A low-precipitation radiation-resistant medical polypropylene and its preparation method

Abstract

A low-precipitation and radiation-resistant medical polypropylene and its preparation method, characterized in that, by mass, the raw material composition includes: polypropylene resin: 80-99 parts, peroxide masterbatch: 1-10 parts, radiation-stable masterbatch: 1-10 parts, nucleating agent: 0.05-1 part, acid absorbent: 0.05-0.5 part. The present invention provides a low-precipitation and radiation-resistant medical polypropylene and its preparation method. Through the twin-screw extrusion method, the peroxide masterbatch is first added for a controlled rheology reaction to increase the melt index and reduce the polypropylene molecular weight distribution index, thereby improving the mechanical properties of the polypropylene. At the same time, the regular polymer chain structure promotes more crystallization, which is beneficial to improving the radiation resistance of the polymer. Because the antioxidant contained in the radiation-stable masterbatch easily captures free radicals and affects the effectiveness of the controlled rheology reaction, the radiation-stable masterbatch is added after the controlled rheology reaction initiated by the peroxide is basically completed, maximizing the retention of the radiation stabilizer content in the material to improve the radiation resistance. In addition, by injecting supercritical carbon dioxide fluid, its strong dissolution and extraction ability can elute the small molecule resin contained in the material, and then vacuum devolatilization is carried out to reduce the content of easily precipitable substances in the material and improve the purity of the material.

Description

Technical Field

[0001] The present invention belongs to the field of processing of polymer composites, and particularly relates to a low-precipitation and radiation-resistant medical polypropylene and a preparation method thereof. Background Art

[0002] At present, the most common sterilization methods for medical polymer materials are means such as high-temperature and high-pressure steam, ethylene oxide fumigation, and radiation sterilization. Since the high-temperature and high-pressure method has incomplete sterilization and is not applicable to those heat-sensitive polymer materials, and the ethylene oxide sterilization method requires long-term analysis and may have chemical residues; therefore, the current sterilization method for medical materials is increasingly tending to use radiation technology for sterilization. The radiation sterilization method directly irradiates medical products with high-energy rays (gamma rays or electron beams) to eliminate microorganisms, which has the advantages of energy conservation, thorough sterilization, no pollution, fast sterilization speed, and continuous operation. In addition, radiation sterilization and disinfection is a "cold disinfection" method, which can sterilize at room temperature and is particularly suitable for some heat-sensitive materials.

[0003] Polypropylene (PP) has excellent chemical resistance, fatigue resistance, is easy to process, and has high transparency and good barrier properties, and is widely used in the medical field. However, when irradiating and sterilizing polypropylene medical products, the problem of radiation resistance of polypropylene materials needs to be solved. This is mainly because polypropylene is prone to chain scission reactions under irradiation, resulting in yellowing and fading of the material surface, and more serious degradation will occur after storage for a period of time after irradiation. On the other hand, small molecular weight resins may precipitate in medical transparent PP products during high-temperature transportation, use or sterilization, causing an increase in haze and a significant decrease in transparency. This is also the most prominent point where the performance of domestic medical PP is significantly inferior to that of foreign counterparts. Summary of the Invention

[0004] In view of the deficiencies in this field, the present invention provides a low-precipitation and radiation-resistant medical polypropylene and a preparation method thereof. Through a twin-screw extrusion method, first, a peroxide masterbatch is added for a controlled rheology reaction to increase the melt index and reduce the polypropylene molecular weight distribution index, thereby improving the mechanical properties of polypropylene. At the same time, the regular polymer chain structure promotes the generation of more crystallization, which is beneficial to enhancing the radiation resistance effect of the polymer. Since the antioxidant contained in the radiation stabilization masterbatch easily captures free radicals and affects the effectiveness of the controlled rheology reaction, the radiation stabilization masterbatch is added after the controlled rheology reaction initiated by peroxide is basically completed, maximizing the retention of the radiation stabilizer content in the material to improve the radiation resistance performance. In addition, by injecting supercritical carbon dioxide fluid, its super strong dissolution and extraction ability can elute the small molecular resins contained in the material, and then vacuum devolatilization is carried out to reduce the content of easily precipitated substances in the material and improve the purity of the material.

[0005] A low-precipitation radiation-resistant medical polypropylene and its preparation method, characterized in that, by mass, the raw material composition includes:

[0006] Polypropylene resin: 80 - 99 parts

[0007] Peroxide masterbatch: 1 - 10 parts

[0008] Irradiation-stable masterbatch: 1 - 10 parts

[0009] Nucleating agent: 0.05 - 1 part

[0010] Acid absorbent: 0.05 - 0.5 part

[0011] The polypropylene resin is selected from at least one of medical-grade homopolypropylene PPH and copolymer polypropylene (PPR or PPB), and the melt index (230 °C, 2.16 kg) is in the range of 1 - 20 g / 10 min. Preferably, the melt index is in the range of 2 - 10 g / 10 min.

[0012] The peroxide masterbatch is prepared by using polypropylene as the matrix, adding peroxide and extruding and pelletizing through a twin-screw extruder; wherein polypropylene is 70 - 90 parts, and peroxide is 10 - 30 parts; preferably, polypropylene is 80 - 85 parts, and peroxide is 15 - 20 parts;

[0013] The peroxide is selected from at least one of dicumyl peroxide (DCP), di-tert-butyl peroxide (DTBP), di-tert-amyl peroxide (DTAP), 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane (DBPH), and 3,6,9-triethyl-3,6,9-trimethyl-1,4,7-triperoxynonane (TX301).

[0014] The irradiation-stable masterbatch is prepared by using polypropylene as the matrix, adding an irradiation stabilizer and nano-inorganic powder and extruding and pelletizing through a twin-screw extruder, wherein polypropylene is 80 - 95 parts, the irradiation stabilizer is 3 - 15 parts, and the nano-inorganic powder is 1 - 5 parts; preferably, polypropylene is 90 - 95 parts, the irradiation stabilizer is 3 - 8 parts, and the nano-inorganic powder is 1 - 3 parts;

[0015] The irradiation stabilizer is a preferred and compound combination of a primary antioxidant, a secondary antioxidant, and a light stabilizer. Among them, the primary antioxidant is selected from at least one of 501 and FS042, the secondary antioxidant is selected from at least one of 626, 618, 168, P-EPQ, DLTDP, DSTDP, and SE-10, and the light stabilizer is selected from at least one of 770, 944, 123, 5050, 228, 622, and 202; the compound ratio of the primary antioxidant, the secondary antioxidant, and the light stabilizer is (4 - 6):(2 - 4):(2 - 4); preferably, the compound ratio of the primary antioxidant, the secondary antioxidant, and the light stabilizer is 5:2:3;

[0016] The nano-inorganic powder is selected from at least one of nano-titanium dioxide, nano-zinc oxide, nano-tin dioxide, nano-tungsten trioxide, and nano-cerium dioxide.

[0017] The nucleating agent is selected from at least one of 3988, HPN900ei, NX8000, NA-11, NA-21, NA-71, NU-100, WBG-II, TMB-5, talc powder, and calcium carbonate.

[0018] The acid absorbent is selected from at least one of magnesium-aluminum hydrotalcite and calcium stearate.

[0019] The present invention also provides a preparation method of the above low-bleeding and radiation-resistant medical polypropylene. The aspect ratio of the length to the diameter of the twin-screw extruder used in the preparation is (56-64):1. A main feeding port is provided on the first section of the barrel of the extruder, an auxiliary feeding port is provided on the fifth section of the barrel, an injection port is provided on the eighth section of the barrel, and a vacuum exhaust port is provided on the fourteenth barrel;

[0020] The temperature of the twin-screw extruder is 160-220 °C, and the screw speed is 100-500 r / min. Preferably, the temperature of the extruder is 180-210 °C, and the screw speed is 300-400 r / min.

[0021] The specific steps of the preparation method are as follows:

[0022] 1) Add polypropylene resin and peroxide masterbatch into a high-speed mixer according to the ratio and mix evenly, and then add them into the main feeding port on the first section of the twin-screw extruder. Through the introduction of peroxide, a controlled rheological reaction is carried out on polypropylene to increase the melt index of polypropylene and narrow its molecular weight distribution;

[0023] 2) Add the radiation-stabilized masterbatch, nucleating agent, and acid absorbent into the extruder from the auxiliary feeding port on the fifth section of the barrel, and inject the pre-prepared supercritical carbon dioxide fluid from the injection port on the eighth section of the barrel. Utilize the strong extraction effect of the supercritical fluid to elute the small-molecule resin contained in the polypropylene;

[0024] 3) After the material is devolatilized through the vacuum exhaust port on the fourteenth section of the barrel in the barrel, it is extruded from the die head into a strip, cooled and pelletized to obtain polypropylene pellets.

[0025] Compared with the prior art, the main advantages of the present invention include:

[0026] 1) By adding key additives step by step, the mutual exclusion of the effects between additives is avoided, ensuring that the added additives have the optimal effect or the maximum retention. The radiation-stabilized masterbatch is added after the controlled rheological reaction of peroxide, which not only ensures the effect of the controlled rheological reaction but also increases the retention of the radiation stabilizer in polypropylene.

[0027] 2) Use peroxide for controlled rheology reaction, which is convenient to regulate the melt index of polypropylene resin and meet the specific application requirements in different fields such as injection molding and spinning. At the same time, the controlled rheology reaction makes the molecular weight distribution of polypropylene narrower, improves the chain segment regularity, and thus obtains more crystallization, enhancing the radiation resistance of the material.

[0028] 3) Utilize the strong dissolution and extraction ability of supercritical fluid. Inject supercritical carbon dioxide fluid into the extruder to elute the small molecule resin contained in polypropylene, and then vacuum devolatilization can significantly reduce the content of easily precipitated substances in the material and improve the precipitation resistance of the material. Specific embodiments

[0029] The following combines specific embodiments to further elaborate the present invention. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. The operation methods without specific conditions noted in the following embodiments are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer.

[0030] The raw material compositions of each embodiment are in parts by mass as shown in Table 1, and the preparation method is as follows:

[0031] Add polypropylene resin (medical grade PPR, melt index 2.4 g / 10min) and peroxide masterbatch to the high-speed mixer according to the ratio in Table 1. After mixing evenly, add them into the twin-screw extruder through the main feeding port. Set the extruder temperature to 180 - 210 °C and the screw speed to 400 r / min. Add the radiation stabilization masterbatch, nucleating agent, and acid absorbent into the extruder through the auxiliary feeding port, and inject the pre-prepared supercritical carbon dioxide fluid from the liquid injection port. After the material is devolatilized through the vacuum exhaust port in the barrel, it is extruded into strands from the die head, cooled, and pelletized to obtain polypropylene pellets.

[0032] Inject the above polypropylene pellets into molds to prepare standard mechanical splines and 1-mm samples. Use the high-energy electron beam generated by an electron accelerator to irradiate the polypropylene splines, set the irradiation dose to 25 kGy, and test the relevant properties of the samples before and after irradiation.

[0033] Table 1

[0034] Component Name Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Comparative Example 2 Comparative Example 3 Polypropylene resin PPR 93 90 95 92 89 90 90 90 Peroxide masterbatch 1 — 2 5 — — — 5 5 5 Peroxide masterbatch 2 — — — 3 3 3 — — — Irradiation stabilizing masterbatch 1 — 5 5 2 5 8 5 5 5 Irradiation stabilizing masterbatch 2 — — — — — — — — — Nucleating agent NX8000 0.4 0.4 0.3 0.3 0.3 0.4 0.4 0.4 Acid absorbent Calcium stearate 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

[0035] Peroxide masterbatch 1 contains 85 parts of PPR and 15 parts of DBPH;

[0036] Peroxide masterbatch 2 contains 85 parts of PPR and 15 parts of DCP;

[0037] Radiation stabilization masterbatch 1 contains 92 parts of PPR, 6 parts of radiation stabilizers (FS042 + 626 + 770), and 2 parts of nano-zinc oxide.

[0038] The irradiated stable masterbatch 2 contains 92 parts of PPR, 6 parts of irradiation stabilizers (501 + 162 + 622), and 2 parts of nano tungsten trioxide.

[0039] The formulation composition of Comparative Example 1 is exactly the same as that of Example 2. The preparation method of Comparative Example 1 is the same as that of the example, except that the peroxide masterbatch, irradiated stable masterbatch, nucleating agent, and acid absorbent are all added to the extruder at the main feeding port.

[0040] The formulation composition of Comparative Example 2 is exactly the same as that of Example 2. The preparation method of Comparative Example 2 is the same as that of the example, except that supercritical carbon dioxide fluid is not injected.

[0041] The formulation composition of Comparative Example 3 is exactly the same as that of Example 2. The preparation method of Comparative Example 3 is the same as that of the example, except that the injected fluid medium is water.

[0042] The samples prepared in the above examples and comparative examples were tested, and the test data are listed in Table 2. The melt index of the sample before irradiation was tested according to GB / T 3682.1; the tensile strength before and after irradiation was tested according to GB / T 1040.2, the notched Izod impact strength was tested according to GB / T 1043.2, and the yellowness index was tested according to ASTM D1925. The haze was tested according to ASTM D1003, and the anti-bleeding performance was characterized by the change in haze before and after the sample was treated at high temperature (130 °C, 30 min). The irradiated samples were subjected to a long-term high-temperature durability test at 130 °C, and the time when yellowing and embrittlement started was recorded.

[0043] Table 2

[0044] Test item Unit Example 1 Example 1 Example 2 Example 2 Example 3 Example 3 Example 4 Example 4 Example 5 Example 5 Comparative Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 2 Comparative Example 3 Comparative Example 3 Irradiation dose kGy 0 25 0 25 0 25 0 25 0 25 0 25 0 25 0 25 Melt index g / 10min 9 — 26 — 16 — 15 — 15 — 17 — 29 — 27 — Tensile strength MPa 27 29 33 34 31 33 30 31 29 30 31 31 32 34 33 33 Notched Izod impact strength <![CDATA[kJ / m 2 > 8.4 8.3 7.5 7.1 7.8 7.2 8.0 7.7 7.9 7.7 7.8 7.0 7.3 7.0 7.6 7.1 Yellowness index — 0.89 0.93 0.91 0.92 1.31 1.38 1.45 1.50 1.67 1.71 0.87 0.96 0.98 1.04 0.94 0.98 Haze (initial) % 10.2 10.1 11.1 11.2 16.7 16.9 15.6 15.7 16.1 16.1 10.6 10.9 11.6 11.8 10.8 11.2 Haze (130°C, 30 min) % 14.3 14.9 15.1 15.8 19.6 20.4 17.9 18.6 19.4 19.8 15.4 15.7 38.4 39.5 28.1 29.6 Yellowing embrittlement time at 130°C Day — >60 — >60 — 51 — >60 — >60 — 27 — >60 — >60

[0045] According to the test results in Table 2, it can be seen from Examples 1 to 5 that the mechanical properties such as tensile strength and notched Izod impact of the polypropylene material provided by the present invention do not change significantly after irradiation, and the sample after irradiation basically does not change color, and the increase in yellowness index is less than 0.1, showing excellent radiation resistance. It can be seen from Examples 1 to 2 that the molecular weight of the polypropylene resin can be adjusted according to the content of the peroxide masterbatch added to the main feeding port to obtain the desired melt index for further processing and application of the material. Adding additives such as irradiated stable masterbatch to the auxiliary feeding port can improve and enhance the radiation resistance of polypropylene. For the 130 °C high-temperature aging test of the irradiated sample, it can reach more than 60 days without yellowing and embrittlement, showing long-term stability. In Examples 3 to 5, as the content of the irradiated stable masterbatch increases, the change range of the mechanical properties and yellowness index of the sample before and after irradiation tends to become smaller, and the yellowing and embrittlement time of the sample also extends with the increase in the content of the irradiation stabilizer.

[0046] In Examples 1 to 5, the small-molecule resin in the material was eluted by the process of injecting supercritical carbon dioxide fluid and then vacuum devolatilization. The haze values of the sample wafers before and after high-temperature treatment were tested to characterize the anti-precipitation performance of the material. It can be seen from the results in Table 2 that the haze change of the samples in the examples was small after high-temperature treatment, and the increase was less than 5, showing excellent low-precipitation performance.

[0047] Comparing Comparative Example 1 with Example 2, it can be seen that when all the additives were added from the main feeding port, since the antioxidant contained in the radiation stabilizer would interfere with the free-radical controlled rheological reaction initiated by the peroxide to a certain extent due to its function of capturing and eliminating free radicals, the melt index change rate of the polypropylene resin decreased; at the same time, the consumption of the antioxidant reduced the long-term high-temperature resistance of the sample, and yellowing and embrittlement occurred after 27 days.

[0048] Comparing Comparative Example 2 with Example 2, it can be seen that without injecting supercritical carbon dioxide fluid, it was very difficult for the small-molecule resin contained in the polypropylene to be discharged by simple vacuum pumping, and the haze of the sample increased sharply after high-temperature treatment, with an increase of more than 25.

[0049] Comparing Comparative Example 3 with Example 2, it can be seen that when the injection medium was water, although the small-molecule substances in the polypropylene could be extracted and eluted to a certain extent in the form of water vapor in the screw, the effect of reducing precipitation was limited, and the haze increase after high-temperature treatment was still more than 15.

[0050] The low-precipitation and radiation-resistant medical polypropylene provided by the present invention and its preparation method add a peroxide masterbatch and a radiation-stabilizing masterbatch from the main feeding port and the auxiliary feeding port respectively through a twin-screw extrusion method, which not only ensures the effect of the controlled rheological reaction but also increases the retention amount of the radiation stabilizer in the polypropylene. The controlled rheological reaction can conveniently regulate the melt index of the polypropylene and is beneficial to improving the radiation resistance of the polypropylene. By the process of injecting supercritical carbon dioxide and then vacuum devolatilization, the small-molecule resin contained in the melt can be eluted by using the strong dissolution and extraction ability of the supercritical fluid, reducing the content of the precipitable substances in the material and improving the purity of the material.

[0051] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the appended claims of this application.

Claims

1. A low-precipitation radiation-resistant medical polypropylene, characterized in that, The raw material composition includes, by mass parts: Polypropylene resin: 80 - 99 parts Peroxide masterbatch: 1 - 10 parts Irradiation - stable masterbatch: 1 - 10 parts Nucleating agent: 0.05 - 1 part Acid absorbent: 0.05 - 0.5 part; The peroxide masterbatch is prepared by taking polypropylene as the matrix, adding peroxide and extruding and pelletizing through a twin - screw extruder; wherein polypropylene is 70 - 90 parts and peroxide is 10 - 30 parts; The irradiation - stable masterbatch is prepared by taking polypropylene as the matrix, adding an irradiation stabilizer and nano - inorganic powder and extruding and pelletizing through a twin - screw extruder, wherein polypropylene is 80 - 95 parts, the irradiation stabilizer is 3 - 15 parts, and the nano - inorganic powder is 1 - 5 parts; The twin - screw extruder used for preparing the low - precipitation and radiation - resistant medical polypropylene has a length - to - diameter ratio of (56 - 64):

1. There is a main feeding port on the first section of the screw barrel of the extruder, an auxiliary feeding port on the fifth section of the screw barrel, an injection port on the eighth section of the screw barrel, and a vacuum exhaust port on the fourteenth screw barrel; The temperature of the twin - screw extruder is 180 - 210 °C, and the screw rotation speed is 300 - 400 r / min; The specific steps of the preparation method are as follows: 1) Add the polypropylene resin and peroxide masterbatch into a high - speed mixer according to the ratio, mix evenly, and then add them into the main feeding port on the first section of the twin - screw extruder; 2) Add the irradiation - stable masterbatch, nucleating agent, and acid absorbent into the extruder from the auxiliary feeding port on the fifth section of the screw barrel, and inject the pre - prepared supercritical carbon dioxide fluid from the injection port on the eighth section of the screw barrel; 3) After the material is devolatilized through the vacuum exhaust port on the fourteenth section of the barrel in the machine barrel, it is extruded and drawn into strips from the die head, cooled and pelletized to obtain polypropylene particles.

2. The low-bleed radiation-resistant medical polypropylene according to claim 1, wherein The polypropylene resin is selected from at least one of medical - grade homopolypropylene and copolymer polypropylene, and has a melt index in the range of 1 - 20 g / 10min under the conditions of 230 °C and 2.16 kg.

3. The low-precipitation radiation-resistant medical polypropylene according to claim 1, wherein The peroxide is selected from at least one of dicumyl peroxide (DCP), di - tert - butyl peroxide (DTBP), di - tert - amyl peroxide (DTAP), 2,5 - dimethyl - 2,5 - bis(tert - butylperoxy)hexane (DBPH), 3,6,9 - triethyl - 3,6,9 - trimethyl - 1,4,7 - triperoxynonane; 4. The low-leaching radiation-resistant medical polypropylene according to claim 1, wherein The irradiation stabilizer is a compound combination of a primary antioxidant, a secondary antioxidant, and a light stabilizer; The primary antioxidant is selected from at least one of 501 and FS042; The secondary antioxidant is selected from at least one of 626, 618, 168, P - EPQ, DLTDP, DSTDP, SE - 10; The light stabilizer is selected from at least one of 770, 944, 123, 5050, 228, 622, 202; The compounding ratio of the primary antioxidant, secondary antioxidant, and light stabilizer is (4 - 6):(2 - 4):(2 - 4); The nano - inorganic powder is selected from at least one of nano - titanium dioxide, nano - zinc oxide, nano - tin dioxide, nano - tungsten trioxide, nano - cerium dioxide; 5. The low-bleeding and radiation-resistant medical polypropylene according to claim 1, wherein The nucleating agent is selected from at least one of 3988, HPN900ei, NX8000, NA - 11, NA - 21, NA - 71, NU - 100, WBG - II, TMB - 5, talc powder, calcium carbonate.

6. The low-extraction and radiation-resistant medical polypropylene according to claim 1, wherein The acid absorbent is selected from at least one of magnesium aluminum hydrotalcite and calcium stearate.