A polypropylene composition for irradiation sterilization and its preparation method

Abstract

A polypropylene composition for irradiation sterilization and its preparation method, characterized in that, by mass, the raw material composition includes: polypropylene resin: 80 - 99 parts, radiation-resistant masterbatch: 1 - 20 parts, nucleating agent: 0.05 - 0.5 parts, antioxidant: 0.1 - 1 part, light stabilizer: 0.1 - 1 part, lubricant: 0.1 - 1 part, acid absorbent: 0.05 - 0.5 parts. The polypropylene composition for irradiation sterilization and its preparation method are to add polyvinyl functional group monomers and nano-inorganic powders in the form of a radiation-resistant masterbatch to the formula. The added polyvinyl functional group monomers are easily and uniformly dispersed in the polypropylene. The double bonds contained therein are excited and opened during the irradiation sterilization process, capturing the tertiary carbon free radicals generated by the polypropylene, and balancing the irradiation degradation of the polypropylene matrix through cross-linking and chain extension reactions. In addition, the applicant has found through a large number of experiments that adding certain nano-oxide inorganic powders to the polypropylene formula to cooperate with the polyvinyl functional group monomers can produce an obvious synergistic effect, further reducing the damage of high-energy rays to the polypropylene and being more conducive to improving the radiation resistance of the polypropylene.

Description

Technical Field

[0001] The present invention belongs to the field of processing of polymer composites, and particularly relates to an irradiated sterilization polypropylene composition and a preparation method thereof. Background Art

[0002] Medical polymer materials must also be sterilized before use. The most common sterilization methods include high-temperature and high-pressure steam, ethylene oxide fumigation, irradiation sterilization, etc. 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-time analysis and may have chemical residues, these two sterilization methods have relatively large disadvantages. Currently, the sterilization method of medical materials is increasingly tending to use irradiation technology for sterilization. The irradiation sterilization method is to directly irradiate medical products with high-energy rays (gamma rays or electron beams) to eliminate microorganisms. It has many advantages, such as energy conservation, thorough sterilization, no pollution, fast sterilization speed, continuous operation, and irradiation 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 the hydrogen on the tertiary carbon atom in the polypropylene molecular chain is very active and is prone to generating free radicals under irradiation, resulting in chain scission reactions, causing the surface to turn yellow and fade, degradation occurs and the performance decreases, and more serious degradation will occur after storing for a period of time after irradiation. Therefore, polypropylene for irradiation sterilization requires special formulation design to be used in the production of medical products that can withstand high-energy rays during the sterilization process. The invention patent with application number CN202010237120.9 uses acetone thiosemicarbazide to eliminate the free radicals generated after polypropylene irradiation; a combination of phenolic antioxidants, thioester antioxidants and phosphite antioxidants is used to prevent or slow down the generation of free radicals during the oxidation aging process. The prepared polypropylene resin composition has excellent radiation resistance and can meet the requirements of electron beam sterilization of medical non-woven fabrics. However, in fact, phenolic antioxidants are easily oxidized by free radicals generated during the irradiation process into quinone and methylquinone chromogenic substances, aggravating the discoloration of the material. The invention patents with application numbers CN202110738644.0, CN202011157863.1 and CN201210487486.7 provide corresponding radiation-resistant polypropylene materials and their preparation methods, and phenolic antioxidants are not used in their formulations. However, the above patent methods can only reduce the degree of discoloration after irradiation, and have no obvious improvement effect on the chain scission reaction caused by polypropylene irradiation degradation and the decrease in mechanical properties such as elongation at break and impact strength. The invention patent with application number CN202110023085.5 adds a cross-linked polymer unsaturated polyolefin with a degree of polymerization of 300-800 on the premise of not using phenolic antioxidants. Through free radicals, a free radical cross-linking reaction between polypropylene and unsaturated polyolefin is realized, and the linear chain is converted into a network structure, so that the strength of the irradiated polypropylene non-woven fabric can be maintained. However, the added unsaturated polyolefin has a macromolecular structure, and it is difficult to move and conformational inversion after being incorporated into polypropylene. Irradiation may cause isomerization reactions and reduce the probability of cross-linking reaction with polypropylene. In addition, a relatively large amount of unsaturated polyolefin needs to be added, which is likely to cause a decrease in the mechanical strength of the polypropylene matrix. Summary of the Invention

[0004] In view of the deficiencies in this field, the present invention provides a polypropylene composition for irradiation sterilization and its preparation method, which is in the form of a radiation-resistant masterbatch, and a multi-vinyl functional group monomer and a nano-inorganic powder are added to the formula. The added multi-vinyl functional group monomer is easily and uniformly dispersed in the polypropylene. The double bonds contained therein are excited during the irradiation sterilization process to open the double bonds, capture the tertiary carbon free radicals generated by the polypropylene, and balance the irradiation degradation of the polypropylene matrix through cross-linking and chain extension reactions. In addition, the applicant has found through a large number of experiments that adding certain nano-oxide inorganic powders to the polypropylene formula to cooperate with the multi-vinyl functional group monomer can produce an obvious synergistic effect, further reducing the damage of high-energy rays to the polypropylene and being more conducive to improving the radiation resistance of the polypropylene.

[0005] A polypropylene composition for irradiation sterilization and its preparation method, characterized in that, by mass, the raw material composition includes:

[0006] Polypropylene resin: 80 - 99 parts

[0007] Radiation-resistant masterbatch: 1 - 20 parts

[0008] Nucleating agent: 0.05 - 0.5 parts

[0009] Antioxidant: 0.1 - 1 part

[0010] Light stabilizer: 0.1 - 1 part

[0011] Lubricant: 0.1 - 1 part

[0012] Acid absorbent: 0.05 - 0.5 parts

[0013] The polypropylene resin is selected from at least one of homopolypropylene, random copolymer polypropylene, and block copolymer polypropylene;

[0014] The polypropylene resin is in the form of powder or pellets, and has a melt index in the range of 1 - 200 g / 10 min at 230 °C and 2.16 kg.

[0015] The radiation-resistant masterbatch (RRP) is prepared by adding a multi-vinyl functional group monomer and a nano-inorganic powder to a polypropylene matrix and extruding and pelletizing through a twin-screw extruder; wherein, 80 - 90 parts of polypropylene, 5 - 15 parts of multi-vinyl functional group monomer, and 1 - 10 parts of nano-inorganic powder. Preferably, 85 parts of polypropylene, 10 parts of multi-vinyl functional group monomer, and 5 parts of nano-inorganic powder;

[0016] The multi-vinyl functional group monomer is selected from at least one of 1,4-butanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, and pentaerythritol tetramethacrylate;

[0017] The nano-inorganic powder is selected from at least one of nano-zinc oxide, nano-titanium dioxide, nano-cerium dioxide, nano-tungsten trioxide, and nano-tin dioxide.

[0018] The nucleating agent is selected from at least one of calcium carbonate, talc powder, silicon dioxide, 3988, TMB-5, NA-11, NA-21, NA-71, HPN900ei, NX8000, NU-100, and WBG-II.

[0019] The antioxidant is a compound combination of a hydroperoxide decomposer and an alkyl radical scavenger;

[0020] The hydroperoxide decomposer is selected from at least one of DMTDP, DLTDP, DSTDP, SE-10, 626, 618, 168, and P-EPQ;

[0021] The alkyl radical scavenger is selected from at least one of 501 and FS042.

[0022] The light stabilizer is a hindered amine type light stabilizer, preferably selected from at least one of 770, 944, 622, 5050, 123, 228, 144, and 202.

[0023] The lubricant is selected from at least one of ethylene bisstearamide, polyethylene wax, oleic acid amide, and erucic acid amide.

[0024] The acid absorbent is selected from at least one of calcium stearate and magnesium aluminum hydrotalcite.

[0025] The present invention also provides a method for preparing an irradiated sterilized polypropylene composition. The PP resin, radiation-resistant masterbatch, nucleating agent, antioxidant, light stabilizer, and lubricant are added to a high-speed mixer according to a ratio. After mixing evenly, they are added to the hopper of a twin-screw extruder. The temperatures of each zone of the extruder and the screw speed are set, and melting extrusion and granulation are carried out to obtain composition particles.

[0026] The temperature of the twin-screw extruder is 170-230 °C, and the screw speed is 100-400 r / min. Preferably, the temperature of the extruder is 190-210 °C, and the screw speed is 200-250 r / min.

[0027] Compared with the prior art, the main advantages of the present invention include:

[0028] 1) The additives in the formula have no color-forming groups, and the color change of polypropylene after irradiated sterilization is small;

[0029] 2) Adding multi-vinyl functional group monomers to the formulation can capture polypropylene tertiary carbon free radicals during the irradiation sterilization process to undergo cross-linking and chain extension reactions, balancing the irradiation degradation of the polypropylene matrix; meanwhile, the required addition content of the multi-vinyl functional group monomers is low and does not affect the mechanical strength of the polypropylene matrix;

[0030] 3) By adding inorganic oxide powders, through the synergistic effect with multi-vinyl functional group monomers, the radiation resistance of polypropylene can be further significantly improved. Embodiment

[0031] The following further elaborates the present invention in conjunction with specific embodiments. 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 operating methods without specific conditions noted in the following embodiments are generally in accordance with conventional conditions or in accordance with the conditions recommended by the manufacturer.

[0032] The raw material compositions of each embodiment are in parts by mass as shown in Table 1, and the preparation method is as follows:

[0033] Add each raw material component according to the ratio in Table 1 to a high-speed mixer, mix evenly and then add it to a twin-screw extruder. Set the extruder temperature to 190 - 210 °C, the screw speed to 200 r / min, the feeding frequency to 10 Hz, and pelletize after water bath cooling to obtain polypropylene pellets.

[0034] Inject the above polypropylene pellets to prepare standard mechanical splines, and irradiate the polypropylene pellets and splines with an electron beam generated by an electron accelerator. Set the irradiation dose to 25 kGy and 50 kGy, and test the relevant properties of the samples before and after irradiation.

[0035] Table 1

[0036] Component / Specification Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Comparative Example 3 Polypropylene Resin / Random Copolymer PP 94.1 89.1 84.1 94.1 84.1 84.1 99.1 89 59.1 Irradiation-Resistant Masterbatch / RRP-1 5 10 15 5 - - - 10 40 Irradiation-Resistant Masterbatch / RRP-2 - - - - 15 - - - - Irradiation-Resistant Masterbatch / RRP-3 - - - - - 15 - - - Nucleating Agent / HPN 900ei 0.2 0.2 0.2 - 0.2 0.2 0.2 0.2 0.2 Nucleating Agent / TMB-5 - - - 0.2 - - - - - Antioxidant / 626 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 Antioxidant / 626 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Antioxidant / 1076 (Hindered Phenol) - - - - - - - 0.1 - Light Stabilizer / 622 0.2 0.2 0.2 - - - 0.2 0.2 0.2 Light Stabilizer / 202 - - - 0.2 0.2 0.2 - - - Lubricant / Ethylene Bisstearamide 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 Acid Absorbent / Magnesium Aluminum Hydrotalcite 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1

[0037] The RRP-1 masterbatch contains 10 parts of trimethylolpropane triacrylate and 5 parts of nano-tin dioxide; the RRP-2 masterbatch contains 10 parts of trimethylolpropane triacrylate. The RRP-3 masterbatch contains 10 parts of trimethylolpropane triacrylate and 5 parts of nano-zinc oxide.

[0038] Test the samples prepared in the above embodiments and comparative examples, and the test data are listed in Table 2. The melt index is tested according to GB / T 3682.1, the tensile strength and elongation at break are tested according to GB / T 1040.2, the flexural strength and flexural modulus are tested according to GB / T 9341, the notched izod impact strength of the simply supported beam is tested according to GB / T 1043.2, and the yellowness index is tested according to ASTM D1925.

[0039] Table 2

[0040] Example 1 Example 1 Example 1 Example 2 Example 2 Example 2 Example 3 Example 3 Example 3 Example 4 Example 4 Example 4 Example 5 Example 5 Example 5 Example 6 Example 6 Example 6 Comparative Example 1 Comparative Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 2 Comparative Example 2 Comparative Example 3 Comparative Example 3 Comparative Example 3 Irradiation Dose / KGy 0 25 50 0 25 50 0 25 50 0 25 50 0 25 50 0 25 50 0 25 50 0 25 50 0 25 50 Melt Index / g / 10min 22 33 45 22 28 36 24 26 23 25 34 43 22 39 53 25 31 38 18 59 112 21 26 35 31 Not Detectable Not Detectable Tensile Strength / MPa 31 32 34 32 34 34 32 33 34 34 35 36 31 32 32 33 34 33 34 33 34 32 33 33 28 31 32 Elongation at Break / % 341 275 257 306 289 276 314 305 320 316 245 206 327 260 246 308 289 285 338 206 97 324 301 288 246 193 113 Flexural Strength / MPa 32 33 35 34 34 35 35 35 36 36 37 38 33 34 34 36 35 37 36 36 37 33 33 34 29 33 33 Flexural Modulus / GPa 1.15 1.19 1.20 1.18 1.20 1.23 1.21 1.25 1.23 1.28 1.32 1.35 1.10 1.15 1.25 1.25 1.28 1.29 1.16 1.19 1.23 1.17 1.20 1.22 1.05 1.13 1.20 <![CDATA[Notched impact strength of simply supported beam / KJ / m 2 > 7.8 7.6 7.1 7.6 7.3 7.1 7.7 7.6 7.6 8.0 7.6 7.2 7.9 7.2 6.8 7.7 7.2 7.0 7.8 6.4 4.7 7.9 7.5 7.3 7.4 6.5 6.1 Yellow Index 1.31 1.39 1.43 1.40 1.48 1.51 1.43 1.48 1.52 1.32 1.32 1.46 1.25 1.31 1.38 1.21 1.23 1.27 1.21 1.26 1.34 1.44 4.11 5.87 1.35 1.41 1.48

[0041] According to the results in Table 2, for Examples 1 to 5, the polypropylene composition provided by the present invention for irradiation sterilization has good irradiation resistance. After irradiation with 25 kGy, the change in yellowness index is less than 0.1, and after irradiation with 50 kGy, the change in yellowness index is less than 0.15; and there is no obvious deterioration in various mechanical properties. In particular, as the content of the irradiation-resistant masterbatch gradually increases (Examples 1 to 3), the changes in melt index and elongation at break before and after irradiation of the material are very small and gradually tend to be stable, indicating that the polyvinyl functional group monomers in the irradiation-resistant masterbatch undergo crosslinking and chain extension reactions during irradiation, thereby balancing the irradiation degradation reaction of polypropylene, reducing the degree of chain scission of the polymer chain segments, and maintaining the original basic physical properties. In addition, in the formulation of Example 5, the irradiation-resistant masterbatch does not contain nano-inorganic powder, and compared with Example 3, the elongation at break and notched impact strength after irradiation decrease to a certain extent, indicating that the synergistic effect of nano-inorganic powder and polyvinyl functional group monomers can further improve the irradiation resistance of polypropylene materials. In the formulation of Example 6, the irradiation-resistant masterbatch contains both vinyl functional group monomers and nano-zinc oxide. Compared with using nano-tin dioxide in Example 3, the change in yellowness index after irradiation is smaller when using nano-zinc oxide, but the effect of maintaining mechanical properties such as elongation at break and notched impact strength after irradiation is not as good as using nano-tin dioxide.

[0042] Comparing Comparative Example 1 with Examples 1 to 3, it can be seen that when the irradiation-resistant masterbatch is not added, the melt index of the irradiated polypropylene material increases by several times. After irradiation with 25 kGy, the melt index is 3.3 times that before irradiation, and after irradiation with 50 kGy, the melt index is 6.2 times that before irradiation; correspondingly, the elongation at break and notched impact strength after irradiation decrease significantly.

[0043] Comparing Comparative Example 2 with Example 2, it can be seen that when a hindered phenol antioxidant is added, although the melt index and various mechanical properties of the material change little before and after irradiation, the yellowness index after irradiation increases significantly, and the appearance turns yellow seriously, which is not suitable for irradiation sterilization products.

[0044] Comparing Comparative Example 3 with Examples 1 to 3, it can be seen that in Comparative Example 3, the content of the irradiation-resistant masterbatch exceeds the range specified in this patent, and the melt index of the prepared polypropylene material cannot be measured after irradiation. This is because an excessive amount of polyvinyl functional group monomers are added, and the crosslinking reaction completely dominates during irradiation, resulting in a three-dimensional crosslinked network structure of the polymer chain segments, a decrease in the toughness of the material, and a certain degree of decrease in the notched impact strength.

[0045] The present invention provides a polypropylene composition for irradiation sterilization and its preparation method. There is no irradiation color-causing auxiliary in the formula, and a multi-vinyl functional group monomer and a nano-inorganic powder are added in the form of a radiation-resistant masterbatch, so as to improve the resistance of polypropylene to high-energy rays through synergistic effects. The prepared polypropylene composition has a small change in yellowness index after irradiation, and high retention rates of physical properties and mechanical properties such as melt index, elongation at break, and notched impact strength, and has excellent irradiation resistance characteristics, and is particularly suitable for manufacturing polypropylene medical device products, consumables, medical non-woven fabrics and other products that can be irradiated and sterilized.

[0046] 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 the present application.

Claims

1. A polypropylene composition for irradiation sterilization, characterized in that, The raw material composition, by mass parts, includes: Polypropylene resin: 80 - 99 parts Irradiation-resistant masterbatch: 1 - 20 parts Nucleating agent: 0.05 - 0.5 part Antioxidant: 0.1 - 1 part Light stabilizer: 0.1 - 1 part Lubricant: 0.1 - 1 part Acid absorbent: 0.05 - 0.5 part; The irradiation-resistant masterbatch (RRP) is prepared by twin-screw extrusion granulation with polypropylene as the matrix, adding multi-vinyl functional group monomers and nano-inorganic powders. The multi-vinyl functional group monomers are selected from at least one of 1,4-butanediol diacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, triallyl cyanurate, triallyl isocyanurate, pentaerythritol tetramethacrylate. The nano-inorganic powders are selected from at least one of nano-zinc oxide, nano-titanium dioxide, nano-cerium dioxide, nano-tungsten trioxide, nano-tin dioxide. The components of the irradiation-resistant masterbatch are: 80 - 90 parts of polypropylene, 5 - 15 parts of multi-vinyl functional group monomers, and 1 - 10 parts of nano-inorganic powders.

2. The polypropylene composition for irradiation sterilization according to claim 1, characterized in that, The polypropylene resin is selected from at least one of homopolypropylene, random copolymer polypropylene, and block copolymer polypropylene. The polypropylene resin is in the form of powder or pellets, and has a melt index in the range of 1 - 200 g / 10 min under the conditions of 230 °C and 2.16 kg.

3. The polypropylene composition for irradiation sterilization according to claim 1, characterized in that, The nucleating agent is selected from at least one of calcium carbonate, talc, silica, 3988, TMB-5, NA-11, NA-21, NA-71, HPN900ei, NX8000, NU-100, WBG-II.

4. The polypropylene composition for irradiation sterilization according to claim 1, characterized in that, The antioxidant is a compound combination of a hydroperoxide decomposer and an alkyl radical scavenger. The hydroperoxide decomposer is selected from at least one of DMTDP, DLTDP, DSTDP, SE-10, 626, 618, 168, P-EPQ. The alkyl radical scavenger is selected from at least one of 501 and FS042.

5. The polypropylene composition for irradiation sterilization according to claim 1, wherein The light stabilizer is selected from hindered amine light stabilizers.

6. The polypropylene composition for irradiation sterilization according to claim 5, wherein The hindered amine light stabilizers are selected from at least one of 770, 944, 622, 5050, 123, 228, 144, 202.

7. The polypropylene composition for irradiation sterilization according to claim 1, characterized in that, The lubricant is selected from at least one of ethylene bisstearamide, polyethylene wax, oleic acid amide, and erucic acid amide.

8. The polypropylene composition for irradiation sterilization according to claim 1, wherein The acid absorbent is selected from at least one of calcium stearate and magnesium aluminum hydrotalcite.

9. A preparation method for a polypropylene composition for irradiation sterilization according to any one of claims 1 to 8, characterized in that, Add the polypropylene resin, irradiation-resistant masterbatch, nucleating agent, antioxidant, light stabilizer, and lubricant into a high-speed mixer according to the ratio, mix evenly, then add them into the hopper of a twin-screw extruder, set the temperature of each zone of the extruder and the screw speed, and melt-extrude and granulate to obtain the composition particles. The temperature of the twin-screw extruder is 170 - 230 °C, and the screw speed is 100 - 400 r / min.

10. The preparation method of the polypropylene composition for irradiation sterilization according to claim 9, characterized in that, Add the polypropylene resin, irradiation-resistant masterbatch, nucleating agent, antioxidant, light stabilizer, and lubricant into a high-speed mixer according to the ratio, mix evenly, then add them into the hopper of a twin-screw extruder, set the temperature of each zone of the extruder and the screw speed, and melt-extrude and granulate to obtain the composition particles. The temperature of the twin-screw extruder is 190 - 210 °C, and the screw speed is 200 - 250 r / min.