Easily stripped pipe

Abstract

The invention discloses an easy-to-peel pipe which adopts an ethylene-acrylate copolymer as matrix resin, as 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 the molecules is reduced; the ethylene-acrylate copolymer has the advantages that the degree of orientation of the molecular chain in the ethylene-acrylate copolymer is further controlled through the extrusion process, the degree of orientation is guaranteed to be within the range of 23%-95%, the molecular chain and the chain segment of the ethylene-acrylate copolymer extend from a freely curled disordered state to the orientation direction, and the cohesive strength of the molecular chain of the ethylene-acrylate copolymer is reduced; the entangled structure of molecules is further reduced, and the tearability of the pipe is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of pipe materials, and particularly relates to an easily peelable pipe. Background Art

[0002] The easily peelable pipe can be used as a protective pipe for precision instruments, electronic components, etc., a liquid guide hose, an assembly jig for a medical device introduction pipe for introducing a guide wire into the body, a liquid guide hose, etc. When not needed, the pipe is removed by peeling.

[0003] At present, the material of the easily peelable pipe on the market is mainly PTFE. Its product price is expensive, and it is mainly manufactured and produced abroad. The production process is difficult and the technical threshold is high. With the rapid development of medicine, the demand for easily peelable pipes is increasing. However, the long procurement cycle abroad has greatly affected the development of domestic medicine. Our company has independently developed an easily peelable pipe made of polyolefin and its copolymer resin. Its tear strength is lower than that of the PTFE easily peelable pipe, and there is no adhesion to the internal material, which can completely replace the PTFE easily peelable pipe and provides a new choice for easily peelable pipes. Summary of the Invention

[0004] The main purpose of the present invention is to provide an easily peelable pipe made of polyolefin and its copolymer resin, whose tear strength is lower than that of the PTFE tearable pipe, and there is no adhesion to the internal material.

[0005] To achieve the above purpose, the present invention provides an easily peelable pipe, which has linear tearability in the length direction of the pipe. The preparation material of the easily peelable pipe contains ethylene-acrylate copolymer as the matrix resin, and the extrusion process controls the molecular chain orientation degree of the extruded pipe to be 23%-95%.

[0006] In some embodiments of the present application, the molecular chain orientation degree of the extruded pipe is 30%-90%.

[0007] 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).

[0008] 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%.

[0009] In some embodiments of the present application, the tear strength of the ethylene-acrylate copolymer is lower than 75 kN / m.

[0010] In some embodiments of the present application, the tensile strength of the ethylene-acrylate copolymer is 15-24 Mpa.

[0011] In some embodiments of the present application, the ratio representing the tear linearity is in the range of 50%:50% to 48%:52%.

[0012] In some embodiments of the present application, the inner diameter of the easily peelable pipe is 0.3-16 mm.

[0013] In some embodiments of the present application, the wall thickness of the easily peelable pipe is 0.1-2 mm.

[0014] Advantageous effects achievable by the present invention:

[0015] For the easily peelable pipe 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, the orientation degree of the internal molecular chains of the ethylene-acrylate copolymer is controlled through the extrusion process to ensure that the orientation degree is in the range of 23%-95%, causing the ethylene-acrylate copolymer molecular chains and segments to stretch 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. Detailed implementation manners

[0016] 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.

[0017] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0018] 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 indicating the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the technical solutions between various embodiments may be combined with each other, but it must be based on the fact that those of ordinary skill in the art can implement them. 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.

[0019] The polymer orientation structure refers to a structure in which molecular chains or other structural units are preferentially aligned along the direction of an external force and frozen under the action of a certain external force. The ethylene-acrylate copolymer obtained by melt extrusion undergoes an extrusion and stretching process, and the molecular chains of the ethylene-acrylate copolymer are aligned along the stretching direction, that is, preferentially oriented along the stretching direction.

[0020] The ethylene-acrylate copolymer is formed by copolymerizing ethylene with acrylate, and mainly includes 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.

[0021] High-molecular materials exist in a state where the molecular chains that make them up are entangled like wool balls. In the molded body formed using high-molecular materials, the state of molecular entanglement is also maintained, and the physical properties of the molded body are greatly affected by the structure of molecular entanglement. During the research on peelable pipes, we unexpectedly found that when the ethylene-acrylate copolymer is used as the matrix resin and the degree of orientation of the molecular chains of the extruded pipe in the extrusion process is ensured to be in the range of 23%-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 the 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, resulting in 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 in the extrusion process and ensuring that the degree of orientation is in the range of 23%-95%, the ethylene-acrylate copolymer molecular chains and segments are extended from the disordered state of free curling to the orientation direction, further reducing the structure of molecular entanglement, realizing the tearability of the pipe. The change in the ordered state of orientation significantly improves the strength of the copolymer along the length direction of the pipe, while the strength in the direction perpendicular to the pipe decreases, further enhancing the strength and tearability of the pipe.

[0022] In the extrusion process, generally by controlling the traction speed and extrusion speed of the extruded pipe, extruded pipes with different draw ratios are obtained. By controlling the draw ratio of the extruded pipe to be between 7 and 30, extruded pipes with a molecular chain orientation degree of 23%-95% are obtained.

[0023] When the content of acrylate monomers in ethylene-acrylate copolymer increases, the orderliness of its molecular chain 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 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 is preferably 9wt%-30wt%.

[0024] The melt index (MI) is an index indicating 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 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 means that the average molecular weight of the resin is large, the viscosity is large, the fluidity is poor, and the forming process is a bit 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, and the melt index within this range can meet better fluidity and better mechanical properties.

[0025] 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.

[0026] In some embodiments, the tensile strength of the ethylene-acrylate copolymer is 15-24 Mpa, and the tensile strength within this range can improve the tensile strength of the pipe.

[0027] In order to further improve the tensile strength of the easily peelable pipe, we can add polymers such as polyethylene (PE), polyolefin elastomer (POE), ethylene-vinyl acetate copolymer (EVA), etc.

[0028] The polyethylene (PE) can be one of high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE); the polyolefin elastomer (POE) can be one of random copolymer elastomers such as ethylene and 1-butene, ethylene and 1-hexene, ethylene and 1-octene, etc.; when selecting ethylene-vinyl acetate copolymer (EVA), an enhanced effect is better when the content of vinyl acetate (VA) is less than 20%.

[0029] Of course, in order to obtain pipes with higher performance, 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 pipes, and prolonging the service life of the easily peelable pipes. The 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 among various raw materials, and include at least one of PTFE powder, zinc stearate, magnesium stearate, silicone, calcium stearate, or ethylene bisstearamide.

[0030] 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.

[0031] Measurement of orientation degree

[0032] A single-screw extruder was used, and the specifications of its extrusion die were as follows: the die orifice was D1 (mm), the mandrel was D2 (mm), and the dimensions of the extruded pipe were as follows: the inner diameter of the extrusion was d1 (mm), and the wall thickness was w (mm) (depending on the different 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, extruded pipes with different draw ratios were obtained. The formula for calculating the draw ratio is as follows:

[0033]

[0034] 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 was calculated using the following formula:

[0035]

[0036] П is the orientation degree, and H is the angle of the equatorial diffraction along one diffraction arc of the Debye ring. 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 ending point of the arc segment.

[0037] Test of tear linearity

[0038] In order 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 specimen with a length of 1000 mm. The cut was set parallel to the center of the pipe and the pipe length direction using a fixture. The pipe was torn from the cut part to the other end of the pipe 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.

[0039] Tear strength test

[0040] After cutting a 40-mm incision with a cutter, a 100-mm sample was taken and torn at a speed of 200 mm / min using a tensile testing machine. The maximum force at that time was measured as the tear strength. The same composition of samples was measured three times, and the weighted average was calculated.

[0041] Example 1

[0042] Masterbatch processing

[0043] Ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) / 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 diameter of 30 mm and extruded at a screw speed of 45 rpm and a temperature of 130 - 200 °C, followed by strand pelletization and water cooling to finally form masterbatch pellets.

[0044] Extruding pipes

[0045] The masterbatch pellets obtained above were used to form pipes with a single-screw extruder. A full-thread screw was used, and the screw speed was 5 - 45 rpm, and the die temperature was 130 - 190 °C. The molecular chain orientation degree of the extruded pipe was controlled at 50%, and the 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.

[0046] Example 2

[0047] Masterbatch processing

[0048] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) was replaced with ethylene-ethyl acrylate copolymer (EEA, ELVALOY TM AC 2116), the manufacturing was carried out in the same manner as in Example 1.

[0049] Extruding pipes

[0050] The molding was carried out in the same manner as in Example 1.

[0051] Example 3

[0052] Masterbatch processing

[0053] Except that the ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) was replaced with ethylene-butyl acrylate copolymer (EBA, AC 3717), the manufacturing was carried out in the same manner as in Example 1.

[0054] Extruding pipes

[0055] Molding was carried out in the same manner as in Example 1.

[0056] Example 4

[0057] Masterbatch processing

[0058] Except that ethylene-methyl acrylate copolymer (EMA, DuPont ELVALOY TM AC 1218) was replaced with ethylene-methyl methacrylate copolymer (EMMA, Sumitomo CM8014), manufacturing was carried out in the same manner as in Example 1.

[0059] Extrusion of pipes

[0060] Molding was carried out in the same manner as in Example 1.

[0061] Example 5

[0062] Masterbatch processing

[0063] Manufacturing was carried out in the same manner as in Example 1.

[0064] Extrusion of pipes

[0065] Except that the degree of orientation was controlled at 23%, molding was carried out in the same manner as in Example 1.

[0066] Example 6

[0067] Masterbatch processing

[0068] Manufacturing was carried out in the same manner as in Example 1.

[0069] Extrusion of pipes

[0070] Except that the degree of orientation was controlled at 30%, molding was carried out in the same manner as in Example 1.

[0071] Example 7

[0072] Masterbatch processing

[0073] Manufacturing was carried out in the same manner as in Example 1.

[0074] Extrusion of pipes

[0075] Except that the degree of orientation was controlled at 90%, molding was carried out in the same manner as in Example 1.

[0076] Example 8

[0077] Masterbatch processing

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

[0079] Extrusion of pipes

[0080] Molding was carried out in the same manner as in Example 1, except that the degree of orientation was controlled at 95%.

[0081] Comparative Example 1

[0082] Masterbatch processing

[0083] Low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) / antioxidant (antioxidant 1010) (mass ratio) = 60 / 0.1 were added together 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 extrusion was carried out at a screw speed of 45 rpm and a die temperature of 130 - 200 °C, followed by strand drawing, water cooling and pelletizing to finally form masterbatch pellets.

[0084] Extruding pipes

[0085] The masterbatch pellets obtained above were used to carry out pipe forming 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 degree of molecular chain orientation 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.

[0086] Comparative Example 2

[0087] Masterbatch processing

[0088] Manufacture was carried out in the same manner as in Comparative Example 1, except that low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) was replaced with ethylene-vinyl acetate copolymer (EVA, 7350M).

[0089] Extruding pipes

[0090] Molding was carried out in the same manner as in Comparative Example 1.

[0091] Comparative Example 3

[0092] Masterbatch processing

[0093] Manufacture was carried out in the same manner as in Comparative Example 1, except that low-density polyethylene (LDPE, lyondellbasell Lupolen 2426K) was replaced with polyolefin elastomer (POE, ENGAGE TM 8180).

[0094] Extruding pipes

[0095] Molding was carried out in the same manner as in Comparative Example 1.

[0096] Comparative Example 4

[0097] Masterbatch processing

[0098] Manufacture was carried out in the same manner as in Example 1.

[0099] Extruded pipe

[0100] Molding was carried out in the same manner as in Example 1, except that the degree of orientation was controlled at 15%.

[0101] Comparative Example 5

[0102] A commercially available PTFE tearable sheath tube with a specification of AWG 24F was used.

[0103] For the easily peelable tube prepared above, the degree of orientation of the molecular chains of the extruded pipe during the extrusion process was controlled according to the above-mentioned method for measuring the degree of orientation; the tear linearity was measured according to the above-mentioned test method for tear linearity; the tear strength was measured according to the above-mentioned test method for tear strength. The results of Examples 1-8 are shown in Table 1, and the results of Comparative Examples 1-5 are shown in Table 2.

[0104] Table 1 Examples 1 to 8

[0105]

[0106] Table 2 Comparative Examples 1 to 5

[0107]

[0108] It can be seen from Examples 1-4 and Comparative Examples 1-3 that the easily peelable pipe made of polyolefin and its copolymer resin has a great relationship with the type of polymer, and only a specific ethylene-acrylate copolymer can be used to prepare the easily peelable pipe. It can be seen from Examples 1, 5-8 and Comparative Example 4 that in addition to the type of polymer, the degree of orientation of the molecular chains of the extruded pipe in the extrusion process needs to be controlled at 23%-95% so that the prepared pipe has linear tearability. It can be seen from Examples 1-8 and Comparative Example 5 that the tear strength of the easily peelable pipe of the present invention is lower than that of the PTFE easily peelable pipe, and it can replace the PTFE tearable pipe.

[0109] 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 similarly included in the patent protection scope of the present invention.

Claims

1. An easily peelable pipe having linear tearability in the longitudinal direction of the pipe, characterized in that, The material for preparing the easily peelable pipe comprises an ethylene-acrylate copolymer as the matrix resin, and the extrusion process controls the molecular chain orientation degree of the extruded pipe to be 23%-95%.

2. The peelable pipe according to claim 1, wherein The molecular chain orientation degree of the extruded pipe is 30%-90%.

3. The peelable pipe according to claim 1, characterized in that, 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).

4. The peelable pipe according to claim 1, wherein The ethylene-acrylate copolymer has a melt index of (0.5-10) g / 10min and an acrylic acid content of 9wt%-30wt%.

5. The peelable pipe according to claim 1, characterized in that, The tear strength of the ethylene-acrylate copolymer is less than 75 kN / m.

6. The peelable pipe according to claim 1, wherein The tensile strength of the ethylene-acrylate copolymer is 15-24 Mpa.

7. The peelable pipe according to claim 1, wherein The ratio representing the tear linearity is in the range of 50%:50% to 48%:52%.

8. The easily peelable pipe according to claim 1, wherein The inner diameter of the easily peelable pipe is 0.3-16 mm.

9. The peelable pipe according to claim 1, wherein The wall thickness of the easily peelable pipe is 0.1-2 mm.

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