes polybutadiene and / or SBS; The high-density polyethylene has a melting temperature greater than 130°C, and the medium-density polyethylene has a melting temperature of 115°C to 125°C. The high-density polyethylene, medium-density polyethylene, and elastomer are compounded, granulated, and extruded to obtain an extruded tube. The extruded tube is then irradiated and expanded to obtain a heat-shrinkable tube. The expansion temperature is 115℃~125℃.

2. The heat shrink tubing as described in claim 1, characterized in that, The melt flow index of the high-density polyethylene is 0.35 g / min to 10 g / min; And / or, the melt index of the medium-density polyethylene is 0.35 g / min to 10 g / min.

3. The heat shrink tubing as described in claim 1, characterized in that, The elastomer further includes 0.1-0.5 parts of an antioxidant, which includes hindered phenolic antioxidants.

4. A method for preparing a heat shrink tubing as described in claim 1, characterized in that, Includes the following steps: High-density polyethylene, medium-density polyethylene and elastomer are mixed to obtain a mixture; The mixture is added to a twin-screw extruder for granulation, cutting, and drying to obtain granulated material. The granulated material is added to a single-screw extruder and extruded to obtain an extruded tube; The extruded tube is irradiated and expanded to obtain a heat shrink tube.

5. The method for preparing heat shrink tubing as described in claim 4, characterized in that, The compounding process includes compounding high-density polyethylene, medium-density polyethylene, elastomers and antioxidants; And / or, the mixing temperature is 165℃~175℃; And / or, the mixing time is 8 min to 15 min.

6. The method for preparing heat shrink tubing as described in claim 4, characterized in that, The irradiation was carried out using an electron accelerator; And / or, the irradiation temperature is 85°C to 95°C; And / or, the irradiation dose is 50 kGy to 70 kGy.

7. The method for preparing heat shrink tubing as described in claim 4, characterized in that, The expansion molding process employs an internal pressure blowing method. And / or, the expansion molding temperature is 115℃~125℃.

8. An application of the heat shrink tubing as described in any one of claims 1 to 3, characterized in that, This includes applying the heat shrink tubing to medical devices.

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