Medical heat shrink tubing and preparation method thereof

Abstract

The present invention provides a medical heat shrink tubing and a preparation method thereof. The heat shrink tubing is composed of the following components by mass percentage: 65% to 95% polyethylene, 3% to 30% toughening agent, and 0.5% to 5% antioxidant. The preparation method comprises: extruding a premix from an extruder and granulating it to form a masterbatch; the premix is ​​mixed with the following components by mass percentage: 65% to 95% polyethylene, 3% to 30% toughening agent, and 0.5% to 5% antioxidant; extruding the masterbatch through an extruder and cooling it to obtain a raw tubing; irradiating the raw tubing multiple times using a high-energy electron accelerator under vacuum conditions to obtain a semi-finished tubing; adjusting the relative orientation of the high-energy electron accelerator and the raw tubing before each irradiation; and sizing and expanding the semi-finished tubing to obtain the heat shrink tubing. The heat shrink tubing is easy to thread and also has good thermal stability, oxidation resistance, and tearability.

Description

Technical Field

[0001] The present invention relates to the technical field of medical tube preparation, and in particular to a medical heat shrink tube and a preparation method thereof. Background Art

[0002] Heat shrink tubing, also known as heat shrink tubing, is widely used in aviation, aerospace, automotive, home appliances, communications, petrochemicals, and other fields. In recent years, with the continued rapid development of the medical industry, medical heat shrink tubing has also emerged. Medical heat shrink tubing can provide friction protection for medical devices, insulation for laparoscopic electrosurgical equipment, mechanical protection and insulation for highly flexible joints, and auxiliary processes for interventional applications.

[0003] In the production process of medical devices, it is often necessary to weld two or more pipes of different materials together. Direct welding can easily cause solder joint displacement, miswelding or over-welding. In this case, you can consider using heat shrink tubing for auxiliary welding, using heat shrink tubing for positioning and protecting the solder joints. When using transparent heat shrink tubing, it is also helpful to observe the solder joints. After welding is completed, you only need to peel off the shrunken heat shrink tubing. This requires that the heat shrink tubing should not only be easy to thread the tube, but also have good thermal stability, oxidation resistance, and tearability. However, the heat shrink tubing in the prior art is difficult to meet the above requirements. Summary of the Invention

[0004] The purpose of the present invention is to provide a medical heat shrinkable tube and a preparation method thereof, aiming to improve the performance of the medical heat shrinkable tube, make it easy to wear the tube, and also have good thermal stability, oxidation resistance and tearability.

[0005] To achieve the above-mentioned object, the present invention provides a heat shrinkable tube, which is composed of the following components by mass percentage: 65% to 95% of polyethylene, 3% to 30% of a toughening agent, and 0.5% to 5% of an antioxidant; the toughening agent includes at least one of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer.

[0006] Optionally, the polyethylene includes at least one of linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

[0007] Optionally, the polyethylene has a melt index of 1 g / 10 min to 5 g / 10 min.

[0008] Optionally, the melt index of the toughening agent is 0.5 g / 10 min to 5 g / 10 min.

[0009] Optionally, the antioxidant includes at least one of 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, dioctadecyl thiodipropionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, didodecyl thiodipropionate, tris[2.4-di-tert-butylphenyl]phosphite, and dibutylhydroxytoluene.

[0010] To achieve the above object, the present invention also provides a method for preparing a medical heat shrink tubing, the method comprising the following steps:

[0011] The premix is ​​extruded from an extruder and granulated to form a masterbatch; the premix is ​​composed of the following components in percentage by mass: 65% to 95% of polyethylene, 3% to 30% of a toughening agent, and 0.5% to 5% of an antioxidant; wherein the toughening agent comprises at least one of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer;

[0012] Extruding the masterbatch and cooling it to obtain a green tube;

[0013] Under vacuum conditions, the raw tube is irradiated multiple times using a high-energy electron accelerator to obtain a semi-finished tube; before each irradiation, the relative position of the high-energy electron accelerator and the raw tube is adjusted; and

[0014] The semi-finished pipe is expanded to obtain a heat shrinkable tube.

[0015] Optionally, the premix is ​​extruded and granulated using a twin-screw extruder, wherein the heating temperature of the twin-screw extruder is 270°F to 400°F; and / or,

[0016] The masterbatch is extruded through a single-screw extruder to obtain the green pipe, and the heating temperature of the single-screw extruder is 330°F to 400°F.

[0017] Optionally, the masterbatch is immersed in a cooling liquid for cooling after extrusion, and the temperature of the cooling liquid is 3°C to 5°C.

[0018] Optionally, the energy of the high-energy electron accelerator is 5 MeV to 10 MeV, and the dose during each irradiation is 15 kGy to 60 kGy, and the total dose of multiple irradiations is 400 kGy to 800 kGy.

[0019] Optionally, the primary tube is wound into a disk and has a first end face and a second end face relative to each other in the axial direction; adjusting the relative orientation of the high-energy electron accelerator and the primary tube before each irradiation means that during the last irradiation, one of the first end face and the second end face faces the high-energy electron accelerator, and before the next irradiation, the primary tube is flipped 180° so that the other of the first end face and the second end face faces the high-energy electron accelerator.

[0020] Optionally, the step of sizing and expanding the semi-finished tube includes: heating the semi-finished tube to soften the semi-finished tube, then introducing gas into the inner cavity of the semi-finished tube so that the radial dimension of the semi-finished tube increases under the action of the gas pressure, and finally cooling to obtain the heat shrink tube.

[0021] Compared with the prior art, the medical heat shrink tubing and its preparation method of the present invention have the following advantages:

[0022] The aforementioned medical heat shrink tubing is composed of the following components, measured by mass: 65% to 95% polyethylene, 3% to 30% toughening agent, and 0.5% to 5% antioxidant. The toughening agent includes at least one of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer. Polyethylene, as the primary substrate, has a semi-crystalline structure that easily crosslinks with the toughening agent and antioxidant to form a network structure, which improves the mechanical properties of the heat shrink tubing and facilitates pipe threading. The use of a toughening agent enhances the overall crystallinity of the heat shrink tubing material and increases the compatibility of its components, resulting in excellent resilience and tearability. The present invention uses minimal antioxidant. By selecting an appropriate antioxidant, the introduction of colored substances can be minimized while maintaining the heat shrink tubing's antioxidant properties, thereby maximizing transparency and facilitating weld observation during pipe welding.

[0023] The aforementioned method for preparing a medical heat shrink tubing comprises the following steps: extruding a premix from an extruder and granulating it to form a masterbatch; the premix is ​​composed of a mixture of the following components by mass percentage: 65% to 95% polyethylene, 3% to 30% toughening agent, and 0.5% to 5% antioxidant; extruding the masterbatch through an extruder and cooling it to obtain a nascent tubing; irradiating the nascent tubing multiple times using a high-energy electron accelerator under vacuum conditions to obtain a semi-finished tubing; adjusting the relative orientation of the high-energy electron accelerator and the nascent tubing before each irradiation; and sizing and expanding the semi-finished tubing to obtain a heat shrink tubing. In this preparation method, by improving the formula and performing multiple irradiations using a high-energy electron accelerator, and changing the relative orientation of the high-energy electron accelerator and the primary tube during each irradiation, irradiation uniformity can be improved, avoiding local softening, adhesion, and agglomeration of the heat shrink tubing caused by excessively rapid heat release from components during a cross-linking reaction, thereby improving the uniformity of the performance of the medical heat shrink tubing. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are provided for a better understanding of the present invention and are not intended to limit the present invention.

[0025] Figure 1 The present invention is a flowchart of a method for preparing a heat shrink tube according to one embodiment of the present invention. DETAILED DESCRIPTION

[0026] The following describes the embodiments of the present invention through specific specific examples. Those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in this embodiment only illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components during actual implementation. During actual implementation, the type, quantity and proportion of each component can be changed at will, and the component layout type may also be more complicated.

[0027] In addition, each embodiment described below has one or more technical features. However, this does not mean that users of the present invention must implement all technical features in any embodiment at the same time, or that they can only implement some or all technical features in different embodiments separately. In other words, as long as implementation is possible, those skilled in the art can, based on the disclosure of the present invention and depending on design specifications or implementation requirements, selectively implement some or all technical features in any embodiment, or selectively implement a combination of some or all technical features in multiple embodiments, thereby increasing the flexibility of the implementation of the present invention.

[0028] As used in this specification, the singular forms "a," "an," and "the" include plural referents, and the plural form "a plurality" includes more than two referents, unless the context clearly indicates otherwise. As used in this specification, the term "or" is generally used in a sense including "and / or," unless the context clearly indicates otherwise. Those skilled in the art will understand the specific meanings of these terms in the present invention based on specific circumstances.

[0029] In order to make the objects, advantages and features of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings.

[0030] The heat shrink tubing provided in one embodiment of the present invention is composed of the following components by mass percentage: 65% to 95% polyethylene, 3% to 30% toughening agent, and 0.5% to 5% antioxidant. Figure 1 As shown, the preparation method of the medical heat shrink tube may include the following steps:

[0031] Step S1: Extruding the premix from an extruder and pelletizing it to form a masterbatch. The premix herein is composed of the following components by mass percentage: 65% to 95% polyethylene, 3% to 30% toughening agent, and 0.5% to 5% antioxidant.

[0032] Step S2: Extruding the masterbatch through an extruder and cooling it to obtain a raw pipe.

[0033] Step S3: Under vacuum conditions, the raw tube is irradiated multiple times using a high-energy electron accelerator to obtain a semi-finished tube. Before each irradiation, the relative position of the high-energy electron accelerator and the raw tube is adjusted. And,

[0034] Step S4: performing diametric expansion on the semi-finished tube to obtain the medical heat shrink tube.

[0035] The premix can be obtained by mixing the polyethylene, the toughening agent, and the antioxidant in a predetermined ratio in any suitable manner in step S0. Step S0 is performed before step S1. In an optional implementation, the polyethylene, the toughening agent, and the antioxidant are mixed in a high-speed blender to form the premix.

[0036] The medical heat shrink tubing and preparation method thereof provided in the embodiment of the present invention use polyethylene as the main base material. Its semi-crystalline structure makes it easy to undergo a cross-linking reaction with the toughening agent and the antioxidant when irradiated to form a network structure, so that the heat shrink tubing has good mechanical properties, is not easy to bend during use, and is easy to thread the tube. The use of the toughening agent can increase the compatibility between different components, reduce the overall crystallinity of the material, and make the heat shrink tubing have resilience and good tearability, and can also improve the elongation at break of the heat shrink tubing. In the embodiment of the present invention, the amount of the antioxidant used is small, which is conducive to reducing the introduction of colored substances, thereby better maintaining the transparency of the heat shrink tubing, making it easy to observe the welding points when the heat shrink tubing is used for pipe welding. In addition, when the primary tube is irradiated using a high-energy electron accelerator, multiple irradiations are performed, and the relative position of the high-energy electron accelerator and the primary tube is adjusted before each irradiation, so that all parts of the primary tube are irradiated more evenly, thereby preventing local positions of the primary tube from undergoing a rapid cross-linking reaction and releasing a large amount of heat due to excessive irradiation, thereby preventing local positions of the primary tube from softening, sticking, and then agglomerating due to heat, and making the performance of the heat shrink tube more uniform.

[0037] In an embodiment of the present invention, the polyethylene includes at least one of linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene. It should be understood that the polyethylene should have a suitable melt index. This is because when the melt index of the polyethylene is too high, its fluidity after melting is too strong, which is not conducive to dimensional control during the execution of the steps S2 and S4. When the melt index of the polyethylene is too low, its fluidity after melting is poor, resulting in the need to set more stringent processing parameters (mainly higher heating temperature) during the execution of the steps S1 and S2. In a preferred embodiment, the melt index of the polyethylene can be 1g / 10min to 5g / 10min. Here, the melt index of the polyethylene is determined using conventional methods.

[0038] The toughening agent includes at least one of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer. Similarly, the toughening agent should also have a suitable melt index, with an optional melt index of 0.5 g / 10 min to 5 g / 10 min.

[0039] Furthermore, the antioxidant includes at least one of 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane (a commercially available GA-80 antioxidant), dioctadecyl thiodipropionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] ester, N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, didodecyl thiodipropionate, tris[2,4-di-tert-butylphenyl]phosphite, and butylated hydroxytoluene, and preferably at least two. A composite antioxidant composed of at least two or more components is beneficial for reducing the amount of antioxidant used and further reducing the introduction of colored substances.

[0040] The step S1 can be performed using a twin-screw extruder. The twin-screw extruder can provide a large shear force, so that the premix is ​​fully blended to obtain a more uniform masterbatch. The temperature of each heating section of the twin-screw extruder is set to 270℉~400℉. In an illustrative implementation, the twin-screw extruder may include eleven heating sections, namely the first heating section, the second heating section, the third heating section, the fourth heating section, the fifth heating section, the sixth heating section, the seventh heating section, the eighth heating section, the ninth heating section, the tenth heating section, and the eleventh heating section (also referred to as the head section) arranged in sequence from the feed hopper to the extrusion port, wherein the temperature of the first heating section is 270℉~290℉, the temperature of the second heating section is 290℉~310℉, and the temperature of the third heating section is 270℉~290℉. The temperature is 310℉~330℉, the temperature of the fourth heating section is 330℉~350℉, the temperature of the fifth heating section is 350℉~370℉, the temperature of the sixth heating section is 350℉~370℉, the temperature of the seventh heating section is 370℉~390℉, the temperature of the eighth heating section is 370℉~390℉, the temperature of the ninth heating section is 370℉~390℉, the temperature of the tenth heating section is 380℉~400℉, and the temperature of the eleventh heating section is 380℉~400℉. The premix is ​​heated in each heating zone in the twin-screw extruder and experiences different temperatures. In other words, the premix is ​​heated to 270°F to 290°F in the first heating zone, to 290°F to 310°F in the second heating zone, to 310°F to 330°F in the third heating zone, to 330°F to 350°F in the fourth heating zone, to 350°F to 370°F in the fifth heating zone, to 350°F to 370°F in the sixth heating zone, to 370°F to 390°F in the seventh heating zone, to 370°F to 390°F in the eighth heating zone, to 370°F to 390°F in the ninth heating zone, to 380°F to 400°F in the tenth heating zone, and to 380°F to 400°F in the eleventh heating zone.

[0041] The step S2 can be performed using a single screw extruder with a suitable die and mandrel. The heating temperature of the single screw extruder is 330°F to 400°F. In an exemplary implementation, the single-screw extruder may include a twelfth heating section, a thirteenth heating section, a fourteenth heating section, a fifteenth heating section, a sixteenth heating section, a seventeenth heating section, an eighteenth heating section, and a nineteenth heating section (also referred to as a head section) sequentially arranged in a direction away from the feed port, wherein the temperature of the twelfth heating section is 310°F to 330°F, the temperature of the thirteenth heating section is 330°F to 350°F, the temperature of the fourteenth heating section is 340°F to 360°F, the temperature of the fifteenth heating section is 350°F to 370°F, the temperature of the sixteenth heating section is 370°F to 390°F, the temperature of the seventeenth heating section is 370°F to 390°F, the temperature of the eighteenth heating section is 370°F to 390°F, and the temperature of the nineteenth heating section is 380°F to 400°F. The masterbatch is heated in each heating section of the single-screw extruder and experiences different temperatures. That is, the masterbatch is heated to 310°F to 330°F in the 12th heating section, to 330°F to 350°F in the 13th heating section, to 340°F to 360°F in the 14th heating section, to 350°F to 370°F in the 15th heating section, to 370°F to 390°F in the 16th heating section, to 370°F to 390°F in the 17th heating section, to 370°F to 390°F in the 18th heating section, and to 380°F to 400°F in the 19th heating section. After extrusion, the masterbatch can be immersed in a coolant for cooling. The coolant temperature is 3°C to 5°C. This allows the extruded tube to cool rapidly at high temperature, significantly shortening the crystallization process of the tube and reducing the degree of crystallinity, thereby increasing the transparency of the primary tube and, consequently, increasing the transparency of the final heat shrink tubing.

[0042] In step S3, the energy of the high-energy electron accelerator is 5MeV to 10MeV, the dose during each irradiation is 15kGy to 40kGy, and the total dose for multiple irradiations is 400kGy to 800kGy. A higher total irradiation dose can ensure that the polyethylene, which serves as the main substrate, has a near-saturated degree of crosslinking, thereby imparting superior thermal stability to the heat-shrink tubing. In an optional implementation, "irradiating the nascent tubing multiple times with a high-energy electron beam under vacuum conditions" means that, prior to irradiation, the nascent tubing is wound into a coil and packaged, and the gas within the packaging material is evacuated so that the nascent tubing is vacuum-packaged, and then the vacuum-packaged nascent tubing is irradiated using the high-energy electron accelerator. Furthermore, a specific method for adjusting the relative orientation of the high-energy electron accelerator and the raw tubes before each irradiation is as follows: during the irradiation process, a whole tray of vacuum-packed raw tubes is placed on a conveying track, such as a circular conveying track (i.e., the conveying track is connected end to end), and is irradiated by the electron beam of the high-energy electron accelerator during the conveying process, and the raw tubes are flipped 180° after each round of irradiation. Here, flipping the raw tubes 180° specifically means that the whole tray of raw tubes has a first end face and a second end face that are opposite to each other in the axial direction. During the previous round of irradiation, if the second end face contacts the bearing surface of the conveying track and the first end face faces the high-energy electron accelerator, then during the next round of irradiation, the raw tubes are flipped so that the orientations of the first end face and the second end face are reversed, that is, the first end face contacts the bearing surface specified for conveying and the second end face faces the high-energy electron accelerator. In addition, after completing 5 to 10 rounds of irradiation, a pause is required before continuing irradiation. The pause time is controlled to be 60 minutes to 100 minutes.

[0043] Step S4 may specifically include heating the semi-finished tubular material to soften it. Then, gas is introduced into the inner cavity of the semi-finished tubular material to increase the radial dimension of the semi-finished tubular material under the action of the gas pressure. Finally, the semi-finished tubular material is cooled and shaped. In this step, the semi-finished tubular material may be heated in an oven at a temperature of 300°F to 572°F, with the introduced gas pressure of 0.4 MPa to 1.0 MPa. Depending on actual needs, the inner diameter of the semi-finished tubular material after radial expansion increases to 2 to 4 times its initial inner diameter (i.e., the inner diameter before the introduction of gas).

[0044] In addition, it should be noted that when the heat shrink tube is used in the field of medical devices, all raw materials (i.e., the polyethylene, the toughening agent, and the antioxidant) should be medical-grade raw materials, and all steps of the preparation method should be completed in a 100,000-class clean workshop, and irradiation should be performed in a closed packaging manner, so that the final heat shrink tube can pass the biocompatibility test and meet the use standards of medical devices.

[0045] Next, this article will describe the preparation method in detail with reference to specific examples.

[0046] <Example 1>

[0047] In this embodiment, the premix is ​​mixed by stirring with a high-speed stirrer the following components in the following mass percentages: 95% low-density polyethylene, 4.5% ethylene-methyl acrylate copolymer, 0.25% butylated hydroxytoluene, and 0.25% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0048] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch, wherein the temperature of the first heating zone was 275°F, the temperature of the second heating zone was 290°F, the temperature of the third heating zone was 310°F, the temperature of the fourth heating zone was 340°F, the temperature of the fifth heating zone was 360°F, the temperature of the sixth heating zone was 360°F, the temperature of the seventh heating zone was 370°F, the temperature of the eighth heating zone was 380°F, the temperature of the ninth heating zone was 380°F, the temperature of the tenth heating zone was 380°F, and the temperature of the head zone was 380°F.

[0049] In step S2, the masterbatch is extruded using a single-screw extruder having eight heating zones to obtain a green pipe, wherein the temperature of the twelfth heating zone is 310°F, the temperature of the thirteenth heating zone is 340°F, the temperature of the fourteenth heating zone is 340°F, the temperature of the fifteenth heating zone is 360°F, the temperature of the sixteenth heating zone is 370°F, the temperature of the seventeenth heating zone is 380°F, the temperature of the eighteenth heating zone is 380°F, and the temperature of the nineteenth heating zone is 380°F.

[0050] During irradiation, the energy of the high-energy electron accelerator was 10 MeV, the dose per irradiation was 20 kgy, and the total number of irradiations was 30, for a total dose of 600 kgy. Before each irradiation, the nascent tubing was packaged and the packaging evacuated to place the tubing in a vacuum environment. During irradiation, the entire tray of nascent tubing, including its packaging, was placed on a circulating conveyor track and exposed to the high-energy electron beam for irradiation. After each irradiation cycle, the nascent tubing was rotated 180°. After every 10 irradiation cycles, a 75-minute pause was performed before irradiation was repeated.

[0051] During the sizing expansion, the temperature of the oven is 350°F ± 10°F, the gas introduced is high-pressure nitrogen with a pressure of 0.45 MPa, and the inner diameter of the final heat shrinkable tube is 3.5 times the inner diameter of the semi-finished tube.

[0052] <Example 2>

[0053] In this embodiment, the premix is ​​mixed by stirring with a high-speed stirrer the following components in the following mass percentages: 60% linear low-density polyethylene, 20% low-density polyethylene, 19% ethylene-propyl acrylate copolymer, and 1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0054] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch. In the twin-screw extruder, the temperature of the first heating zone was 270°F, the temperature of the second heating zone was 290°F, the temperature of the third heating zone was 320°F, the temperature of the fourth heating zone was 350°F, the temperature of the fifth heating zone was 350°F, the temperature of the sixth heating zone was 360°F, the temperature of the seventh heating zone was 370°F, the temperature of the eighth heating zone was 390°F, the temperature of the ninth heating zone was 390°F, the temperature of the tenth heating zone was 390°F, and the temperature of the eleventh heating zone was 390°F.

[0055] In step S2, the masterbatch is extruded using a single-screw extruder having eight heating zones to obtain a green pipe, wherein the temperature of the twelfth heating zone is 320°F, the temperature of the thirteenth heating zone is 350°F, the temperature of the fourteenth heating zone is 350°F, the temperature of the fifteenth heating zone is 360°F, the temperature of the sixteenth heating zone is 380°F, the temperature of the seventeenth heating zone is 380°F, the temperature of the eighteenth heating zone is 380°F, and the temperature of the nineteenth heating zone is 380°F.

[0056] During irradiation, the energy of the high-energy electron accelerator was 5 MeV, the dose per irradiation was 25 kGy, and the total number of irradiation cycles was 17, for a total dose of 425 kGy. Before each irradiation cycle, the raw tubing was packaged and evacuated to a vacuum environment. During irradiation, the entire tray of raw tubing was placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the raw tubing was rotated 180°. After completing six irradiation cycles, a 65-minute pause was required before continuing irradiation.

[0057] During the sizing expansion, the temperature of the oven is 350°F ± 10°F, the gas introduced is high-pressure nitrogen, and the pressure is 0.8 MPa. The inner diameter of the final heat shrinkable tube is 4 times the inner diameter of the semi-finished tube.

[0058] <Example 3>

[0059] In this embodiment, the premix is ​​mixed by stirring with a high-speed stirrer the following components in percentage by mass: 25% medium-density polyethylene, 70% low-density polyethylene, 4% ethylene-vinyl acetate copolymer, 0.5% butylated hydroxytoluene, 0.3% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 0.2% tris[2,4-di-tert-butylphenyl]phosphite.

[0060] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch, wherein the temperature of the first heating zone was 275°F, the temperature of the second heating zone was 295°F, the temperature of the third heating zone was 315°F, the temperature of the fourth heating zone was 345°F, the temperature of the fifth heating zone was 365°F, the temperature of the sixth heating zone was 370°F, the temperature of the seventh heating zone was 380°F, the temperature of the eighth heating zone was 390°F, the temperature of the ninth heating zone was 390°F, the temperature of the tenth heating zone was 395°F, and the temperature of the eleventh heating zone was 395°F.

[0061] In step S2, the masterbatch is extruded using a single-screw extruder having eight heating zones to obtain a green pipe, wherein the temperature of the twelfth heating zone is 325°F, the temperature of the thirteenth heating zone is 345°F, the temperature of the fourteenth heating zone is 355°F, the temperature of the fifteenth heating zone is 370°F, the temperature of the sixteenth heating zone is 370°F, the temperature of the seventeenth heating zone is 385°F, the temperature of the eighteenth heating zone is 385°F, and the temperature of the nineteenth heating zone is 385°F.

[0062] During irradiation, the energy of the high-energy electron accelerator was 10 MeV, the dose per irradiation was 25 kGy, and the total number of irradiation sessions was 22, for a total dose of 550 kGy. Before each irradiation session, the raw tubing was packaged and evacuated to a vacuum environment. During irradiation, the entire tray of raw tubing was placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the raw tubing was rotated 180°. After every seven irradiation cycles, an 85-minute pause was required before irradiation was repeated.

[0063] During the sizing expansion, the oven temperature was set at 350°F ± 10°F, and the gas introduced was high-pressure nitrogen at a pressure of 0.56 MPa. The inner diameter of the resulting heat shrink tubing was four times that of the semi-finished tubing.

[0064] <Example 4>

[0065] In this embodiment, the premix is ​​stirred and mixed by a high-speed stirrer with the following components in percentage by mass: 68.5% high-density polyethylene, 4.5% ethylene-vinyl acetate copolymer, 25% ethylene-propyl acrylate copolymer, 1.2% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 0.8% tris[2,4-di-tert-butylphenyl]phosphite.

[0066] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch, wherein the temperature of the first heating zone was 290°F, the temperature of the second heating zone was 310°F, the temperature of the third heating zone was 330°F, the temperature of the fourth heating zone was 350°F, the temperature of the fifth heating zone was 370°F, the temperature of the sixth heating zone was 370°F, the temperature of the seventh heating zone was 390°F, the temperature of the eighth heating zone was 390°F, the temperature of the ninth heating zone was 390°F, the temperature of the tenth heating zone was 400°F, and the temperature of the first heating zone was 400°F.

[0067] In step S2, the masterbatch is extruded using a single-screw extruder having eight heating zones to obtain a green pipe, wherein the temperature of the twelfth heating zone is 330°F, the temperature of the thirteenth heating zone is 350°F, the temperature of the fourteenth heating zone is 360°F, the temperature of the fifteenth heating zone is 370°F, the temperature of the sixteenth heating zone is 370°F, the temperature of the seventeenth heating zone is 390°F, the temperature of the eighteenth heating zone is 390°F, and the temperature of the nineteenth heating zone is 400°F.

[0068] During irradiation, the energy of the high-energy electron accelerator was 10 MeV, the dose per irradiation was 16 kGy, and the total number of irradiation cycles was 50, for a total dose of 800 kGy. Before each irradiation cycle, the raw tubing was packaged and evacuated to a vacuum environment. During irradiation, the entire tray of raw tubing was placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the raw tubing was rotated 180°. After every 10 irradiation cycles, a 95-minute pause was required before irradiation was repeated.

[0069] During the sizing expansion, the oven temperature was maintained at 350°F ± 10°F, and the gas introduced was high-pressure nitrogen at a pressure of 0.40 MPa. The inner diameter of the resulting heat shrink tubing was 2.5 times the inner diameter of the semi-finished tubing.

[0070] <Comparative Example 1>

[0071] In this comparative example, the premix is ​​stirred and mixed by a high-speed stirrer with the following components in percentage by mass: 80% of low-density polyethylene, 13% of ethylene-vinyl acetate copolymer, 0.5% of dibutylhydroxytoluene, and 0.5% of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, 3% of triallyl isocyanurate, and 3% of silicone lubricant.

[0072] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch, wherein the temperature of the first heating zone was 280°F, the temperature of the second heating zone was 295°F, the temperature of the third heating zone was 320°F, the temperature of the fourth heating zone was 350°F, the temperature of the fifth heating zone was 365°F, the temperature of the sixth heating zone was 365°F, the temperature of the seventh heating zone was 375°F, the temperature of the eighth heating zone was 380°F, the temperature of the ninth heating zone was 380°F, the temperature of the tenth heating zone was 390°F, and the temperature of the head zone was 390°F.

[0073] The masterbatch was then extruded using a single-screw extruder with eight heating zones to produce a green pipe. The temperature of the twelfth heating zone was 310°F, the temperature of the thirteenth heating zone was 340°F, the temperature of the fourteenth heating zone was 340°F, the temperature of the fifteenth heating zone was 360°F, the temperature of the sixteenth heating zone was 370°F, the temperature of the seventeenth heating zone was 380°F, the temperature of the eighteenth heating zone was 380°F, and the temperature of the nineteenth heating zone was 380°F.

[0074] The nascent tubes are then irradiated using a high-energy electron accelerator. The energy of the high-energy electron accelerator is 10 MeV, and the dose per irradiation is 20 kGy. The total number of irradiations is 30, for a total dose of 600 kGy. Before each irradiation, the nascent tubes are packaged and evacuated to a vacuum environment. During irradiation, the entire tray of nascent tubes is placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the tubes are rotated 180°. After every 10 irradiation cycles, a 75-minute pause is performed before irradiation is repeated.

[0075] During the sizing expansion, the temperature of the oven is 350°F ± 10°F, the gas introduced is high-pressure nitrogen with a pressure of 0.45 MPa, and the inner diameter of the heat shrinkable tube finally obtained is 4 times the inner diameter of the semi-finished tube.

[0076] In this comparative example, triallyl isocyanurate was added as a sensitizer. Although it can reduce the irradiation dose during subsequent irradiation, the addition of the sensitizer makes it difficult to mix the various raw materials evenly. This leads to inconsistent composition in various regions of the prepared primary tubing. Furthermore, when the primary tubing is irradiated using a high-energy electron accelerator, significant differences in the degree of cross-linking in different regions of the primary tubing occur, resulting in product wall deviation during subsequent sizing and expansion of the tubing. Therefore, this comparative example also adds a silicone lubricant to promote sufficient mixing of the various raw materials. However, this results in poor surface smoothness of the extruded tubing, resulting in poor appearance of the finished medical heat shrink tubing during actual use, which in turn causes surface defects in the auxiliary welded tubing, affecting the tensile properties and pressure resistance of the welded tubing.

[0077] <Comparative Example 2>

[0078] In this comparative example, the premix was stirred and mixed by a high-speed stirrer with the following components in percentage by mass: 95% polypropylene, 4% ethylene-vinyl acetate copolymer, 0.5% butylated hydroxytoluene, 0.3% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, and 0.2% tris[2,4-di-tert-butylphenyl]phosphite.

[0079] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch, wherein the temperature of the first heating zone was 275°F, the temperature of the second heating zone was 295°F, the temperature of the third heating zone was 325°F, the temperature of the fourth heating zone was 335°F, the temperature of the fifth heating zone was 345°F, the temperature of the sixth heating zone was 360°F, the temperature of the seventh heating zone was 360°F, the temperature of the eighth heating zone was 370°F, the temperature of the ninth heating zone was 370°F, the temperature of the tenth heating zone was 375°F, and the temperature of the eleventh heating zone was 375°F.

[0080] The masterbatch was then extruded using a single-screw extruder with eight heating zones to produce a green pipe. The temperature of the twelfth heating zone was 325°F, the temperature of the thirteenth heating zone was 340°F, the temperature of the fourteenth heating zone was 350°F, the temperature of the fifteenth heating zone was 360°F, the temperature of the sixteenth heating zone was 360°F, the temperature of the seventeenth heating zone was 370°F, the temperature of the eighteenth heating zone was 370°F, and the temperature of the nineteenth heating zone was 370°F.

[0081] The nascent tubes are then irradiated using a high-energy electron accelerator. The energy of the high-energy electron accelerator is 10 MeV, and the dose per irradiation is 25 kGy. A total of 22 irradiation cycles are performed, for a total dose of 550 kGy. Before each irradiation cycle, the nascent tubes are packaged and evacuated to a vacuum environment. During irradiation, the entire tray of nascent tubes is placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the tubes are rotated 180°. After every seven irradiation cycles, an 85-minute pause is required before irradiation is repeated.

[0082] During the sizing expansion, the temperature of the oven is 350°F ± 10°F, the gas introduced is high-pressure nitrogen with a pressure of 0.62 MPa, and the inner diameter of the final heat shrinkable tube is 2.5 times the inner diameter of the semi-finished tube.

[0083] The polymer used in this comparative example is polypropylene, which has poor ductility. Therefore, when the fixed diameter is expanded, a heat shrink tube with a larger inner diameter cannot be obtained.

[0084] <Comparative Example 3>

[0085] In this comparative example, the premix is ​​mixed by stirring with a high-speed stirrer the following components in percentage by mass: 75% of low-density polyethylene, 20% of polyethylene terephthalate, 4.5% of ethylene-methyl acrylate copolymer, 0.25% of butylated hydroxytoluene, and 0.25% of pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0086] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch, wherein the temperature of the first heating zone was 340°F, the temperature of the second heating zone was 350°F, the temperature of the third heating zone was 370°F, the temperature of the fourth heating zone was 370°F, the temperature of the fifth heating zone was 390°F, the temperature of the sixth heating zone was 390°F, the temperature of the seventh heating zone was 390°F, the temperature of the eighth heating zone was 400°F, the temperature of the ninth heating zone was 400°F, the temperature of the tenth heating zone was 400°F, and the temperature of the head zone was 420°F.

[0087] The masterbatch was then extruded using a single-screw extruder with eight heating zones to produce a green pipe. The temperature of the twelfth heating zone was 370°F, the temperature of the thirteenth heating zone was 380°F, the temperature of the fourteenth heating zone was 380°F, the temperature of the fifteenth heating zone was 390°F, the temperature of the sixteenth heating zone was 400°F, the temperature of the seventeenth heating zone was 410°F, the temperature of the eighteenth heating zone was 410°F, and the temperature of the nineteenth heating zone was 410°F.

[0088] The nascent tubes are then irradiated using a high-energy electron accelerator. The energy of the high-energy electron accelerator is 10 MeV, and the dose per irradiation is 20 kGy. A total of 30 irradiation sessions are performed, for a total dose of 600 kGy. Before each irradiation session, the nascent tubes are packaged and evacuated to a vacuum environment. During irradiation, the entire tray of nascent tubes is placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the tubes are rotated 180°. After every 10 irradiation cycles, a 75-minute pause is performed before irradiation is repeated.

[0089] During the sizing expansion, the temperature of the oven is 350°F ± 10°F, the gas introduced is high-pressure nitrogen with a pressure of 0.65 MPa, and the inner diameter of the heat shrinkable tube finally obtained is 3 times the inner diameter of the semi-finished tube.

[0090] The polymers used in this comparative example are polyethylene and polyethylene terephthalate. Among them, polyethylene terephthalate has greater rigidity, resulting in poor flexibility and low-temperature resistance of the finished medical heat shrink tubing. In addition, greater gas pressure is required during caliber expansion, and higher requirements are placed on the safety performance of the caliber expansion equipment, resulting in increased production costs.

[0091] <Comparative Example 4>

[0092] In this embodiment, the premix is ​​mixed by stirring with a high-speed stirrer the following components in the following mass percentages: 60% linear low-density polyethylene, 20% low-density polyethylene, 19% ethylene-propyl acrylate copolymer, and 1% pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate.

[0093] The premix was extruded and pelletized using a twin-screw extruder with eleven heating zones to obtain a masterbatch. In the twin-screw extruder, the temperature of the first heating zone was 270°F, the temperature of the second heating zone was 290°F, the temperature of the third heating zone was 320°F, the temperature of the fourth heating zone was 350°F, the temperature of the fifth heating zone was 350°F, the temperature of the sixth heating zone was 360°F, the temperature of the seventh heating zone was 370°F, the temperature of the eighth heating zone was 390°F, the temperature of the ninth heating zone was 390°F, the temperature of the tenth heating zone was 390°F, and the temperature of the eleventh heating zone was 390°F.

[0094] The masterbatch was then extruded using a single-screw extruder with eight heating zones to produce a green pipe. The temperature of the twelfth heating zone was 320°F, the temperature of the thirteenth heating zone was 350°F, the temperature of the fourteenth heating zone was 350°F, the temperature of the fifteenth heating zone was 360°F, the temperature of the sixteenth heating zone was 380°F, the temperature of the seventeenth heating zone was 380°F, the temperature of the eighteenth heating zone was 380°F, and the temperature of the nineteenth heating zone was 380°F.

[0095] The nascent tubes were then irradiated using a medium-energy electron accelerator at an energy of 1.5 MeV. Each irradiation dose was 25 kGy, and the total number of irradiation cycles was 17, for a total dose of 425 kGy. Before each irradiation cycle, the nascent tubes were packaged and evacuated to a vacuum environment. During irradiation, the entire tray of nascent tubes was placed on a circulating conveyor track and exposed to the high-energy electron beam. After each irradiation cycle, the tubes were rotated 180°. After every six irradiation cycles, a 65-minute pause was required before irradiation was repeated.

[0096] During sizing expansion, the oven temperature is 350°F ± 10°F, and the gas introduced is high-pressure nitrogen at a pressure of 0.68 MPa. Ultimately, only 10% of the raw tubing on the outer periphery of the reel can be expanded into the finished thermoplastic tubing. The inner diameter of the finished heat shrink tubing is four times that of the semi-finished product.

[0097] Since the heat shrink tubing obtained in this comparative example was irradiated as a whole roll, the energy of the medium-energy electron accelerator was insufficient to penetrate all the primary tubing, resulting in a decrease in the degree of irradiation cross-linking from the outside to the inside. As a result, most of the tubing could not be processed during the sizing expansion process due to the low degree of cross-linking, and was prone to explosion.

[0098] <Comparative Example 5>

[0099] The raw materials used in this comparative example, as well as the steps and processing parameters for obtaining the raw pipe, are the same as those in comparative example 4.

[0100] The nascent tubes were then irradiated using a high-energy electron accelerator. The energy was 10 MeV, and the dose per irradiation was 25 kGy. The total number of irradiation cycles was 17, for a total dose of 425 kGy. Before each irradiation cycle, the nascent tubes were packaged and evacuated to a vacuum environment. During irradiation, the entire tray of nascent tubes was placed on a circulating conveyor track and placed under the high-energy electron beam for irradiation, maintaining a constant relative position throughout the process. After completing six irradiation cycles, a 65-minute pause was required before continuing.

[0101] During sizing expansion, the oven temperature is 350°F ± 10°F, and the gas introduced is high-pressure nitrogen at a pressure of 0.8 MPa. Ultimately, only 40% of the raw tube can be expanded into finished heat shrink tubing. The inner diameter of the finished heat shrink tubing is four times that of the semi-finished product.

[0102] In this comparative example, irradiation was performed on only one side of the heat-shrink tubing, resulting in poor irradiation uniformity. Furthermore, uneven heating on the side of the nascent tubing directly facing the high-energy electron beam caused it to clump together, resulting in a semi-finished product length reduction of only 70%. Furthermore, the nitrogen pressure required for sizing and expansion fluctuated significantly, resulting in poor expansion stability.

[0103] <Comparative Example 6>

[0104] The raw materials used in this comparative example, as well as the steps and processing parameters for obtaining the raw pipe, are the same as those in comparative example 4.

[0105] The nascent tubes are then irradiated using a high-energy electron accelerator. The energy used is 10 MeV, and the total dose is 425 kGy. Before each irradiation, the nascent tubes are packaged and evacuated to a vacuum environment. During irradiation, the entire tray of nascent tubes is placed on a circulating conveyor and exposed to the high-energy electron beam for 5 minutes.

[0106] Lengthening is performed before sizing and expansion, with a lengthening rate of 0%. Since the nascent pipe receives too much radiation at one time, a large amount of heat is generated in a short period of time, and the heat cannot be dissipated in time, resulting in large areas of semi-finished products sticking to each other and agglomerating, causing serious deformation and making it impossible to lengthen.

[0107] While the present invention is disclosed above, it is not limited thereto. Those skilled in the art may make various modifications and variations to the present invention without departing from the spirit and scope of the present invention. Thus, the present invention is intended to encompass such modifications and variations as long as they fall within the scope of the claims and their equivalents.

Claims

1. A medical heat shrink tubing, characterized in that: The invention is composed of the following components by mass percentage: 65% to 95% of polyethylene, 3% to 30% of a toughening agent, and 0.5% to 5% of an antioxidant; The toughening agent includes at least one of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer; The medical heat shrink tubing is prepared by the following steps: Mixing polyethylene, the toughening agent and the antioxidant and extruding and granulating the mixture to form a masterbatch; extruding the masterbatch and cooling it to obtain a green tube; Under vacuum conditions, the raw tube is irradiated multiple times using a high-energy electron accelerator to obtain a semi-finished tube; before each irradiation, the relative position of the high-energy electron accelerator and the raw tube is adjusted; the energy of the high-energy electron accelerator is 5MeV to 10MeV, and the dose of each irradiation is 15kGy to 60kGy, and the total dose of the multiple irradiations is 400kGy to 800kGy; and The semi-finished pipe is expanded to obtain a heat shrinkable tube.

2. The medical heat shrink tube according to claim 1, characterized in that: The polyethylene includes at least one of linear low-density polyethylene, low-density polyethylene, medium-density polyethylene, and high-density polyethylene.

3. The medical heat shrink tube according to claim 1 or 2, characterized in that: The polyethylene has a melt index of 1 g / 10 min to 5 g / 10 min.

4. The medical heat shrink tube according to claim 1, characterized in that: The melt index of the toughening agent is 0.5 g / 10 min to 5 g / 10 min.

5. The medical heat shrink tube according to claim 1, characterized in that: The antioxidant includes at least one of 3,9-bis[2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)-propionyloxy]-1,1-dimethylethyl]-2,4,8,10-tetraoxaspiro[5.5]undecane, dioctadecyl thiodipropionate, pentaerythritol tetrakis[β-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], N,N'-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl]hydrazine, didodecyl thiodipropionate, tris[2,4-di-tert-butylphenyl]phosphite, and dibutylhydroxytoluene.

6. A method for preparing a medical heat shrink tubing, characterized in that: The preparation method comprises the following steps: The premix is ​​extruded and granulated to form a masterbatch; the premix is ​​composed of the following components in percentage by mass: 65% to 95% of polyethylene, 3% to 30% of a toughening agent, and 0.5% to 5% of an antioxidant; wherein the toughening agent comprises at least one of ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-methyl acrylate copolymer, ethylene-propyl acrylate copolymer, and ethylene-butyl acrylate copolymer; extruding the masterbatch and cooling it to obtain a green tube; Under vacuum conditions, the raw tube is irradiated multiple times using a high-energy electron accelerator to obtain a semi-finished tube; before each irradiation, the relative position of the high-energy electron accelerator and the raw tube is adjusted; the energy of the high-energy electron accelerator is 5MeV to 10MeV, and the dose of each irradiation is 15kGy to 60kGy, and the total dose of the multiple irradiations is 400kGy to 800kGy; and The semi-finished pipe is expanded to obtain a heat shrinkable tube.

7. The method for preparing a medical heat shrinkable tube according to claim 6, wherein: Extruding the premix into pellets using a twin-screw extruder, wherein the heating temperature of the twin-screw extruder is 270°F to 400°F; and / or, The masterbatch is extruded through a single-screw extruder to obtain the green pipe, and the heating temperature of the single-screw extruder is 330°F to 400°F.

8. The method for preparing a medical heat shrink tube according to claim 6, wherein: After being extruded, the masterbatch is immersed in a cooling liquid for cooling, and the temperature of the cooling liquid is 3° C. to 5° C.

9. The method for preparing a medical heat shrink tube according to claim 6, wherein: The raw tube is wound into a disk and has a first end face and a second end face opposite to each other in the axial direction; Adjusting the relative orientation of the high-energy electron accelerator and the primary tube before each irradiation means that, during the previous irradiation, one of the first end face and the second end face is facing the high-energy electron accelerator, and before the next irradiation, the primary tube is flipped 180° so that the other of the first end face and the second end face is facing the high-energy electron accelerator.

10. The method for preparing a medical heat shrink tube according to claim 6, wherein: The step of sizing the semi-finished tube includes: heating the semi-finished tube to soften the semi-finished tube, then introducing gas into the inner cavity of the semi-finished tube so that the radial dimension of the semi-finished tube increases under the action of the gas pressure, and finally cooling the semi-finished tube to obtain the heat shrink tube.

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