Easily stripped heat shrinkable tube and preparation method thereof

Abstract

The invention discloses an easy-to-peel heat-shrinkable tube, which adopts an ethylene-acrylate copolymer and a reinforcing agent as matrix resin, and because ethylene-acrylate is a copolymer and contains an acrylate side group, the crystallization of ethylene-acrylate is disturbed, the distance between main chain vinyl molecules is increased, and the entanglement structure of molecules is reduced, so that the heat-shrinkable tube is easy to peel off. By adding the ethylene-acrylate copolymer, the cohesion strength of an ethylene-acrylate molecular chain is reduced, the tensile strength of the molecular structure can be improved by adding the reinforcing agent, and the orientation degree of the molecular chain in a blend of the ethylene-acrylate copolymer and the reinforcing agent is further controlled through an extrusion process to ensure that the orientation degree is within a certain range. The ethylene-acrylate copolymer and reinforcing agent blend molecular chains and chain segments extend from a freely curled disordered state to the orientation direction, the molecular entanglement structure is reduced, meanwhile, the tensile strength of the molecular structure is enhanced, and the oriented ordered state change enables the tensile strength of the blend in the length direction of the pipe to be remarkably improved; the strength in the direction perpendicular to the length direction of the pipe is reduced, so that the tearability of the pipe is realized, and the tensile strength of the pipe is further improved; the tearable pipe is manufactured into the heat shrink tube through irradiation and expansion processes, the manufactured heat shrink tube has the same tearability as that before tube expansion, and the normal-temperature tearable performance of the easy-to-peel heat shrink tube is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of heat shrinkable tubes, and particularly to an easily peelable heat shrinkable tube and a preparation method thereof. Background Art

[0002] The easily peelable heat shrinkable tube is mainly used for the protection or auxiliary shrinkage of precision devices, electronic components, medical devices, etc. For example, it is used to assist the shrinkage of non-shrinkable polymer tubes onto corresponding mandrels in medical devices or act on medical laser welding products. The easily peelable heat shrinkable tube can be easily removed without residue at any angle from one end along the axial direction (with a defect pre-made at one end of the tube to facilitate peeling) without using mechanical removal (such as shaving, scratching, cutting, grinding, etc., which may cause defects or damage to the internal material) after completing the auxiliary shrinkage. After removing the easily peelable heat shrinkable tube, the surface of the non-shrinkable polymer tube is smooth, without defects and residue.

[0003] Currently, the room temperature tearable heat shrinkable tubes available on the market are generally fluororesin (FEP) easily peelable heat shrinkable tubes, and there are relatively few easily peelable heat shrinkable tubes made of polyolefins and their copolymers. Summary of the Invention

[0004] The main purpose of the present invention is to provide an easily peelable heat shrinkable tube made of polyolefins and their copolymer resins and a reinforcing agent, which has a lower tear strength than the FEP easily peelable heat shrinkable tube, a higher tensile strength, and no adhesion to the internal material, and can completely replace the FEP easily peelable heat shrinkable tube, providing a new choice for easily peelable heat shrinkable tubes.

[0005] To achieve the above object, the present invention provides an easily peelable heat shrinkable tube that has linear tearability in the length direction of the tube. Calculated by weight parts, the preparation materials of the easily peelable heat shrinkable tube include the following components:

[0006] Ethylene-acrylate copolymer: 20 - 90 parts;

[0007] Reinforcing agent: 10 - 80 parts.

[0008] In some embodiments of the present application, the ethylene-acrylate copolymer includes at least one of ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), and ethylene-methyl methacrylate copolymer (EMMA).

[0009] In some embodiments of the present application, the reinforcing agent includes at least one of polyethylene (PE), polyolefin elastomer (POE), and ethylene-vinyl acetate copolymer (EVA).

[0010] In some embodiments of the present application, the ethylene-acrylate copolymer has a melt index of (0.5 - 10) g / 10 min and an acrylic acid content of 9 wt% - 30 wt%;

[0011] Or, the tear strength of the ethylene-acrylate copolymer is less than 75 kN / m;

[0012] Or, the tensile strength of the ethylene-acrylate copolymer is 15 - 24 Mpa.

[0013] In some embodiments of the present application, the polyethylene (PE) is low-density polyethylene (LDPE), and the low-density polyethylene (LDPE) has a melt index of (0.3 - 7) g / 10 min and a tensile strength of 17 - 30 Mpa;

[0014] Or, the polyethylene (PE) is linear low-density polyethylene (LLDPE), and the linear low-density polyethylene (LLDPE) has a melt index of (0.3 - 10) g / 10 min and a tensile strength of 20 - 35 Mpa;

[0015] Or, the polyethylene (PE) is medium-density polyethylene (MDPE), and the medium-density polyethylene (MDPE) has a melt index of (0.3 - 10) g / 10 min and a tensile strength of 25 - 35 Mpa;

[0016] Or, the polyethylene (PE) is high-density polyethylene (HDPE), and the high-density polyethylene (HDPE) has a melt index of (0.3 - 10) g / 10 min and a tensile strength of 28 - 40 Mpa.

[0017] In some embodiments of the present application, the polyolefin elastomer (POE) has a melt index of (0.5 - 5) g / 10 min, a tensile strength of 18 - 40 Mpa, and a melting temperature of 70 - 110 °C.

[0018] In some embodiments of the present application, the ethylene-vinyl acetate copolymer (EVA) has a melt index of (0.5 - 7) g / 10 min, a tensile strength of 16 - 25 Mpa, and the vinyl acetate (VA) content does not exceed 20%.

[0019] In some embodiments of the present application, calculated by weight, the preparation materials of the easily peelable heat shrinkable tube further include the following additives:

[0020] 0.05 - 0.3 parts of antioxidant;

[0021] 0.05 - 0.1 part of lubricant;

[0022] Among them, the antioxidant includes at least one of an asymmetric hindered phenol antioxidant, an aromatic amine antioxidant, a thioether antioxidant, and a phosphite antioxidant;

[0023] The lubricant includes at least one of PTFE powder, zinc stearate, magnesium stearate, silicone, calcium stearate, or ethylene bisstearamide.

[0024] To achieve the above object, the present invention also provides a preparation method for an easily peelable heat shrinkable tube, including the following steps:

[0025] Masterbatch processing: Mix the ethylene-acrylate copolymer and the reinforcing agent evenly according to the ratio, extrude, draw into strips, and pelletize through an extrusion device to obtain masterbatch particles;

[0026] Extrusion into a tube: Extrude the obtained masterbatch particles through an extruder to obtain a semi-finished tube. Among them, control the orientation degree of the molecular chain of the extruded tube to be 40%-95%;

[0027] Irradiation process: Irradiate the above semi-finished tube through an irradiation device, control the irradiation dose to be 100-300 KGy, and obtain an irradiated tube;

[0028] Expansion molding: Expand the above irradiated tube at 130-260 °C, and then cool and shape it to obtain an easily peelable heat shrinkable tube; among them, after the easily peelable heat shrinkable tube shrinks by more than 35% at 200 °C, the molecular chain orientation degree is 30%-85%.

[0029] In some embodiments of the present application, in the masterbatch processing step, when the ethylene-acrylate copolymer and the reinforcing agent are mixed, an antioxidant and a lubricant can also be added for mixing;

[0030] Or, in the masterbatch processing step, the mixing time is 3-5 min;

[0031] Or, in the masterbatch processing step, the extrusion temperature of the extrusion device is 130-200 °C;

[0032] Or, in the extrusion into a tube step, the orientation degree of the molecular chain of the extruded tube is 50%-90%;

[0033] Or, in the expansion molding step, cool and shape it to obtain an easily peelable heat shrinkable tube. Among them, after the easily peelable heat shrinkable tube shrinks by more than 35% at 200 °C, the molecular chain orientation degree is 40%-85%.

[0034] The beneficial effects that the present invention can achieve:

[0035] The easy-to-peel heat shrink tube adopts ethylene-acrylate copolymer and reinforcing agent as base resin. Since ethylene-acrylate is a copolymer and contains acrylate side groups, its crystallization is disrupted, the distance between main chain vinyl molecules is increased, and the entangled structure of molecules is reduced, so that the cohesive strength of ethylene-acrylate molecular chains decreases. The reinforcing agent is added to improve the tensile strength of the molecular structure. The orientation degree of the internal molecular chains of the ethylene-acrylate copolymer and the reinforcing agent blend is further controlled through the extrusion process to ensure that the orientation degree is within a certain range, so that the ethylene-acrylate copolymer The molecular chains and segments of the material and reinforcer blend stretch from a freely curled disordered state to an oriented direction, which reduces the entangled structure of the molecules and enhances the tensile strength of the molecular structure. The ordered change in orientation significantly improves the tensile strength of the blend along the length of the tube, while the strength in the direction perpendicular to the length of the tube decreases, which not only achieves the tearability of the tube but also further improves the tensile strength of the tube. The tearable tube is made into a heat shrinkable tube through irradiation and expansion process. The heat shrinkable tube has the same tearability as before expansion, achieving the room-temperature tearability of the easy-to-peel heat shrinkable tube. DETAILED DESCRIPTION

[0036] It should be understood that the specific embodiments described herein are only used to explain the present invention, and are not used to limit the present invention.

[0037] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0038] In the present invention, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in the field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0039] The present invention provides an easily peelable heat shrinkable tube, which has linear tearing properties in the length direction of the tube. The easily peelable heat shrinkable tube preparation material includes the following components calculated by weight:

[0040] Ethylene-acrylate copolymer: 20-90 parts;

[0041] Reinforcing agent: 10 - 80 parts.

[0042] Ethylene - acrylate copolymer is formed by copolymerizing ethylene with acrylate, mainly including ethylene - methyl acrylate copolymer (EMA), ethylene - ethyl acrylate copolymer (EEA), ethylene - butyl acrylate copolymer (EBA), and ethylene - methyl methacrylate copolymer (EMMA). The properties of ethylene - acrylate copolymer are related to the content of acrylate monomers, average molecular weight, molecular weight distribution, long - chain branches and short - chain branches.

[0043] The reinforcing agent includes at least one of polyethylene (PE), polyolefin elastomer (POE), and ethylene - vinyl acetate copolymer (EVA). Polyethylene is a thermoplastic plastic polymerized from ethylene. Due to the different densities of the resins obtained by different polymerization methods, it is divided into high - density polyethylene (HDPE), medium - density polyethylene (MDPE), linear low - density polyethylene (LLDPE), and low - density polyethylene (LDPE). The polyolefin elastomer (POE) can be one of the random copolymer elastomers of ethylene and 1 - butene, ethylene and 1 - hexene, ethylene and 1 - octene, etc.; when using ethylene - vinyl acetate copolymer (EVA), the reinforcing effect is better when the content of vinyl acetate (VA) is less than 20%.

[0044] The polymer orientation structure refers to the structure in which molecular chains or other structural units are preferentially arranged and frozen along the direction of external force under the action of a certain external force. The melt - extruded ethylene - acrylate copolymer and reinforcing agent blend undergoes a stretching process, and the molecular chains of the ethylene - acrylate copolymer and reinforcing agent blend are arranged along the stretching direction, that is, preferentially oriented along the stretching direction.

[0045] The polymer material exists in a state where the molecular chains that make it up are entangled in a wool ball shape. In the molded article formed using the polymer material, the entangled state of the molecules is also maintained, and the physical properties of the molded article are greatly affected by the structure of the molecular entanglement. During the research on peelable pipes, we unexpectedly found that when ethylene-acrylate copolymer is used as the matrix resin and the degree of orientation is ensured to be in the range of 40%-95%, a peelable pipe with linear tearability in the length direction of the pipe can be prepared. This may be due to the special structure of substances such as ethylene-acrylate copolymer. Since it contains short branched chains such as methyl acrylate, ethyl acrylate, butyl acrylate, and methyl methacrylate, its crystallization is disrupted, the distance between the main chain vinyl molecules is increased, the cohesive strength of the ethylene-acrylate copolymer molecular chains is decreased, the structure of molecular entanglement is reduced, and the addition of a reinforcing agent can increase the tensile strength of the molecular structure. Further, by controlling the degree of orientation of the molecular chains inside the ethylene-acrylate copolymer and reinforcing agent blend through the extrusion process, ensuring that the degree of orientation is in the range of 40%-95%, the molecular chains and segments of the ethylene-acrylate copolymer and reinforcing agent blend extend from the disordered state of free curling to the orientation direction, reducing the linear entanglement structure of the blend molecules. The reinforcing agent has the characteristics of high crystallinity or long branched chains. Reinforcing agents with high crystallinity such as PE or EVA will cause the crystallization of the reinforcing agent to change from spherulites to monoclinic crystals during the extrusion and stretching orientation of the pipe. The formation of monoclinic crystals can not only increase the tensile strength in the orientation direction but also increase the number of physical cross-linking points formed by the blend molecular chains and segments in the orientation direction (i.e., along the length direction of the pipe), thereby significantly increasing the tensile strength of the pipe in the orientation direction; while reinforcing agents containing long branched chains, such as POE or LDPE, can form certain physical cross-linking points with the crystallization region of the ethylene-acrylate copolymer. During the extrusion and stretching orientation, the ethylene-acrylate copolymer is stretched and oriented from spherulites to monoclinic crystals, forming physical cross-linking points with the oriented long branched chain molecules, increasing the strength in the orientation direction, while the physical cross-linking points perpendicular to the orientation direction will be significantly reduced, resulting in a lower strength in the direction perpendicular to the orientation. By adding an appropriate proportion of the reinforcing agent and controlling the degree of orientation during the extrusion and stretching process, when the ethylene-acrylate copolymer is oriented, a reinforcing unit similar to a fiber appears along the orientation direction, further improving the tearability of the pipe. Therefore, the addition of the reinforcing agent can not only increase the tensile strength of the pipe in the orientation direction but also further improve its tearability along the length direction of the pipe. Further, through the irradiation process, the pipe is irradiated and crosslinked to change its ordinary two-dimensional linear molecular structure into a three-dimensional network molecular structure. The three-dimensional network molecular structure not only plays a role in curing the orientation of the molecular chains of the extruded pipe during the extrusion process but also enables the subsequent expansion process.However, at an expansion temperature of 130 - 260°C, the three-dimensional network molecules in the backward direction will shrink, which will change their degree of orientation. By controlling the appropriate irradiation dose and the crosslinking degree of the blend molecules during the irradiation process, it is finally achieved that after the easy-peel heat shrinkable tube shrinks by more than 35% at 200°C, the degree of orientation of the molecular chains of the easy-peel heat shrinkable tube is 30% - 85%, making it have the performance of being tearable at room temperature.

[0046] When the content of acrylate monomers in the ethylene-acrylate copolymer increases, the orderliness of its molecular chains is further reduced, and at the same time, the content of acrylic acid side groups is increased, resulting in a decrease in its crystallinity, a decrease in the melting point, and better tearability. However, when the content of acrylate monomers is too high, its cohesive strength will be too low, and problems such as the overall strength of the pipe becoming low will occur, affecting the forming and use of the pipe. Therefore, the acrylic acid content of 9wt% - 30wt% is better.

[0047] The melt index (MI) is an index representing the fluidity of the resin. The melt index is the mass in grams of the resin melt passing through a standard capillary in 10 minutes under certain temperature and pressure, and its unit is g / 10 min. A high melt index means a small average molecular weight of the resin, low viscosity, good fluidity, and easy processing and molding, but the mechanical properties are poor; a low melt index means a large average molecular weight of the resin, high viscosity, poor fluidity, and greater difficulty in molding processing, but the mechanical properties are good. In some embodiments, the melt index (MI) of the ethylene-acrylate copolymer is (0.5 - 10) g / 10 min, and the melt index within this range can meet better fluidity and better mechanical properties.

[0048] In some embodiments, the tear strength of the ethylene-acrylate copolymer is less than 75 kN / m, and the tear strength within this range is convenient for better tearing of the pipe.

[0049] In some embodiments, the tensile strength of the ethylene-acrylate copolymer is 15 - 24 Mpa, and the tensile strength within this range can further improve the tensile strength of the pipe.

[0050] In some embodiments, the polyethylene (PE) is low-density polyethylene (LDPE), and the melt index of the low-density polyethylene (LDPE) is (0.3 - 7) g / 10 min, and the tensile strength is 17 - 30 Mpa.

[0051] In some embodiments, the polyethylene (PE) is linear low-density polyethylene (LLDPE), and the melt index of the linear low-density polyethylene (LLDPE) is (0.3 - 10) g / 10 min, and the tensile strength is 20 - 35 Mpa.

[0052] In some embodiments, the polyethylene (PE) is medium density polyethylene (MDPE), and the medium density polyethylene (MDPE) has a melt index of (0.3 - 10) g / 10 min and a tensile strength of 25 - 35 Mpa.

[0053] In some embodiments, the polyethylene (PE) is high density polyethylene (HDPE), and the high density polyethylene (HDPE) has a melt index of (0.3 - 10) g / 10 min and a tensile strength of 28 - 40 Mpa.

[0054] In some embodiments, the polyolefin elastomer (POE) has a melt index in the range of (0.5 - 5) g / 10 min, a tensile strength of 18 - 40 Mpa, and a melting temperature of 70 - 110 °C.

[0055] In some embodiments, the ethylene - vinyl acetate copolymer (EVA) has a melt index of (0.5 - 7) g / 10 min, a tensile strength of 16 - 25 Mpa, and the vinyl acetate (VA) content does not exceed 20%.

[0056] In some embodiments, the materials for preparing the easily - peelable heat - shrinkable tube further include the following additives:

[0057] 0.05 - 0.3 parts of antioxidant;

[0058] 0.05 - 0.1 parts of lubricant;

[0059] In some embodiments, the antioxidant includes at least one of asymmetric hindered phenol antioxidants, aromatic amine antioxidants, thioether antioxidants, and phosphite antioxidants.

[0060] The hindered phenol antioxidants include at least one of antioxidant 1010 (pentaerythritol tetra [β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate]), BHT (2,6 - di - tert - butyl - p - cresol), and antioxidant 1076 (n - octadecyl β - (3,5 - di - tert - butyl - 4 - hydroxyphenyl) propionate);

[0061] The aromatic amine antioxidants include diphenylamine, p - phenylenediamine, and dihydroquinoline and their derivatives or polymers, such as antioxidant 445 (4,4’ - bis(α,α - dimethylbenzyl) diphenylamine).

[0062] The thioether antioxidants include at least one of DLTP (dilauryl thiodipropionate), DSTDP (distearyl thiodipropionate), and DSTP (octadecyl thiodipropionate);

[0063] The phosphite antioxidants include at least one of antioxidant 168 (tris[2,4-di-tert-butylphenyl]phosphite), antioxidant 618 (pentaerythritol bis(dioctadecyl phosphite)), and antioxidant 626 (bis[2,4-di-tert-butylphenyl]pentaerythritol diphosphite).

[0064] By adding antioxidants, it is beneficial to the antioxidant performance and aging resistance of the easily peelable heat shrinkable tube, and prolongs the service life of the easily peelable heat shrinkable tube.

[0065] In some embodiments, the lubricant includes at least one of PTFE powder, zinc stearate, magnesium stearate, silicone, calcium stearate, or ethylene bisstearamide. By adding the lubricant, it is beneficial to make the mixing of various raw materials more uniform.

[0066] In some embodiments, calculated by weight, the easily peelable heat shrinkable tube includes the following components:

[0067] Ethylene-acrylate copolymer: 20-90 parts, reinforcing agent: 10-80 parts. For example, the ethylene-acrylate copolymer can be any weight part within the range of 20-90 parts such as 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, 90 parts, etc.; the reinforcing agent can be any weight part within the range of 10-80 parts such as 10 parts, 20 parts, 30 parts, 40 parts, 50 parts, 60 parts, 70 parts, 80 parts, etc.

[0068] Under the limitation of the above weight parts, it is beneficial to promote the mixing of various raw materials, which not only meets the linear tearing performance but also achieves a certain strength.

[0069] The present invention also provides a preparation method for an easily peelable heat shrinkable tube, including the following steps:

[0070] Masterbatch processing: Mix the ethylene-acrylate copolymer and the reinforcing agent evenly according to the ratio, extrude, draw into strips, and cut into pellets through an extrusion device to obtain masterbatch pellets;

[0071] Extrusion into a tube: Extrude the masterbatch pellets obtained above through an extruder to obtain a semi-finished tube, wherein the orientation degree of the molecular chain of the extruded tube is controlled to be 40%-95%;

[0072] Irradiation process: Irradiate the above semi-finished tube through an irradiation device, and control the irradiation dose to be 100-300 kGy to obtain an irradiated tube;

[0073] Expansion molding: Expand the above irradiated tube at 130-260 °C, and then cool and shape it to obtain an easily peelable heat shrinkable tube; wherein, after the easily peelable heat shrinkable tube shrinks by more than 35% at 200 °C, the molecular chain orientation degree is 30%-85%.

[0074] In some embodiments, during the masterbatch processing step, when the ethylene-acrylate copolymer and the reinforcing agent are mixed, an antioxidant and a lubricant can also be added for mixing.

[0075] In some embodiments, during the masterbatch processing step, the mixing time is 3 - 5 min.

[0076] In some embodiments, during the masterbatch processing step, the extrusion temperature of the extrusion equipment is 130 - 200 °C.

[0077] In some embodiments, during the extrusion into a tube step, the degree of orientation of the molecular chains of the extruded tube is 50% - 90%.

[0078] In some embodiments, during the expansion molding step, cooling and shaping are performed to obtain an easily peelable heat shrinkable tube. Among them, after the easily peelable heat shrinkable tube shrinks by more than 35% at a temperature of 200 °C, the degree of molecular chain orientation is 40% - 85%.

[0079] In some embodiments, during the extrusion process, the degree of orientation of the molecular chains of the extruded tube is controlled to be 50% - 90%. After the easily peelable heat shrinkable tube has a shrinkage rate of more than 35% when heated at a temperature of 200 °C, the degree of molecular chain orientation of the easily peelable heat shrinkable tube is 40% - 85%. The degree of orientation in these two ranges makes the linear tear performance of the prepared easily peelable heat shrinkable tube more excellent.

[0080] The degree of orientation of the easily peelable heat shrinkable tube not only depends on the extrusion process but is also affected by the irradiation process. During the extrusion process, generally by controlling the traction speed and the extrusion speed, tubes with different draw ratios are obtained. By controlling the draw ratio of the extruded tube to be between 9 and 30, an extruded tube with a molecular chain orientation degree of 40% - 95% is obtained. After the extruded tube undergoes the irradiation process, by controlling the irradiation dose to be 100 - 300 kGy, the extruded tube can be changed from an ordinary two-dimensional linear molecular structure to a three-dimensional network molecular structure after irradiation, obtaining an appropriate crosslinking degree. Finally, after the easily peelable heat shrinkable tube shrinks by more than 35% at a temperature of 200 °C, the degree of molecular chain orientation of the easily peelable heat shrinkable tube is 30% - 85%, having the performance of being tearable at room temperature. Of course, the tearable performance of the easily peelable heat shrinkable tube can also be achieved by adding a crosslinking agent to the mixture of ethylene-acrylate copolymer and reinforcing agent and then adjusting the irradiation dose during the irradiation process. The irradiation equipment can be an electron accelerator irradiation device, a radioactive isotope irradiation device, which is not limited here.

[0081] The easily peelable heat shrinkable tube of the present invention has heat shrinkability and tearability, so it can be tightly attached to the object to be attached, generating a tightening force on the object to be attached. The magnitude of the tightening force is related to the shrinkage rate of the heat shrinkable tube. The larger the shrinkage rate, the greater the tightening force; the smaller the shrinkage rate, the smaller the tightening force. Due to the radiation crosslinkability of ethylene-acrylate copolymer, the crosslinking degree of the extruded tube can be controlled through the radiation process, changing its ordinary two-dimensional linear molecular structure into a three-dimensional network molecular structure. The three-dimensional network molecular structure plays a role in solidifying the orientation of the internal molecular chains in the ethylene-acrylate copolymer during the extrusion process. Further, by controlling the radiation dose to control the crosslinking degree of the blend during the radiation process, the molecular chain orientation degree of the obtained easily peelable heat shrinkable tube reaches 30%-85% after shrinking by more than 35% at 200°C, thus realizing the tearable performance of the heat shrinkable tube. While FEP material is not radiation-resistant, and the long linear macromolecules between FEP materials cannot form a network structure through radiation, which is the reason for the difference in shrinkage rate between the two; and by controlling the molecular chain orientation degree of the extruded tube to 40%-95% through the extrusion process, manufacturing the heat shrinkable tube by the radiation process, and controlling the orientation degree of the final heat shrinkable tube, this is the difference in adjusting the tear performance between the two. In addition, the glass transition temperature (Tg) and melting point of ethylene-acrylate copolymer are lower compared with those of the fluororesin substrate, which also makes the use shrinkage temperature of the easily peelable heat shrinkable tube of ethylene-acrylate copolymer lower than that of the fluorine substrate.

[0082] In some embodiments, the lowest shrinkage temperature of the easily peelable heat shrinkable tube can reach 70°C, and complete shrinkage can be achieved at 110°C, with a low shrinkage temperature.

[0083] In some embodiments, at 110°C, the shrinkage ratio of the easily peelable heat shrinkable tube is 1.3 - 4.5.

[0084] It can be seen that the easily peelable heat shrinkable tube provided by the present invention has a low shrinkage temperature and a high shrinkage rate, and is suitable for assisting the shrinkage of high-molecular non-shrinkable tubes with a large shrinkage ratio. In addition, the addition of the reinforcing agent can also improve the tensile strength of the easily peelable heat shrinkable tube.

[0085] The technical solution of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not used to limit the present invention.

[0086] Measurement of orientation degree

[0087] A single-screw extruder is used, and the specifications of its extrusion die are as follows: the die orifice is D1 (mm), the mandrel is D2 (mm), and the dimensions of the extruded pipe are as follows: the inner diameter of the extrusion is d1 (mm), and the pipe with a wall thickness of w (mm) (depending on the dimensions of the extruded pipe, the corresponding type of extruder, die orifice, and mandrel must be selected). During the extrusion process, by controlling the traction speed and extrusion speed, pipes with different draw ratios are obtained. The formula for calculating the draw ratio is as follows:

[0088]

[0089] The orientation degree of the molecular chains of the extruded pipe was studied by X-ray diffraction (D / Max-rA type rotating anode X-ray diffractometer). After the heat-shrinkable tube was completely shrunk, the orientation degree of the molecular chains was calculated using the following formula:

[0090]

[0091] П is the orientation degree, and H is the angle of the distribution of the diffraction along one diffraction arc of the equatorial diffraction. During the measurement, the half-width of the intensity distribution, that is, half of the maximum intensity on the arc segment, is used as the starting and ending points of the arc segment.

[0092] Test of tear linearity

[0093] To more clearly judge the tear linearity, the following method was used for measurement. A cut with a length of 40 mm was set at one end of a 1000-mm-long specimen. The cut was set parallel to the length direction of the pipe at the center of the pipe using a fixture. The pipe was torn from the cut part to the other end at a speed of 200 mm / min. The weights of the two torn pipes were measured respectively, and the ratio of the weights was calculated. It can be judged that the closer the ratio is to 50%:50%, the higher the tear linearity.

[0094] Tear strength test

[0095] After a 40-mm cut was formed by cutting with a tool, a 100-mm sample was taken and torn at a speed of 200 mm / min through a tensile testing machine, and the maximum force at that time was measured as the tear strength. The same composition of samples was measured 3 times, and the weighted average value was calculated.

[0096] Tensile strength test

[0097] The test was carried out with reference to the method in UL 224 - 2021, 5.4.

[0098] Determination of the complete shrinkage temperature

[0099] Take a 100-mm sample and heat the sample in a programmed-temperature oven. With 50 °C as the starting shrinkage temperature, increase the oven temperature by 10 °C every 3 minutes, so that the sample shrinks for 3 minutes at each temperature. Record the shrinkage temperature until, after three consecutive measurements, the inner diameter after shrinkage does not change. Then, the temperature recorded for the first time among the three consecutive measurements is the complete shrinkage temperature.

[0100] Measurement of shrinkage rate

[0101] Take a 100-mm sample and shrink it for 3 minutes at 200 °C. Measure the inner diameter of the sample before and after shrinkage. Calculate according to the following formula: Shrinkage rate = (Inner diameter before shrinkage - Inner diameter after shrinkage) / Inner diameter before shrinkage × 100%

[0102] Example 1

[0103] Masterbatch processing

[0104] Mix ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218), low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K), and antioxidant (antioxidant 1010) in a mass ratio of 60 / 10 / 0.1, and add them to a high-speed mixer and stir for 3 - 5 minutes. Feed the material obtained above into a twin-screw extruder with a diameter of 30 mm, and extrude at a screw speed of 45 rpm and a temperature of 130 - 200 °C, then draw into strands, cool with water, and pelletize to finally form masterbatch particles.

[0105] Extruding pipes

[0106] Use the masterbatch particles obtained above to form pipes with a single-screw extruder. Use a full-thread screw, and control the molecular chain orientation degree of the extruded pipe at 50% at a screw speed of 5 - 45 rpm and a die temperature of 130 - 190 °C, and then extrude and mold. Obtain a semi-finished sleeve with an inner diameter of 0.5 mm, an outer diameter of 0.9 mm, and a wall thickness of 0.2 mm.

[0107] Irradiation crosslinking

[0108] Irradiate the above semi-finished sleeve with an electron accelerator device at an irradiation dose of 200 kGy for irradiation crosslinking.

[0109] Expanding pipes

[0110] Expand the above irradiated and crosslinked pipes 2 times with an expansion device at 130 - 260 °C; then cool and shape them to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature is 110 °C, the shrinkage rate is 50%, and the molecular chain orientation degree after complete shrinkage is 44%.

[0111] Example 2

[0112] Masterbatch processing

[0113] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was replaced with ethylene-ethyl acrylate copolymer (EEA, ELVALOY TM AC 2116) / low density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, the production was carried out in the same manner as in Example 1.

[0114] Extruding pipes

[0115] The semi-forming was carried out in the same manner as in Example 1.

[0116] Irradiation crosslinking

[0117] The irradiation was carried out in the same manner as in Example 1.

[0118] Expanding pipes

[0119] The expansion molding was carried out in the same manner as in Example 1, and a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm was obtained. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 43%.

[0120] Example 3

[0121] Masterbatch processing

[0122] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was replaced with ethylene-butyl acrylate copolymer (EBA, AC 3717) / low density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, the production was carried out in the same manner as in Example 1.

[0123] Extruding pipes

[0124] The semi-forming was carried out in the same manner as in Example 1.

[0125] Irradiation crosslinking

[0126] Irradiation was carried out in the same manner as in Example 1.

[0127] Expanded tubing

[0128] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 45%.

[0129] Example 4

[0130] Masterbatch processing

[0131] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was replaced with ethylene-methyl methacrylate copolymer (EMMA, Sumitomo CM8014) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, the production was carried out in the same manner as in Example 1.

[0132] Extruded tubing

[0133] Semi-forming was carried out in the same manner as in Example 1.

[0134] Irradiation crosslinking

[0135] Irradiation was carried out in the same manner as in Example 1.

[0136] Expanded tubing

[0137] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 44%.

[0138] Example 5

[0139] Masterbatch processing

[0140] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TMEthylene - methyl acrylate copolymer (EMA, DuPont ELVALOY) was substituted for ethylene - vinyl acetate copolymer (EVA, AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 TM Ethylene - vinyl acetate copolymer (EVA, AC 1218) / linear low - density polyethylene (LLDPE, LLDPE 218W) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, and the production was carried out in the same manner as in Example 1.

[0141] Extruded pipe

[0142] Semi - forming was carried out in the same manner as in Example 1.

[0143] Irradiation cross - linking

[0144] Irradiation was carried out in the same manner as in Example 1.

[0145] Expanded pipe

[0146] Expansion molding was carried out in the same manner as in Example 1, and a heat - shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm was obtained. The complete shrinkage temperature was 120 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 44%.

[0147] Example 6

[0148] Masterbatch processing

[0149] Except that ethylene - methyl acrylate copolymer (EMA, DuPont ELVALOY) was substituted for ethylene - vinyl acetate copolymer (EVA, AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 TM Ethylene - methyl acrylate copolymer (EMA, DuPont ELVALOY) was substituted for ethylene - vinyl acetate copolymer (EVA, AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 TM Ethylene - vinyl acetate copolymer (EVA, AC 1218) / medium - density polyethylene (MDPE, DOWAXELERON TM 8864NT) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, and the production was carried out in the same manner as in Example 1.

[0150] Extruded pipe

[0151] Semi - forming was carried out in the same manner as in Example 1.

[0152] Irradiation cross - linking

[0153] Irradiation was carried out in the same manner as in Example 1.

[0154] Expanded tubing

[0155] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 130 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 43%.

[0156] Example 7

[0157] Masterbatch processing

[0158] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / high-density polyethylene (HDPE, lyondellbasell ACP 6541A) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, the production was carried out in the same manner as in Example 1.

[0159] Extruded tubing

[0160] Semi-forming was carried out in the same manner as in Example 1.

[0161] Irradiation crosslinking

[0162] Irradiation was carried out in the same manner as in Example 1.

[0163] Expanded tubing

[0164] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 130 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 43%.

[0165] Example 8

[0166] Masterbatch processing

[0167] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasellLupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TMAC 1218) / Polyolefin elastomer (POE, ENGAGE TM 8480) / Antioxidant (Antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, and the production was carried out in the same manner as in Example 1.

[0168] Extruded pipe

[0169] Semi-forming was carried out in the same manner as in Example 1.

[0170] Irradiation crosslinking

[0171] Irradiation was carried out in the same manner as in Example 1.

[0172] Expanded pipe

[0173] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 44%.

[0174] Example 9

[0175] Masterbatch processing

[0176] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / Low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / Antioxidant (Antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was replaced with ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / Ethylene-vinyl acetate copolymer (EVA, 7350M) / Antioxidant (Antioxidant 1010) (mass ratio) = 60 / 10 / 0.1, and the production was carried out in the same manner as in Example 1.

[0177] Extruded pipe

[0178] Semi-forming was carried out in the same manner as in Example 1.

[0179] Irradiation crosslinking

[0180] Irradiation was carried out in the same manner as in Example 1.

[0181] Expanded pipe

[0182] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 45%.

[0183] Example 10

[0184] Masterbatch processing

[0185] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (Antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (Antioxidant 1010) (mass ratio) = 20 / 10 / 0.1, it was manufactured in the same manner as in Example 1.

[0186] Extruding tubes

[0187] Semi-forming was carried out in the same manner as in Example 1.

[0188] Irradiation crosslinking

[0189] Irradiation was carried out in the same manner as in Example 1.

[0190] Expanding tubes

[0191] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110°C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 44%.

[0192] Example 11

[0193] Masterbatch processing

[0194] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (Antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (Antioxidant 1010) (mass ratio) = 75 / 10 / 0.1, it was manufactured in the same manner as in Example 1.

[0195] Extruding tubes

[0196] The semi-forming was carried out in the same manner as in Example 1.

[0197] Irradiation crosslinking

[0198] The irradiation was carried out in the same manner as in Example 1.

[0199] Expanded tubing

[0200] The expansion molding was carried out in the same manner as in Example 1, and a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm was obtained. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 45%.

[0201] Example 12

[0202] Masterbatch processing

[0203] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 90 / 10 / 0.1, the production was carried out in the same manner as in Example 1.

[0204] Extruded tubing

[0205] The semi-forming was carried out in the same manner as in Example 1.

[0206] Irradiation crosslinking

[0207] The irradiation was carried out in the same manner as in Example 1.

[0208] Expanded tubing

[0209] The expansion molding was carried out in the same manner as in Example 1, and a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm was obtained. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 45%.

[0210] Example 13

[0211] Masterbatch processing

[0212] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TMEthylene - methyl acrylate copolymer (EMA, DuPont ELVALOY replaced ethylene - acrylic acid copolymer (AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 TM Except for ethylene - acrylic acid copolymer (AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 40 / 0.1, it was manufactured in the same manner as in Example 1.

[0213] Extruded pipe

[0214] Semi - forming was carried out in the same manner as in Example 1.

[0215] Irradiation cross - linking

[0216] Irradiation was carried out in the same manner as in Example 1.

[0217] Expanded pipe

[0218] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat - shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 44%.

[0219] Example 14

[0220] Masterbatch processing

[0221] Except for replacing ethylene - acrylic acid copolymer (AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 with ethylene - methyl acrylate copolymer (EMA, DuPont ELVALOY TM Ethylene - methyl acrylate copolymer (EMA, DuPont ELVALOY replaced ethylene - acrylic acid copolymer (AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 TM Except for ethylene - acrylic acid copolymer (AC 1218) / low - density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 60 / 0.1, it was manufactured in the same manner as in Example 1.

[0222] Extruded pipe

[0223] Semi - forming was carried out in the same manner as in Example 1.

[0224] Irradiation cross - linking

[0225] Irradiation was carried out in the same manner as in Example 1.

[0226] Expanded pipe

[0227] The expansion molding was carried out in the same manner as in Example 1, and a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm was obtained. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 44%.

[0228] Example 15

[0229] Masterbatch processing

[0230] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 80 / 0.1, the manufacturing was carried out in the same manner as in Example 1.

[0231] Extruded pipe

[0232] The semi-forming was carried out in the same manner as in Example 1.

[0233] Irradiation crosslinking

[0234] The irradiation was carried out in the same manner as in Example 1.

[0235] Expanded pipe

[0236] The expansion molding was carried out in the same manner as in Example 1, and a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm was obtained. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 43%.

[0237] Example 16

[0238] Masterbatch processing

[0239] The manufacturing was carried out in the same manner as in Example 1.

[0240] Extruded pipe

[0241] Except that the degree of molecular chain orientation of the extruded pipe was controlled at 40%, the molding was carried out in the same manner as in Example 1.

[0242] Irradiation crosslinking

[0243] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was changed to 190 KGy.

[0244] Expanded tubing

[0245] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 35%.

[0246] Example 17

[0247] Masterbatch processing

[0248] Manufacture was carried out in the same manner as in Example 1.

[0249] Extruded tubing

[0250] Molding was carried out in the same manner as in Example 1, except that the degree of molecular chain orientation of the extruded tubing was controlled at 70%.

[0251] Irradiation crosslinking

[0252] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was changed to 160 KGy.

[0253] Expanded tubing

[0254] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 64%.

[0255] Example 18

[0256] Masterbatch processing

[0257] Manufacture was carried out in the same manner as in Example 1.

[0258] Extruded tubing

[0259] Molding was carried out in the same manner as in Example 1, except that the degree of molecular chain orientation of the extruded tubing was controlled at 90%.

[0260] Irradiation crosslinking

[0261] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was changed to 170 KGy.

[0262] Expanded tubing

[0263] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 82%.

[0264] Example 19

[0265] Masterbatch processing

[0266] Manufacture was carried out in the same manner as in Example 1.

[0267] Extrusion of tubing

[0268] Molding was carried out in the same manner as in Example 1, except that the degree of molecular chain orientation of the extruded tubing was controlled at 95%.

[0269] Irradiation crosslinking

[0270] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was changed to 190 KGy.

[0271] Expansion of tubing

[0272] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 85%.

[0273] Example 20

[0274] Masterbatch processing

[0275] Manufacture was carried out in the same manner as in Example 1.

[0276] Extrusion of tubing

[0277] Semi-molding was carried out in the same manner as in Example 1.

[0278] Irradiation crosslinking

[0279] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled at 100 KGy.

[0280] Expansion of tubing

[0281] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 40%.

[0282] Example 21

[0283] Masterbatch processing

[0284] Manufacture was carried out in the same manner as in Example 1.

[0285] Extruded pipe

[0286] Semi-forming was carried out in the same manner as in Example 1.

[0287] Irradiation crosslinking

[0288] The above semi-finished casing was irradiated with cobalt-60 (Co) with a controlled irradiation dose of 300 KGy, and irradiation was carried out in the same manner as in Example 1.

[0289] Expanded pipe

[0290] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 47%.

[0291] Example 22

[0292] Masterbatch processing

[0293] Manufacture was carried out in the same manner as in Example 1.

[0294] Extruded pipe

[0295] Semi-forming was carried out in the same manner as in Example 1.

[0296] Irradiation crosslinking

[0297] Irradiation was carried out in the same manner as in Example 1.

[0298] Expanded pipe

[0299] The pressure of nitrogen gas filled into the expansion equipment and the die size were changed, and expansion was carried out in the same manner as in Example 1 to obtain a heat-shrinkable tube with an inner diameter of 0.77 mm, an outer diameter of 1.13 mm, and a wall thickness of 0.18 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 35%, and the molecular chain orientation degree after complete shrinkage was 44%.

[0300] Example 23

[0301] Masterbatch processing

[0302] Manufacture was carried out in the same manner as in Example 1.

[0303] Extruded pipe

[0304] Semi-forming was carried out in the same manner as in Example 1.

[0305] Irradiation crosslinking

[0306] Irradiation was carried out in the same manner as in Example 1.

[0307] Expanded pipe

[0308] The pressure of nitrogen gas filled into the expansion equipment and the die size were changed, and the expansion was carried out in the same manner as in Example 1, obtaining a heat shrinkable tube with an inner diameter of 2 mm, an outer diameter of 2.2 mm, and a wall thickness of 0.1 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 75%, and the molecular chain orientation degree after complete shrinkage was 44%.

[0309] Comparative Example 1

[0310] Masterbatch processing

[0311] Low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 0.1 was added to a high-speed mixer and stirred for 3 - 5 minutes. The material obtained from the above process was put into a twin-screw extruder with a barrel diameter of 30 mm, and extruded at a screw rotation speed of 45 rpm and a die temperature of 130 - 200 °C, then strand pelletized and water-cooled to finally form masterbatch particles.

[0312] Extruded pipe

[0313] The masterbatch particles obtained above were used to form a pipe by means of a single-screw extruder. A full-thread screw was used, and at a screw rotation speed of 10 - 30 rpm and a die temperature of 130 - 190 °C, the molecular chain orientation degree of the extruded pipe was controlled at 50% and extrusion molding was carried out. A pipe with an inner diameter of 0.5 mm, an outer diameter of 0.9 mm, and a wall thickness of 0.2 mm was obtained.

[0314] Irradiation crosslinking

[0315] The above semi-finished casing was irradiated using an electron accelerator device with an irradiation dose of 200 KGy for irradiation crosslinking.

[0316] Expanded pipe

[0317] The above irradiated crosslinked pipe was filled with nitrogen gas into the expansion equipment at 130 - 260 °C to expand the pipe; then it was cooled and shaped, obtaining a heat shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 120 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 43%.

[0318] Comparative Example 2

[0319] Masterbatch processing

[0320] Except that the low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 0.1 was replaced with polyolefin elastomer (POE, ENGAGETM Except that the ratio of low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) was changed to 60 / 0.1, it was manufactured in the same manner as Comparative Example 1.

[0321] Extruded pipe

[0322] It was molded in the same manner as Comparative Example 1.

[0323] Irradiation crosslinking

[0324] It was irradiated in the same manner as Comparative Example 1.

[0325] Expanded pipe

[0326] It was expanded and molded in the same manner as Comparative Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 100 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 45%.

[0327] Comparative Example 3

[0328] Masterbatch processing

[0329] Except that the ratio of ethylene-vinyl acetate copolymer (EVA, 7350M) / antioxidant (antioxidant 1010) (mass ratio) was changed to 60 / 0.1, it was manufactured in the same manner as Comparative Example 1.

[0330] Extruded pipe

[0331] It was molded in the same manner as Comparative Example 1.

[0332] Irradiation crosslinking

[0333] It was irradiated in the same manner as Comparative Example 1.

[0334] Expanded pipe

[0335] It was expanded and molded in the same manner as Comparative Example 1 to obtain a heat-shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 45%.

[0336] Comparative Example 4

[0337] Masterbatch processing

[0338] Except that ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TMAC 1218) / Low Density Polyethylene (LDPE, lyondellbasell Lupolen 2426K) / Antioxidant (Antioxidant 1010) (mass ratio) = 60 / 10 / 0.1 was replaced with Ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM Except that the molecular chain orientation degree of the extruded pipe was controlled at 0.1 (mass ratio) = 60 / 0.1, the manufacturing was carried out in the same manner as in Example 1.

[0339] Extruded pipe

[0340] The molding was carried out in the same manner as in Example 1.

[0341] Irradiation crosslinking

[0342] The irradiation was carried out in the same manner as in Example 1.

[0343] Expanded pipe

[0344] The expansion molding was carried out in the same manner as in Example 1 to obtain a heat shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 45%.

[0345] Comparative Example 5

[0346] Masterbatch processing

[0347] The manufacturing was carried out in the same manner as in Example 1.

[0348] Extruded pipe

[0349] Except that the molecular chain orientation degree of the extruded pipe was controlled at 15%, the molding was carried out in the same manner as in Example 1.

[0350] Irradiation crosslinking

[0351] The irradiation was carried out in the same manner as in Example 1.

[0352] Expanded pipe

[0353] The expansion molding was carried out in the same manner as in Example 1 to obtain a heat shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the molecular chain orientation degree after complete shrinkage was 10%.

[0354] Comparative Example 6

[0355] Masterbatch processing

[0356] The manufacturing was carried out in the same manner as in Example 1.

[0357] Extruded pipe

[0358] Manufacture was carried out in the same manner as in Example 1.

[0359] Irradiation crosslinking

[0360] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled to be 50 KGy.

[0361] Expanded tubing

[0362] Expansion molding was carried out in the same manner as in Example 1 to obtain a heat shrinkable tube with an inner diameter of 1.0 mm, an outer diameter of 1.3 mm, and a wall thickness of 0.15 mm. The complete shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after complete shrinkage was 20%.

[0363] Comparative Example 7

[0364] A commercially available tearable FEP heat shrinkable tube was used, with a shrinkage ratio of 37.5%, an inner diameter of 1.12 mm before shrinkage, and an inner diameter of 0.7 mm after shrinkage.

[0365] For the easily peelable heat shrinkable tube prepared above, the preparation condition parameters of Examples 1-23 are shown in Table 1, and the preparation condition parameters of Comparative Examples 1-7 are shown in Table 2. Control the degree of molecular chain orientation of the extruded tubing according to the above measurement method of the degree of orientation, and measure the degree of molecular chain orientation after complete shrinkage of the prepared heat shrinkable tube; measure the tear linearity according to the above test method of tear linearity; measure the tear strength according to the above test method of tear strength; measure the tensile strength according to the above test method of tensile strength; measure the complete shrinkage temperature according to the above measurement method of complete shrinkage temperature; measure the shrinkage rate according to the above measurement method of shrinkage rate. The measurement results of Examples 1-23 and Comparative Examples 1-7 are shown in Table 3.

[0366] Table 1 Preparation condition parameters of Examples 1-23

[0367]

[0368]

[0369]

[0370] Table 2 Preparation condition parameters of Comparative Examples 1-7

[0371]

[0372]

[0373] Table 3 Measurement results of Examples 1-23 and Comparative Examples 1-7

[0374]

[0375]

[0376] It can be seen from Examples 1-4 and Comparative Examples 1-3 that the type of polymer has a great relationship with the easily peelable heat-shrinkable tube made of polyolefin and its copolymer resin. Only a specific ethylene-acrylate copolymer can be used to prepare the easily peelable heat-shrinkable tube. It can be seen from Examples 1, 16-19 and Comparative Example 5 that in addition to the type of polymer, the degree of orientation in the extrusion process needs to be controlled at 40%-95%. At the same time, it can be seen from Examples 1, 20-21 and Comparative Example 6 that the irradiation dose needs to be controlled to obtain an appropriate degree of crosslinking, and finally the degree of orientation of the prepared easily peelable heat-shrinkable tube is 30%-85%, having a straight-line tear property. It can be seen from Example 1 and Comparative Example 4 that the addition of a reinforcing agent can increase the tensile strength of the easily peelable heat-shrinkable tube. It can be seen from Examples 1-23 and Comparative Example 7 that the easily peelable heat-shrinkable tube provided by the present invention has a lower shrinkage temperature, a higher shrinkage rate compared with the FEP heat-shrinkable tube, and is suitable for assisting the shrinkage of large magnification non-shrinkable polymer pipes.

[0377] The present invention provides an easily peelable heat-shrinkable tube made of polyolefin and its copolymer resin and a reinforcing agent. Its tear strength is lower than that of the FEP easily peelable heat-shrinkable tube, the shrinkage temperature is low, the shrinkage rate is high, the tensile strength is relatively high, and there is no adhesion to the internal material. It can completely replace the FEP easily peelable heat-shrinkable tube, providing a new choice for the easily peelable heat-shrinkable tube.

[0378] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent structure or equivalent process transformation made by using the content of the specification of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. An easily peelable heat shrinkable tube having linear tearability in the longitudinal direction of the tube, characterized in that, Calculated by weight parts, the preparation materials of the easily peelable heat shrinkable tube include the following components: Ethylene-acrylate copolymer: 20-90 parts; Reinforcing agent: 10-80 parts.

2. The peelable heat shrinkable tube according to claim 1, wherein The ethylene-acrylate copolymer includes at least one of ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), and ethylene-methyl methacrylate copolymer (EMMA).

3. The easily peelable heat-shrinkable tube according to claim 1, wherein The reinforcing agent includes at least one of polyethylene (PE), polyolefin elastomer (POE), and ethylene-vinyl acetate copolymer (EVA).

4. The easily peelable heat shrinkable tube according to claim 1, wherein, The ethylene-acrylate copolymer has a melt index of (0.5-10) g / 10 min and an acrylic acid content of 9 wt%-30 wt%; Or, the tear strength of the ethylene-acrylate copolymer is lower than 75 kN / m; Or, the tensile strength of the ethylene-acrylate copolymer is 15-24 Mpa.

5. The peelable heat shrinkable tube according to claim 3, wherein The polyethylene (PE) is low-density polyethylene (LDPE), and the low-density polyethylene (LDPE) has a melt index of (0.3-7) g / 10 min and a tensile strength of 17-30 Mpa; Or, the polyethylene (PE) is linear low-density polyethylene (LLDPE), and the linear low-density polyethylene (LLDPE) has a melt index of (0.3-10) g / 10 min and a tensile strength of 20-35 Mpa; Or, the polyethylene (PE) is medium-density polyethylene (MDPE), and the medium-density polyethylene (MDPE) has a melt index of (0.3-10) g / 10 min and a tensile strength of 25-35 Mpa; Or, the polyethylene (PE) is high-density polyethylene (HDPE), and the high-density polyethylene (HDPE) has a melt index of (0.3-10) g / 10 min and a tensile strength of 28-40 Mpa.

6. The easily peelable heat-shrinkable tube according to claim 3, wherein The polyolefin elastomer (POE) has a melt index of (0.5-5) g / 10 min, a tensile strength of 18-40 Mpa, and a melting temperature of 70-110 °C.

7. The peelable heat shrinkable tube according to claim 3, wherein The ethylene-vinyl acetate copolymer (EVA) has a melt index of (0.5-7) g / 10 min, a tensile strength of 16-25 Mpa, and the vinyl acetate (VA) content does not exceed 20%.

8. The easily peelable heat-shrinkable tube according to claim 1, characterized in that, Calculated by weight parts, the preparation materials of the easily peelable heat shrinkable tube further include the following additives: Antioxidant: 0.05-0.3 parts; Lubricant: 0.05-0.1 parts; Among them, the antioxidant includes at least one of asymmetric hindered phenol antioxidants, aromatic amine antioxidants, thioether antioxidants, and phosphite antioxidants; The lubricant includes at least one of FEP powder, zinc stearate, magnesium stearate, silicone, calcium stearate, or ethylene bisstearamide.

9. A preparation method of an easily peelable heat shrinkable tube, characterized in that, Including the following steps: Masterbatch processing: Mix the ethylene-acrylate copolymer and the reinforcing agent evenly according to the ratio, extrude, draw into strips, and cut into pellets through an extrusion device to obtain masterbatch pellets; Extrusion into a tube: Extrude the masterbatch pellets obtained above through an extruder to obtain a semi-finished tube, wherein the orientation degree of the molecular chain of the extruded tube is controlled to be 40%-95%; Irradiation process: irradiate the above-mentioned semi-finished pipe through an irradiation device, control the irradiation dose to be 100-300 KGy, and obtain the irradiated pipe; Expansion molding: expand the above-mentioned irradiated pipe at 130-260 °C, and then cool and shape it to obtain an easily peelable heat shrinkable tube; wherein, after the easily peelable heat shrinkable tube shrinks by more than 35% at a temperature of 200 °C, the molecular chain orientation degree is 30%-85%.

10. The preparation method according to claim 9, characterized in that, In the masterbatch processing step, when the ethylene-acrylate copolymer and the reinforcing agent are mixed, an antioxidant and a lubricant can also be added for mixing; Or, in the masterbatch processing step, the mixing time is 3-5 min; Or, in the masterbatch processing step, the extrusion temperature of the extrusion equipment is 130-200 °C; Or, in the extruding into a tube step, the orientation degree of the molecular chain of the extruded tube is 50%-90%; Or, in the expansion molding step, cool and shape it to obtain an easily peelable heat shrinkable tube, wherein, after the easily peelable heat shrinkable tube shrinks by more than 35% at a temperature of 200 °C, the molecular chain orientation degree is 40%-85%.

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