Easily stripped heat shrink tube

Abstract

The invention discloses an easy-to-peel heat shrink tube, which adopts an ethylene-acrylate copolymer as matrix resin, 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. The cohesion strength of an ethylene-acrylate molecular chain is reduced; furthermore, the orientation degree of an internal molecular chain of the ethylene-acrylate copolymer of the extruded pipe is controlled through an extrusion process, and the orientation degree is ensured to be in a range of 40%-95%, so that the molecular chain and a chain segment of the ethylene-acrylate copolymer extend from a freely curled disordered state to an orientation direction, and the entangled structure of molecules is further reduced; furthermore, after the easy-to-peel heat-shrinkable tube shrinks by more than 35% at the temperature of 200 DEG C, the molecular chain orientation degree of the easy-to-peel heat-shrinkable tube is 30-85%, and the normal-temperature tearable performance of the easy-to-peel heat-shrinkable tube is realized.

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. 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 after the auxiliary shrinkage is completed without using mechanical removal (operations such as knife cutting, scratching, cutting, grinding, etc. will cause defects or damage to the internal material). After removing the easily peelable heat shrinkable tube, the surface of the non-shrinkable polymer tube is smooth without defects or residues.

[0003] Currently, the commonly available room-temperature tearable heat shrinkable tubes in 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, which has a low tear 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 purpose, the present invention provides an easily peelable heat shrinkable tube, which has linear tearability in the length direction of the tube. The preparation material of the easily peelable heat shrinkable tube includes ethylene-acrylate copolymer as the matrix resin, and the extrusion process controls the molecular chain orientation degree of the extruded tube to be 40%-95%. The shrinkage rate of the easily peelable heat shrinkable tube when heated at 200°C is more than 35%. After shrinking by more than 35% at 200°C, the molecular chain orientation degree of the easily peelable heat shrinkable tube is 30%-85%.

[0006] In some embodiments of the present application, the extrusion process controls the molecular chain orientation degree of the extruded tube to be 50%-90%. The shrinkage rate of the easily peelable heat shrinkable tube when heated at 200°C is more than 35%. After shrinking by more than 35% at 200°C, the molecular chain orientation degree of the easily peelable heat shrinkable tube is 40%-85%.

[0007] In some embodiments of the present application, after the extrusion process, there is also an irradiation process, and the irradiation dose provided by the irradiation equipment in the irradiation process is 100-300KGy.

[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 melt index of the ethylene-acrylate copolymer is (0.5 - 10) g / 10min, and the acrylic acid content is 9wt% - 30wt%.

[0010] In some embodiments of the present application, the tear strength of the ethylene-acrylate copolymer is less than 75 kN / m.

[0011] In some embodiments of the present application, the tensile strength of the ethylene-acrylate copolymer is 15 - 24 Mpa.

[0012] In some embodiments of the present application, the ratio representing the tear linearity is in the range of 50%:50% to 48%:52%.

[0013] In some embodiments of the present application, the inner diameter of the easily peelable heat-shrinkable tube is 0.3 - 16 mm.

[0014] In some embodiments of the present application, the wall thickness of the easily peelable heat-shrinkable tube is 0.1 - 2 mm.

[0015] Beneficial effects that the present invention can achieve:

[0016] For the easily peelable heat-shrinkable tube of the present invention, an ethylene-acrylate copolymer is used as the matrix resin. Since ethylene-acrylate is a copolymer and contains acrylate side groups, its crystallization is disrupted, the distance between the main-chain vinyl molecules is increased, and the structure of molecular entanglement is reduced, resulting in a decrease in the cohesive strength of the ethylene-acrylate molecular chains. Further, by controlling the orientation degree of the internal molecular chains of the ethylene-acrylate copolymer in the extruded tube during the extrusion process, ensuring that the orientation degree is in the range of 40% - 95%, the ethylene-acrylate copolymer molecular chains and segments are stretched from the disordered state of free curling to the orientation direction, further reducing the structure of molecular entanglement. Still further, after the easily peelable heat-shrinkable tube shrinks by more than 35% at a temperature of 200°C, the molecular chain orientation degree of the easily peelable heat-shrinkable tube is 30% - 85%, realizing the room-temperature tearable performance of the easily peelable heat-shrinkable tube. Specific embodiments

[0017] 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.

[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0019] In the present invention, descriptions such as "first" and "second" are only for descriptive purposes and cannot be construed as indicating or implying their relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one such feature. Additionally, the technical solutions between various embodiments can be combined with each other, but it must be based on the ability of those of ordinary skill in the art to implement. When the combination of technical solutions results in contradictions or cannot be implemented, it should be considered that such a combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0020] The polymer orientation structure refers to a structure in which molecular chains or other structural units are preferentially arranged along the direction of an external force and frozen under the action of a certain external force. After the melt-extruded ethylene-acrylate copolymer undergoes an extrusion and stretching process, the molecular chains of the ethylene-acrylate copolymer are arranged along the stretching direction, that is, preferentially oriented along the stretching direction.

[0021] The ethylene-acrylate copolymer is copolymerized from ethylene and 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 the ethylene-acrylate copolymer are related to the content of acrylate monomers, average molecular weight, molecular weight distribution, long branched chains, and short branched chains.

[0022] Polymeric materials exist in a state where the molecular chains that make them up are entangled like wool balls. In a molded article formed using a polymeric material, the state of entanglement 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 molecular chain orientation of the extruded pipe is maintained within a certain range during the extrusion process, a peelable pipe with linear tearability in the longitudinal direction of the pipe can be prepared. This may be due to the special structure of ethylene-acrylate copolymer, which contains side groups such as methyl acrylate, ethyl acrylate, butyl acrylate, and methyl methacrylate, affecting molecular crystallization and molecular entanglement, increasing the distance between the main-chain molecules, reducing the structure of molecular entanglement, and causing a decrease in the cohesive strength of the ethylene-acrylate copolymer molecular chains. Further, by controlling the degree of orientation of the internal molecular chains of the ethylene-acrylate copolymer during the extrusion process and ensuring that the degree of orientation is within a certain range, the ethylene-acrylate copolymer molecular chains and segments extend from the disordered state of free curling to the orientation direction, further reducing the structure of molecular entanglement and achieving the tearability of the pipe. The change in the ordered state of orientation significantly improves the strength of the copolymer along the longitudinal direction of the pipe, while the strength perpendicular to the pipe direction decreases, further enhancing the strength and tearability of the pipe. The pipe with tearability is made into a heat-shrinkable tube through irradiation and expansion processes, and the resulting heat-shrinkable tube has the same tearability as before expansion. In the present invention, ethylene-acrylate copolymer is used as the matrix resin, and the degree of orientation of the internal molecular chains of the ethylene-acrylate copolymer is controlled during the extrusion process to ensure that the degree of orientation is in the range of 40%-95%. Further, the extruded pipe is irradiated and crosslinked through an irradiation process to change its ordinary two-dimensional linear molecular structure into a three-dimensional network molecular structure. The three-dimensional network molecular structure not only solidifies 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 oriented three-dimensional network molecules will shrink, thereby changing their degree of orientation. By controlling the appropriate irradiation dose and the crosslinking degree of the ethylene-acrylate copolymer during the irradiation process, it is finally achieved that after the peelable heat-shrinkable tube shrinks by more than 35% at 200°C, the degree of orientation of the molecular chains of the peelable heat-shrinkable tube is 30%-85%, enabling it to have the property of being tearable at room temperature.

[0023] In some embodiments, the extrusion process controls the degree of molecular chain orientation of the extruded pipe to be 50%-90%. After the shrinkage rate of the peelable heat-shrinkable tube is more than 35% when heated at 200°C, the degree of orientation of the molecular chains of the peelable heat-shrinkable tube is 40%-85%. These two ranges of degree of orientation make the linear tear performance of the prepared peelable heat-shrinkable tube more excellent.

[0024] In some embodiments, an irradiation process is further included after the extrusion process. The irradiation dose provided by the irradiation equipment in the irradiation process is 100 - 300 kGy. The degree of orientation of the easily peelable heat shrinkable tube depends not only on the extrusion process but also on the irradiation process. In 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 between 8.5 and 30, extruded tubes with a molecular chain orientation degree of 40% - 95% are 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 degree of crosslinking. Finally, after the easily peelable heat shrinkable tube shrinks by more than 35% at a temperature of 200°C, the molecular chain orientation degree of the easily peelable heat shrinkable tube is 30% - 85%, and it has the property of being tearable at room temperature. Of course, the tearable property of the easily peelable heat shrinkable tube can also be achieved by adding a crosslinking agent to the ethylene-acrylate copolymer and then adjusting the irradiation dose in the irradiation process. The irradiation equipment can be an electron accelerator irradiation device, a radioactive isotope irradiation device, which is not limited here.

[0025] When the content of acrylate monomers in the ethylene-acrylate copolymer increases, it causes a further decrease in the orderliness of its molecular chain, and at the same time increases the content of acrylic acid side groups, resulting in a decrease in its crystallinity and a decrease in the melting point. The tearability will become better. 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 tube becoming low will occur, affecting the forming and use of the tube. Therefore, the acrylic acid content is preferably 9wt% - 30wt%.

[0026] 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 indicates that the average molecular weight of the resin is small, the viscosity is low, the fluidity is good, and it is easy to process and form, but the mechanical properties are poor; a low melt index indicates that the average molecular weight of the resin is large, the viscosity is large, the fluidity is poor, and the forming and processing are more difficult, but the mechanical properties are good. In some embodiments, the melt index (MI) of the ethylene-acrylate copolymer is (0.5 - 6) g / 10 min. The melt index within this range can meet better fluidity and better mechanical properties.

[0027] In some embodiments, the tear strength of the ethylene-acrylate copolymer is less than 75 kN / m. The tear strength within this range is convenient for better tearing off the heat shrinkable tube.

[0028] In some embodiments, the tensile strength of the ethylene-acrylate copolymer is 15 - 24 Mpa. The tensile strength within this range can improve the tensile strength of the heat shrinkable tube.

[0029] To further improve the tensile strength of the easily peelable heat shrinkable tube, we can add polymers such as polyethylene (PE), polyolefin elastomer (POE), ethylene-vinyl acetate copolymer (EVA), etc.

[0030] The polyethylene (PE) can be one of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), and linear low-density polyethylene (LLDPE); the polyolefin elastomer (POE) can be one of the random copolymer elastomers of ethylene with 1-butene, ethylene with 1-hexene, ethylene with 1-octene, etc.; when selecting ethylene-vinyl acetate copolymer (EVA), an EVA with a vinyl acetate (VA) content of less than 20% has a better strengthening effect.

[0031] Of course, to obtain higher-performance pipes, we can also add additives such as antioxidants and lubricants. Antioxidants are beneficial to improving the antioxidant performance and aging resistance of the easily peelable heat shrinkable tube and extending its service life. Antioxidants include at least one of asymmetric hindered phenol antioxidants, aromatic amine antioxidants, thioether antioxidants, and phosphite antioxidants. Lubricants are beneficial to promoting more uniform mixing of various raw materials and include at least one of PTFE powder, zinc stearate, magnesium stearate, silicone, calcium stearate, or ethylene bisstearamide.

[0032] In some embodiments, the ratio representing the tearing linearity is in the range of 50%:50% to 48%:52%. The closer the ratio is to 50%:50%, the better the tearing linearity performance.

[0033] In some embodiments, the inner diameter of the easily peelable heat shrinkable tube is 0.3 - 16 mm;

[0034] In some embodiments, the wall thickness of the easily peelable heat shrinkable tube is 0.1 - 2 mm.

[0035] 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 pipe 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 curing 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 ethylene-acrylate copolymer during the radiation process, after the prepared easily peelable heat shrinkable tube shrinks by more than 35% at a temperature of 200 °C, the molecular chain orientation degree reaches 30%-85%, thus realizing the tearable performance of the heat shrinkable tube. While FEP material is not radiation-resistant, and 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 pipe to 40%-95% through the extrusion process, making a heat shrinkable tube through 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 the ethylene-acrylate copolymer are relatively low compared with those of the fluororesin substrate, which also makes the use shrinkage temperature of the easily peelable heat shrinkable tube of the ethylene-acrylate copolymer lower than that of the fluorine substrate.

[0036] 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.

[0037] In some embodiments, at a temperature of 110 °C, the shrinkage ratio of the easily peelable heat shrinkable tube is 1.3 - 4.5.

[0038] Thus, 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 large-ratio non-shrinkable polymer pipes.

[0039] The technical solutions 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.

[0040] Measurement of orientation degree

[0041] 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: a pipe with an extruded inner diameter of d1 (mm) and a wall thickness of w (mm) (depending on the dimensions of the extruded pipe, the corresponding model 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 draw ratio calculation formula is as follows:

[0042]

[0043] The orientation degree of the molecular chain of the extruded pipe was studied by X-ray diffraction (D / Max-rA type rotating anode X-ray diffractometer), and the orientation degree of the molecular chain after the heat shrinkable tube was completely shrunk. The orientation degree was calculated using the following formula:

[0044]

[0045] П is the orientation degree, and H is the angle of the equatorial diffraction along the Debye ring for one diffraction radian distribution. During measurement, the half-width of the intensity distribution, that is, half of the maximum intensity on the arc segment, was used as the starting point and the ending point of the arc segment.

[0046] Test of tearing linearity

[0047] In order to more clearly judge the tearing linearity, the following method was used for measurement. A cut with a length of 40 mm was set at one end of a specimen with a length of 1000 mm. The cut was set parallel to the tube length direction at the center of the tube using a fixture. The tube was torn from the cut part to the other end at a speed of 200 mm / min. The weights of the two heat shrinkable tubes torn were measured respectively, and the weight ratio was calculated. It can be judged that the closer the ratio is to 50%:50%, the higher the tearing linearity.

[0048] Tearing strength test

[0049] After a 40 mm cut was formed by cutting with a tool, a 100 mm sample was taken and torn through a tensile testing machine at a speed of 200 mm / min, and the maximum force at that time was measured as the tearing strength. The same composition samples were measured 3 times, and their weighted average value was calculated.

[0050] Determination of the complete shrinkage temperature

[0051] A 100 mm sample was taken, and the sample was heated using a programmed temperature oven. With 50 °C as the starting shrinkage temperature, the temperature of the oven was increased by 10 °C every 3 min, so that the sample shrank for 3 min at each temperature, and the shrinkage temperature was recorded until it was continuously measured 3 times and the inner diameter after shrinkage did not change. Then the temperature recorded for the first time in the continuous 3 times was the complete shrinkage temperature.

[0052] Determination of the shrinkage rate

[0053] A 100 mm sample was taken and shrunk for 3 min under the temperature condition of 200 °C. The inner diameters of the sample before and after shrinkage were measured. It was calculated according to the following formula: Shrinkage rate = (Inner diameter before shrinkage - Inner diameter after shrinkage) / Inner diameter before shrinkage × 100%

[0054] Example 1

[0055] Masterbatch processing

[0056] Add ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 0.1 to a high-speed mixer and stir for 3 - 5 minutes. Feed the material obtained from the above process 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 pellets.

[0057] Extrude pipes

[0058] Use the above-obtained masterbatch pellets to form pipes with a single-screw extruder. A full-thread screw is used, and at a screw speed of 5 - 45 rpm and a die temperature of 130 - 190 °C, control the molecular chain orientation degree of the extruded pipes at 50% and carry out extrusion molding. 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 is obtained.

[0059] Irradiation crosslinking

[0060] Irradiate the above semi-finished sleeve with an electron accelerator device at an irradiation dose of 200 KGy for irradiation crosslinking.

[0061] Expand pipes

[0062] Expand the above irradiated crosslinked pipes 2 times at 130 - 260 °C with an expansion device; then cool and shape 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, with a full shrinkage temperature of 110 °C, a shrinkage rate of 50%, and a molecular chain orientation degree of 45% after full shrinkage.

[0063] Example 2

[0064] Masterbatch processing

[0065] Except for replacing ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) with ethylene-ethyl acrylate copolymer (EEA, ELVALOY TM AC 2116), the manufacturing was carried out in the same manner as in Example 1.

[0066] Extrude pipes

[0067] Semi-form in the same manner as in Example 1.

[0068] Irradiation crosslinking

[0069] Irradiate in the same manner as in Example 1.

[0070] Expand pipes

[0071] 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 full shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after full shrinkage was 44%.

[0072] Example 3

[0073] Masterbatch processing

[0074] Manufacture was carried out in the same manner as in Example 1, except that ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) was replaced with ethylene-butyl acrylate copolymer (EBA, AC 3717).

[0075] Extrusion of the tube

[0076] Semi-forming was carried out in the same manner as in Example 1.

[0077] Irradiation crosslinking

[0078] Irradiation was carried out in the same manner as in Example 1.

[0079] Expansion of the tube

[0080] 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 full shrinkage temperature was 110 °C, the shrinkage rate was 50%, and the degree of molecular chain orientation after full shrinkage was 46%.

[0081] Example 4

[0082] Masterbatch processing

[0083] Manufacture was carried out in the same manner as in Example 1, except that ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) was replaced with ethylene-methyl methacrylate copolymer (EMMA, Sumitomo CM8014).

[0084] Extrusion of the tube

[0085] Semi-forming was carried out in the same manner as in Example 1.

[0086] Irradiation crosslinking

[0087] Irradiation was carried out in the same manner as in Example 1.

[0088] Expansion of the tube

[0089] 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 degree of molecular chain orientation after complete shrinkage was 45%.

[0090] Example 5

[0091] Masterbatch processing

[0092] Manufacture was carried out in the same manner as in Example 1.

[0093] Extruded pipe

[0094] Semi-forming was carried out in the same manner as in Example 1, except that the degree of molecular chain orientation of the extruded pipe in the extrusion process was controlled at 40%.

[0095] Irradiation crosslinking

[0096] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled at 180 kGy.

[0097] Expansion of the pipe

[0098] 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 degree of molecular chain orientation after complete shrinkage was 35%.

[0099] Example 6

[0100] Masterbatch processing

[0101] Manufacture was carried out in the same manner as in Example 1.

[0102] Extruded pipe

[0103] Semi-forming was carried out in the same manner as in Example 1, except that the degree of molecular chain orientation of the extruded pipe was controlled at 70%.

[0104] Irradiation crosslinking

[0105] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled at 150 kGy.

[0106] Expansion of the pipe

[0107] 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 degree of molecular chain orientation after complete shrinkage was 60%.

[0108] Example 7

[0109] Masterbatch processing

[0110] Manufacture was carried out in the same manner as in Example 1.

[0111] Extruded pipe

[0112] Semi-forming was carried out in the same manner as in Example 1, except that the molecular chain orientation degree of the extruded pipe was controlled at 90%.

[0113] Irradiation crosslinking

[0114] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled at 160 KGy.

[0115] Expanded pipe

[0116] 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 80%.

[0117] Example 8

[0118] Masterbatch processing

[0119] Manufacture was carried out in the same manner as in Example 1.

[0120] Extruded pipe

[0121] Semi-forming was carried out in the same manner as in Example 1, except that the molecular chain orientation degree of the extruded pipe was controlled at 95%.

[0122] Irradiation crosslinking

[0123] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled at 180 KGy.

[0124] Expanded pipe

[0125] 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 85%.

[0126] Example 9

[0127] Masterbatch processing

[0128] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 0.1 was changed to ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TMExcept that the mass ratio of antioxidant (antioxidant 1218) / antioxidant (antioxidant 1010) / sensitizing crosslinking agent (FRD-301) was 60 / 0.1 / 0.1, it was manufactured in the same manner as in Example 1.

[0129] Extruded pipe

[0130] Semi-forming was carried out in the same manner as in Example 1.

[0131] Irradiation crosslinking

[0132] Except that the irradiation dose was controlled at 100 KGy, irradiation was carried out in the same manner as in Example 1.

[0133] Expanded pipe

[0134] 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 46%.

[0135] Example 10

[0136] Masterbatch processing

[0137] It was manufactured in the same manner as in Example 1.

[0138] Extruded pipe

[0139] Semi-forming was carried out in the same manner as in Example 1.

[0140] Irradiation crosslinking

[0141] Except that the irradiation dose was controlled at 100 KGy, irradiation was carried out in the same manner as in Example 1.

[0142] Expanded pipe

[0143] 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 42%.

[0144] Example 11

[0145] Masterbatch processing

[0146] It was manufactured in the same manner as in Example 1.

[0147] Extruded pipe

[0148] Semi-forming was carried out in the same manner as in Example 1.

[0149] Irradiation crosslinking

[0150] The above semi-finished casing was irradiated with a cobalt-60 (Co) controlled irradiation dose of 300 kGy and irradiated in the same manner as in Example 1.

[0151] Expanded tubing

[0152] 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 47%.

[0153] Example 12

[0154] Masterbatch processing

[0155] Manufacture was carried out in the same manner as in Example 1.

[0156] Extruded tubing

[0157] Semi-forming was carried out in the same manner as in Example 1.

[0158] Irradiation crosslinking

[0159] Irradiation was carried out in the same manner as in Example 1.

[0160] Expanded tubing

[0161] 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 degree of molecular chain orientation after complete shrinkage was 45%.

[0162] Example 13

[0163] Masterbatch processing

[0164] Manufacture was carried out in the same manner as in Example 1.

[0165] Extruded tubing

[0166] Semi-forming was carried out in the same manner as in Example 1.

[0167] Irradiation crosslinking

[0168] Irradiation was carried out in the same manner as in Example 1.

[0169] Expanded tubing

[0170] 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 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 degree of molecular chain orientation after complete shrinkage was 45%.

[0171] Comparative Example 1

[0172] Masterbatch processing

[0173] Low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 0.1 were added to a high-speed mixer and stirred for 3 - 5 minutes. The material obtained from the above process was fed into a twin-screw extruder with a barrel diameter of 30 mm, and extruded at a screw speed of 45 rpm and a die temperature of 130 - 200 °C, then strand pelletized and water-cooled to finally form masterbatch pellets.

[0174] Extruding pipes

[0175] The masterbatch pellets obtained above were used to form pipes by means of a single-screw extruder. A full-thread screw was used, and at a screw 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 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 was obtained.

[0176] Irradiation crosslinking

[0177] The above semi-finished sleeve was irradiated using an electron accelerator device with an irradiation dose of 200 kGy for irradiation crosslinking.

[0178] Expanding pipes

[0179] The above irradiated crosslinked pipe was filled with nitrogen in an expansion device at 130 - 260 °C to expand the pipe; then it was cooled and shaped 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, a complete shrinkage temperature of 120 °C, a shrinkage rate of 50%, and a molecular chain orientation degree of 43% after complete shrinkage.

[0180] Comparative Example 2

[0181] Masterbatch processing

[0182] Except that low-density polyethylene (LDPE) was replaced with ethylene-vinyl acetate copolymer (EVA, 7350M), it was manufactured in the same manner as Comparative Example 1.

[0183] Extruding pipes

[0184] Semi-forming was carried out in the same manner as Comparative Example 1.

[0185] Irradiation crosslinking

[0186] Except that the irradiation dose was controlled at 200 kGy, irradiation was carried out in the same manner as Comparative Example 1.

[0187] Expanded pipe

[0188] The expansion molding was carried out in the same manner as in 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 molecular chain orientation degree after complete shrinkage was 45%.

[0189] Comparative Example 3

[0190] Masterbatch processing

[0191] Except for replacing low-density polyethylene (LDPE) with polyolefin elastomer (POE, ENGAGE TM 8180), the manufacturing was carried out in the same manner as in Comparative Example 1.

[0192] Extruded pipe

[0193] The semi-forming was carried out in the same manner as in Comparative Example 1.

[0194] Irradiation crosslinking

[0195] Except for controlling the irradiation dose to 200 KGy, the irradiation was carried out in the same manner as in Comparative Example 1.

[0196] Expanded pipe

[0197] The expansion molding was carried out in the same manner as in 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 molecular chain orientation degree after complete shrinkage was 42%.

[0198] Comparative Example 4

[0199] Masterbatch processing

[0200] The manufacturing was carried out in the same manner as in Example 1.

[0201] Extruded pipe

[0202] Except for controlling the molecular chain orientation degree of the extruded pipe at 15%, the semi-forming was carried out in the same manner as in Example 1.

[0203] Irradiation crosslinking

[0204] The irradiation was carried out in the same manner as in Example 1.

[0205] Expanded pipe

[0206] 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 13%.

[0207] Comparative Example 5

[0208] Masterbatch processing

[0209] Manufacture was carried out in the same manner as in Example 1.

[0210] Extruded pipe

[0211] Semi-forming was carried out in the same manner as in Comparative Example 1..

[0212] Irradiation crosslinking

[0213] Irradiation was carried out in the same manner as in Example 1, except that the irradiation dose was controlled to 50 KGy.

[0214] Expanded pipe

[0215] 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 16%.

[0216] Comparative Example 6

[0217] 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.

[0218] For the heat shrinkable tubes prepared above, the preparation condition parameters of Examples 1-13 are shown in Table 1, and the preparation condition parameters of Comparative Examples 1-6 are shown in Table 2. According to the above-mentioned method for measuring the orientation degree, the molecular chain orientation degree of the extruded pipe during the extrusion process was controlled, and the molecular chain orientation degree of the obtained heat shrinkable tube after complete shrinkage was measured; according to the above-mentioned test method for tear linearity, the tear linearity was measured; according to the above-mentioned test method for tear strength, the tear strength was measured; according to the above-mentioned method for measuring the complete shrinkage temperature, the complete shrinkage temperature was measured; according to the above-mentioned method for measuring the shrinkage rate, the shrinkage rate was measured. The measurement results of Examples 1-13 and Comparative Examples 1-6 are shown in Table 3.

[0219] Table 1 Preparation condition parameters of Examples 1 to 13

[0220]

[0221] Table 2 Preparation condition parameters of Comparative Examples 1 to 6

[0222]

[0223] Table 3 Measurement results of Examples 1-13 and Comparative Examples 1-6

[0224]

[0225] From Examples 1-4 and Comparative Examples 1-3, it can be seen 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. From Examples 1, 5-8 and Comparative Example 4, it can be seen that in addition to the type of polymer, it is also necessary to control the molecular chain orientation degree of the extruded tube in the extrusion process to be 40%-95%. At the same time, from Examples 9-11 and Comparative Example 5, it can be seen that it is necessary to control the irradiation dose to obtain a suitable crosslinking degree, and finally make the molecular chain orientation degree of the prepared easily peelable heat-shrinkable tube be 30%-85%, having a straight-line tear property. From Examples 1-13 and Comparative Example 6, it can be seen that compared with the FEP heat-shrinkable tube, the easily peelable heat-shrinkable tube provided by the present invention has a lower shrinkage temperature and a higher shrinkage rate, and is suitable for assisting the shrinkage of high-molecular non-shrinkable tubes with a large magnification.

[0226] 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 to other related technical fields, shall be equally included in the patent protection scope of the present invention.

Claims

1. An easily peelable heat shrinkable tube having linear tearability in the longitudinal direction of the tube, characterized in that, The preparation materials of the easily peelable heat shrinkable tube include an ethylene-acrylate copolymer as the matrix resin. In the extrusion process, the molecular chain orientation degree of the extruded tube is controlled to be 40%-95%. The shrinkage rate of the easily peelable heat shrinkable tube when heated at 200°C is more than 35%. After shrinking by more than 35% at 200°C, the molecular chain orientation degree of the easily peelable heat shrinkable tube is 30%-85%.

2. The easily peelable heat shrinkable tube according to claim 1, wherein In the extrusion process, the molecular chain orientation degree of the extruded tube is controlled to be 50%-90%. The shrinkage rate of the easily peelable heat shrinkable tube when heated at 200°C is more than 35%. After shrinking by more than 35% at 200°C, the molecular chain orientation degree of the easily peelable heat shrinkable tube is 40%-85%.

3. The peelable heat shrinkable tube according to claim 1, wherein, After the extrusion process, an irradiation process is further included. The irradiation dose provided by the irradiation equipment in the irradiation process is 100-300 KGy.

4. 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).

5. The peelable heat shrinkable tube according to claim 1, characterized in that, The melt index of the ethylene-acrylate copolymer is (0.5-10) g / 10 min, and the acrylic acid content is 9 wt%-30 wt%.

6. The easily peelable heat shrinkable tube according to claim 1, characterized in that, The tear strength of the ethylene-acrylate copolymer is lower than 75 kN / m.

7. The peelable heat-shrinkable tube according to claim 1, characterized in that, The tensile strength of the ethylene-acrylate copolymer is 15-24 Mpa.

8. The peelable heat-shrinkable tube according to claim 1, wherein The ratio representing the tear linearity is in the range of 50%:50% to 48%:52%.

9. The peelable heat shrinkable tube according to claim 1, wherein The inner diameter of the easily peelable heat shrinkable tube is 0.3-16 mm.

10. The easily peelable heat shrinkable tube according to claim 1, wherein, The wall thickness of the easily peelable heat shrinkable tube is 0.1-2 mm.

Images