High-barrier polypropylene composite material and preparation method thereof

Abstract

The invention relates to the technical field of polypropylene, and discloses a high-barrier polypropylene composite material and a preparation method thereof, the high-barrier polypropylene composite material comprises 55-80 parts by weight of polypropylene, 20-45 parts by weight of cardanol modified polystyrene, and 1.2-2 parts by weight of maleic anhydride grafted polypropylene; according to the invention, an alkyl long chain of cardanol is introduced into a side chain of polystyrene, and the alkyl long chain and polypropylene are subjected to a physical chain winding effect, so that a tight physical crosslinking is formed, the crosslinking density of a polypropylene molecular chain is improved, the water vapor permeability is reduced, and the barrier property is improved. The cardanol modified polystyrene contains hydroxyl groups and reacts with the compatilizer maleic anhydride grafted polypropylene, so that the compatibility between the polystyrene and the polypropylene is improved, the polystyrene and the polypropylene form an alloy system, higher mechanical properties are shown, and the tensile strength and the bending strength are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of polypropylene, and specifically relates to a high-barrier polypropylene composite material and a preparation method thereof. Background Art

[0002] Due to its good chemical stability, electrical insulation, transparency and other properties, polypropylene is widely used in the fields of food and drug packaging, automotive parts, building materials, etc. Improving the barrier properties of polypropylene to water vapor, oxygen, etc. can make polypropylene packaging materials have better moisture-proof and oxygen-barrier effects, can extend the shelf life of products, and reduce transportation costs, etc.

[0003] Traditional polypropylene materials have problems such as low mechanical strength. Compounding polypropylene with high molecular resins such as nylon, polystyrene, and polycarbonate to form alloy materials has better mechanical strength and toughness. However, there are large differences in the chemical structures of polystyrene and polypropylene, and their compatibility is very poor. Usually, a compatibilizer needs to be added. Chinese patent application document CN117887175A discloses a high weather resistance and yellowing resistance PP / PS alloy material for automotive interiors. By blending polypropylene, polystyrene, SBS and other compatibilizers, a high weather resistance and yellowing resistance alloy material is obtained. However, this patent does not improve the water vapor barrier and other properties of polypropylene materials. Summary of the Invention

[0004] The present invention solves the problem of low mechanical strength of polypropylene materials and at the same time improves the barrier properties of polypropylene.

[0005] The technical solution of the present invention: A high-barrier polypropylene composite material and a preparation method, including 55-80 parts by weight of polypropylene, 20-45 parts by weight of cardanol-modified polystyrene, 1.2-2 parts by weight of maleic anhydride-grafted polypropylene, and 0.15-0.3 parts by weight of antioxidant.

[0006] The preparation method is: Mix polypropylene, cardanol-modified polystyrene, maleic anhydride-grafted polypropylene, and antioxidant, add them to a twin-screw extruder, melt and extrude, cool and pelletize to obtain a high-barrier polypropylene composite material.

[0007] Further, the main shaft speed of the twin-screw extruder is 100-200 r / min; the temperature of zones 1-6 is 170-215 °C.

[0008] Further, the antioxidant is a hindered phenol antioxidant or a phosphite antioxidant.

[0009] Further, the preparation method of cardanol-modified polystyrene is: (1) Add polystyrene to chloroform. After stirring, dropwise add a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid. After the reaction, perform purification treatment. Pour the solution into water, stir and remove the aqueous phase. Add the chloroform organic phase to isopropanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide, stir and then add isopropanol to precipitate a solid. Filter and dry to obtain nitrated polystyrene.

[0010] (2) Add stannous chloride to concentrated hydrochloric acid. After stirring, dropwise add a solution of nitrated polystyrene in N,N-dimethylformamide. After the reaction, perform purification treatment. Pour the solution into ethanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide, stir and then add ethanol to precipitate a solid. Filter and dry to obtain aminated polystyrene. The reaction formula is: .

[0011] (3) Add 100 parts by weight of aminated polystyrene to the reaction solvent. After stirring, add 8 - 25 parts by weight of cardanol glycidyl ether. After stirring and reacting, pour the solution into ethanol, wash with ethanol after filtration, and dry to obtain cardanol-modified polystyrene. The reaction formula is: .

[0012] Further, the reaction temperature in (1) is 30 - 40 °C, and the reaction time is 3 - 6 h.

[0013] Further, the reaction temperature in (2) is 90 - 100 °C, and the reaction time is 12 - 18 h.

[0014] Further, the reaction solvent in (3) is N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran or 1,4-dioxane.

[0015] Further, the reaction temperature in (3) is 45 - 60 °C, and the reaction time is 12 - 18 h.

[0016] Beneficial technical effects: In the present invention, aminated polystyrene and cardanol glycidyl ether are reacted to obtain polystyrene containing hydroxyl and cardanol structures, and then blended and pelletized with polypropylene, maleic anhydride grafted polypropylene, etc. to obtain a high-barrier polypropylene composite material. An alkyl long chain of cardanol is introduced into the side chain of polystyrene. The alkyl long chain is similar to the molecular chain of polypropylene, and the two undergo physical chain entanglement to form a tight physical crosslinking, which improves the crosslinking density of the polypropylene molecular chain and is beneficial to reducing the water vapor transmission performance. Moreover, the main chain of the polystyrene molecule in the cardanol-modified polystyrene has strong hydrophobicity, and the cardanol in the side chain also contains a hydrophobic benzene ring and alkyl chain. Under the synergistic effect, the hydrophobicity of the polypropylene material is improved, the water vapor transmission rate is significantly reduced, and the moisture-proof and barrier properties are improved.

[0017] In the present invention, an alkyl long chain is introduced into the side chain of polystyrene, improving its compatibility with polypropylene. Moreover, the cardanol-modified polystyrene contains hydroxyl groups, which react with maleic anhydride grafted polypropylene as a compatibilizer during the melt blending process. Under the action of the compatibilizer, the compatibility between polystyrene and polypropylene is further improved, and the two form an alloy system, showing higher mechanical properties and increased tensile strength and flexural strength.

[0018] Polystyrene itself has a high thermal decomposition temperature, and the cardanol introduced into the side chain also contains a heat-resistant benzene ring structure. The cardanol-modified polystyrene is uniformly dispersed in the polypropylene group, which can increase the initial thermal decomposition temperature and heat resistance of the polypropylene material. Detailed implementation mode

[0019] To facilitate the understanding of the present invention, the following will further illustrate the present invention in combination with embodiments. It should be understood that the following embodiments are only for better understanding the present invention, and do not mean that the present invention is limited only to the following embodiments.

[0020] The following polypropylene model PT231M is purchased from Suzhou Shengxinlong Plastic Co., Ltd. The polystyrene model 525B is purchased from Jinan Yueyang Chemical Co., Ltd. The maleic anhydride grafted polypropylene model CA100 is purchased from Dongguan Yingsheng Plastic Chemical Co., Ltd.

[0021] Example 1: (1) Add 100 g of polystyrene to 2 L of chloroform, stir and then dropwise add a mixed acid solution of 20 mL of concentrated sulfuric acid with a mass fraction of 98% and 70 mL of concentrated nitric acid with a mass fraction of 68%. Heat to 35 °C and stir and react for 4 h. Pour the solution into 4 L of water, stir and remove the aqueous phase. Add the chloroform organic phase to isopropanol, precipitate, filter, add the product to N,N-dimethylformamide, stir, add isopropanol to precipitate, filter, and dry to obtain nitrated polystyrene.

[0022] (2) Add 7.4 g of stannous chloride to 1.5 L of concentrated hydrochloric acid with a mass fraction of 36%, stir and then dropwise add 0.9 L of an N,N-dimethylformamide solution containing 100 g of nitrated polystyrene. Heat to 90 °C and stir and react for 18 h. Pour the solution into ethanol, precipitate, filter, add the product to N,N-dimethylformamide, stir, add ethanol to precipitate, filter, and dry to obtain amino polystyrene.

[0023] (3) Add 200 g of amino polystyrene to 4 L of tetrahydrofuran, stir and then add 26 g of cardanol glycidyl ether. Heat to 60 °C, stir and reflux for 12 h. Pour the solution into ethanol, filter, wash with ethanol, and dry to obtain cardanol-modified polystyrene.

[0024] (4) Mix 800 g of polypropylene, 200 g of cardanol-modified polystyrene, 12 g of maleic anhydride-grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076, add them to a twin-screw extruder, with the main shaft speed of 150 r / min, and the temperatures of zones 1 - 6 being 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Melt and extrude, then cool and pelletize to obtain a high-barrier polypropylene composite material.

[0025] Example 2: (1) Add 100 g of polystyrene to 2.5 L of chloroform. After stirring, dropwise add a mixed acid solution of 25 mL of concentrated sulfuric acid with a mass fraction of 98% and 80 mL of concentrated nitric acid with a mass fraction of 68%. Heat to 40 °C and stir for 4 h. Pour the solution into 5 L of water, stir and remove the aqueous phase. Add the chloroform organic phase to isopropanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide, stir and then add isopropanol to precipitate a solid. Filter and dry to obtain nitrated polystyrene.

[0026] (2) Add 10 g of stannous chloride to 1.8 L of concentrated hydrochloric acid with a mass fraction of 36%. After stirring, dropwise add 1 L of an N,N-dimethylformamide solution containing 100 g of nitrated polystyrene. Heat to 100 °C and stir for 12 h. Pour the solution into ethanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide, stir and then add ethanol to precipitate a solid. Filter and dry to obtain aminated polystyrene.

[0027] (3) Add 200 g of aminated polystyrene to 3.5 L of 1,4-dioxane. After stirring, add 50 g of cardanol glycidyl ether. Heat to 50 °C and stir for 18 h. Pour the solution into ethanol, filter and wash with ethanol, then dry to obtain cardanol-modified polystyrene.

[0028] (4) Mix 700 g of polypropylene, 300 g of cardanol-modified polystyrene, 14 g of maleic anhydride-grafted polypropylene, and 3 g of hindered phenol antioxidant 1076, add them to a twin-screw extruder, with the main shaft speed of 200 r / min, and the temperatures of zones 1 - 6 being 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Melt and extrude, then cool and pelletize to obtain a high-barrier polypropylene composite material.

[0029] Example 3: (1) Add 100 g of polystyrene to 2 L of chloroform. After stirring, add dropwise a mixed acid solution of 20 mL of concentrated sulfuric acid with a mass fraction of 98% and 70 mL of concentrated nitric acid with a mass fraction of 68%. Heat to 40 °C and stir for reaction for 3 h. Pour the solution into 4 L of water. After stirring, remove the aqueous phase. Add the chloroform organic phase to isopropanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide. After stirring, add isopropanol to precipitate a solid. Filter and dry to obtain nitrated polystyrene.

[0030] (2) Add 6 g of stannous chloride to 1.4 L of concentrated hydrochloric acid with a mass fraction of 36%. After stirring, add dropwise 0.8 L of an N,N-dimethylformamide solution containing 100 g of nitrated polystyrene. Heat to 95 °C and stir for reaction for 12 h. Pour the solution into ethanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide. After stirring, add ethanol to precipitate a solid. Filter and dry to obtain aminated polystyrene.

[0031] (3) Add 200 g of aminated polystyrene to 2 L of N,N-dimethylacetamide. After stirring, add 16 g of cardanol glycidyl ether. Heat to 50 °C and stir for reaction for 12 h. Pour the solution into ethanol, wash with ethanol after filtration, and dry to obtain cardanol-modified polystyrene.

[0032] (4) Mix 600 g of polypropylene, 400 g of cardanol-modified polystyrene, 17 g of maleic anhydride-grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076. Add them to a twin-screw extruder. The main shaft rotation speed is 100 r / min, and the temperatures of zones 1-6 are 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Melt and extrude, and cool and pelletize with water to obtain a high-barrier polypropylene composite material.

[0033] Example 4: (1) Add 100 g of polystyrene to 2.5 L of chloroform. After stirring, add dropwise a mixed acid solution of 25 mL of concentrated sulfuric acid with a mass fraction of 98% and 80 mL of concentrated nitric acid with a mass fraction of 68%. Heat to 30 °C and stir for reaction for 6 h. Pour the solution into 5 L of water. After stirring, remove the aqueous phase. Add the chloroform organic phase to isopropanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide. After stirring, add isopropanol to precipitate a solid. Filter and dry to obtain nitrated polystyrene.

[0034] (2) Add 8.7 g of stannous chloride to 1.8 L of concentrated hydrochloric acid with a mass fraction of 36%. After stirring, add dropwise 1 L of an N,N-dimethylformamide solution containing 100 g of nitrated polystyrene. Heat to 90 °C and stir for 18 h. Pour the solution into ethanol to precipitate a solid. After filtration, add the product to N,N-dimethylformamide, stir, add ethanol to precipitate a solid again, filter, and dry to obtain amino-functionalized polystyrene.

[0035] (3) Add 200 g of amino-functionalized polystyrene to 2.5 L of N,N-dimethylformamide. After stirring, add 38 g of cardanol glycidyl ether. Heat to 45 °C and stir for 18 h. Pour the solution into ethanol, wash with ethanol after filtration, and dry to obtain cardanol-modified polystyrene.

[0036] (4) Mix 550 g of polypropylene, 450 g of cardanol-modified polystyrene, 20 g of maleic anhydride-grafted polypropylene, and 1.5 g of phosphite antioxidant 168. Add them to a twin-screw extruder with a main shaft rotation speed of 200 r / min. The temperatures in zones 1-6 are 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Melt and extrude, cool and pelletize to obtain a high-barrier polypropylene composite.

[0037] Comparative Example 1: (1) Mix 800 g of polypropylene, 12 g of maleic anhydride-grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076. Add them to a twin-screw extruder with a main shaft rotation speed of 150 r / min. The temperatures in zones 1-6 are 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Melt and extrude, cool and pelletize to obtain a polypropylene composite.

[0038] Comparative Example 2: (2) Mix 800 g of polypropylene, 200 g of polystyrene, 12 g of maleic anhydride-grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076. Add them to a twin-screw extruder with a main shaft rotation speed of 150 r / min. The temperatures in zones 1-6 are 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Melt and extrude, cool and pelletize to obtain a polypropylene composite.

[0039] Comparative Example 3: (1) Add 200 g of amino-functionalized polystyrene (prepared in Example 1) to 4 L of tetrahydrofuran. After stirring, add 26 g of octadecyl glycidyl ether. Heat to 60 °C, stir and carry out a reflux reaction for 12 h. Pour the solution into ethanol, wash with ethanol after filtration, and dry to obtain modified polystyrene.

[0040] (2) Mix 800 g of polypropylene, 200 g of modified polystyrene, 12 g of maleic anhydride grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076, add them to a twin-screw extruder, with the main shaft speed of 150 r / min, and the temperatures of zones 1-6 being 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Then perform melt extrusion and water-cooled pelletization to obtain a polypropylene composite material.

[0041] Comparative Example 4: (1) Mix 800 g of polypropylene, 200 g of cardanol-modified polystyrene (prepared in Example 1), and 2.2 g of hindered phenol antioxidant 1076, add them to a twin-screw extruder, with the main shaft speed of 150 r / min, and the temperatures of zones 1-6 being 170 °C, 200 °C, 215 °C, 215 °C, 210 °C, and 200 °C. Then perform melt extrusion and water-cooled pelletization to obtain a polypropylene composite material.

[0042] Inject the polypropylene composite material into a specimen by an injection molding machine. Test the tensile strength according to the method specified in the standard of GB / T 1040.1-2018. Test the flexural strength according to the method specified in the standard of GB / T 9341-2008.

[0043] Weigh 8 mg of the polypropylene composite material, place it in a thermogravimetric analyzer, and perform thermogravimetric analysis in a nitrogen atmosphere, with a heating rate of 10 °C / min and a temperature range of 30-700 °C.

[0044] After the polypropylene composite material is injection molded, press it into a thin sheet, and test the water vapor transmission rate according to the method specified in the standard of GB / T 1037-2021.

[0045] Table 1 Performance test of polypropylene composite materials , The water vapor transmission rate of the polypropylene composite of Comparative Example 1 is relatively large, and its barrier performance is poor. At the same time, its tensile strength and flexural strength are relatively low, its mechanical properties are poor, and the initial thermal decomposition temperature at a 5% mass loss is relatively low, and its heat resistance is poor. In the polypropylene of Examples 1-4, cardanol-modified polystyrene and compatibilizer maleic anhydride-grafted polypropylene are added. The alkyl long chain of cardanol is introduced into the side chain of polystyrene, which is similar to the molecular chain of polypropylene. The two undergo physical chain entanglement to form a tight physical crosslinking structure, which increases the crosslinking density of the polypropylene molecular chain and is conducive to reducing the water vapor transmission performance. The main chain of the polystyrene molecule in cardanol-modified polystyrene has strong hydrophobicity, and cardanol also contains hydrophobic benzene rings and alkyl chains. Under their synergistic effect, the hydrophobicity of the polypropylene material is improved, the water vapor transmission rate is significantly reduced, and the barrier performance is improved. At the same time, the alkyl long chain is introduced into the side chain of polystyrene, improving its compatibility with polypropylene. Moreover, cardanol-modified polystyrene contains hydroxyl groups, which react with the compatibilizer maleic anhydride-grafted polypropylene during the melt blending process. Under the action of the compatibilizer, the compatibility between polystyrene and polypropylene is further improved, and the two form an alloy system with higher mechanical properties, improving the tensile strength and flexural strength. At the same time, polystyrene itself has a high thermal decomposition temperature, and the introduced cardanol in the side chain also contains a heat-resistant benzene ring structure. The evenly dispersed cardanol-modified polystyrene in the polypropylene group can improve its heat resistance and has a higher initial thermal decomposition temperature.

[0046] In Comparative Example 2, ordinary polystyrene is added, which does not contain an alkyl long chain and cannot undergo physical chain entanglement with polypropylene, so a tight physical crosslinking structure is not formed, and the crosslinking density of the polypropylene molecular chain cannot be increased, resulting in a relatively large water vapor transmission rate and poor barrier performance. Moreover, polystyrene does not contain hydroxyl groups and cannot react with the compatibilizer maleic anhydride-grafted polypropylene, resulting in poor compatibility between polystyrene and polypropylene and poor mechanical properties of the composite material, with relatively low tensile strength and flexural strength.

[0047] In Comparative Example 3, aminated polystyrene is reacted with octadecyl glycidyl ether. Compared with cardanol glycidyl ether, octadecyl glycidyl ether does not contain hydrophobic and heat-resistant benzene ring structures, resulting in a slightly larger water vapor transmission rate of the polypropylene composite than that of Example 1 and an initial thermal decomposition temperature lower than that of Example 1.

[0048] Compared with Example 1, in Comparative Example 4, maleic anhydride-grafted polypropylene is not added, resulting in relatively low compatibility between cardanol-modified polystyrene and polypropylene, and relatively low tensile strength and flexural strength of the composite material. However, it is higher than those of Comparative Example 1 and Comparative Example 2, mainly because the alkyl long chain of cardanol is introduced into the side chain of polystyrene, which is similar to the molecular chain of polypropylene, and the two have a certain compatibility, which is conducive to improving the mechanical strength of the material.

[0049] It is easy to understand that the above embodiments are only examples for clear illustration, and do not mean that the present invention is limited thereto. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A high barrier polypropylene composite material, characterized in that: The high barrier polypropylene composite material comprises 55-80 parts by weight of polypropylene, 20-45 parts by weight of cardanol modified polystyrene, 1.2-2 parts by weight of maleic anhydride grafted polypropylene, and 0.15-0.3 parts by weight of antioxidant; The preparation method of the cardanol modified polystyrene is as follows: 100 parts by weight of amino polystyrene is added to a reaction solvent, 8-25 parts by weight of cardanol glycidyl ether is added after stirring, the solution is poured into ethanol after stirring for reaction, filtered, washed with ethanol, and dried to obtain the cardanol modified polystyrene.

2. The high barrier polypropylene composite material according to claim 1, characterized in that: The antioxidant is a hindered phenol antioxidant or a phosphite antioxidant.

3. The high barrier polypropylene composite material according to claim 1, characterized in that: The reaction solvent is N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran or 1,4-dioxane.

4. The high barrier polypropylene composite material according to claim 1, characterized in that: The reaction temperature is 45-60°C and the reaction time is 12-18h.

5. The high barrier polypropylene composite material according to claim 1, characterized in that: The preparation method of the amino polystyrene is: (1) adding polystyrene to chloroform, adding dropwise a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid after stirring, performing purification treatment after the reaction, precipitating a precipitate, filtering, and drying to obtain nitrated polystyrene; (2) Add stannous chloride to concentrated hydrochloric acid, stir and then dropwise add a solution of nitrated polystyrene in N,N-dimethylformamide. After the reaction, perform purification treatment to precipitate the precipitate, filter and dry to obtain amino polystyrene.

6. The high barrier polypropylene composite material according to claim 1, characterized in that: The reaction temperature in (1) is 30-40°C and the reaction time is 3-6h.

7. The high barrier polypropylene composite material according to claim 1, characterized in that: The reaction temperature in (2) is 90-100°C and the reaction time is 12-18h.

8. A method for preparing the high barrier polypropylene composite material according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: mixing polypropylene, cardanol-modified polystyrene, maleic anhydride-grafted polypropylene and an antioxidant, adding the mixture into a twin-screw extruder, performing melt extrusion, and water-cooling and pelletizing to obtain a high-barrier polypropylene composite material.

9. The method for preparing a high barrier polypropylene composite material according to claim 8, characterized in that: The main shaft speed of the twin-screw extruder is 100-200r / min; the temperature of zones 1-6 is 170-215°C.