High-barrier polypropylene composite material and preparation method thereof

Abstract

The application relates to the technical field of polypropylene, and discloses a high-barrier polypropylene composite material and a preparation method, the high-barrier polypropylene composite material comprising 55-80 parts by weight of polypropylene, 20-45 parts by weight of cashew phenol modified polystyrene and 1.2-2 parts by weight of maleic anhydride grafted polypropylene; alkyl long chains of cashew phenol are introduced into side chains of the polystyrene, physical chain entanglement occurs between the alkyl long chains and the polypropylene, tight physical crosslinking is formed, the crosslinking density of polypropylene molecular chains is improved, water vapor permeation performance is reduced, and the barrier property is improved. The cashew phenol modified polystyrene contains hydroxyl groups, reacts with the compatible agent maleic anhydride grafted polypropylene, the compatibility between the polystyrene and the polypropylene is improved, an alloy system is formed by the polystyrene and the polypropylene, higher mechanical properties are shown, and the tensile strength and the bending strength are improved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of polypropylene, in particular to a high-barrier polypropylene composite material and a preparation method thereof. BACKGROUND

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

[0003] Traditional polypropylene materials have the problem of low mechanical strength. The alloy material prepared by compounding polypropylene with high molecular resins such as nylon, polystyrene and polycarbonate has better mechanical strength and toughness, but there is a big difference in chemical structure between polystyrene and polypropylene, and the compatibility of the two is very poor, so a compatibilizer is usually needed. Chinese patent application file CN117887175A discloses a high-weather-resistant and anti-yellowing PP / PS alloy material for automotive interior decoration, which blends polypropylene, polystyrene, SBS and other compatibilizers to obtain a high-weather-resistant and anti-yellowing alloy material, but the patent does not improve the water vapor barrier properties of polypropylene materials. SUMMARY

[0004] The application solves the problem of low mechanical strength of polypropylene materials and improves the barrier properties of polypropylene.

[0005] The technical scheme of the application is a high-barrier polypropylene composite material and a preparation method, which comprises 55-80 parts by weight of polypropylene, 20-45 parts by weight of cashew phenol modified polystyrene, 1.2-2 parts by weight of maleic anhydride grafted polypropylene and 0.15-0.3 parts by weight of an antioxidant.

[0006] The preparation method is as follows: the polypropylene, cashew phenol modified polystyrene, maleic anhydride grafted polypropylene and antioxidant are mixed and added to a twin-screw extruder for melt extrusion, water cooling and granulation to obtain the high-barrier polypropylene composite material.

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

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

[0009] Further, the preparation method of the cashew phenol modified polystyrene is as follows:

[0010] (1) adding polystyrene into chloroform, after stirring, adding mixed acid solution of concentrated sulfuric acid and concentrated nitric acid dropwise, after reaction, purifying, pouring the solution into water, after stirring, removing the water phase, adding chloroform organic phase into isopropyl alcohol, precipitating the precipitate, after filtration, adding the product into N,N-dimethylformamide, after stirring, adding isopropyl alcohol to precipitate the precipitate, filtering, drying, obtaining nitro-poly-styrene.

[0011] (2) adding stannous chloride into concentrated hydrochloric acid, after stirring, adding N,N-dimethylformamide solution of nitro-poly-styrene dropwise, after reaction, purifying, pouring the solution into ethanol, precipitating the precipitate, after filtration, adding the product into N,N-dimethylformamide, after stirring, adding ethanol to precipitate the precipitate, filtering, drying, obtaining amino-poly-styrene. The reaction formula is:

[0012] .

[0013] (3) adding 100 parts by weight of amino-poly-styrene into reaction solvent, after stirring, adding 8-25 parts by weight of cardanol glycidyl ether, after stirring and reaction, pouring the solution into ethanol, after filtration, washing with ethanol, drying, obtaining cardanol modified polystyrene. The reaction formula is:

[0014] .

[0015] Further, the temperature of reaction in (1) is 30-40℃, and the reaction time is 3-6h.

[0016] Further, the temperature of reaction in (2) is 90-100℃, and the reaction time is 12-18h.

[0017] Further, the reaction solvent in (3) is N,N-dimethylformamide, N,N-dimethylacetamide, tetrahydrofuran or 1,4-dioxane.

[0018] Further, the temperature of reaction in (3) is 45-60℃, and the reaction time is 12-18h.

[0019] Beneficial technical effects: the amino polystyrene and cardanol glycidyl ether are reacted in the application to obtain polystyrene containing hydroxyl and cardanol structure, then the polystyrene is blended and granulated with polypropylene, maleic anhydride grafted polypropylene and the like to obtain high-barrier polypropylene composite. The side chain of polystyrene introduces alkyl long chain of cardanol, the alkyl long chain is similar to the molecular chain of polypropylene, physical chain entanglement occurs between the two, forming a close physical crosslinking, improving the crosslinking density of the molecular chain of polypropylene, which is beneficial to reduce the water vapor transmission performance, and the polystyrene molecular main chain in the cardanol modified polystyrene has strong hydrophobicity, and the side chain of cardanol also contains hydrophobic benzene ring and alkyl chain, which improves the hydrophobicity of the polypropylene material, significantly reduces the water vapor transmission amount, and improves the moisture-proof and barrier properties.

[0020] The side chain of polystyrene in the application introduces alkyl long chain, which improves the compatibility with polypropylene, and the cardanol modified polystyrene contains hydroxyl groups, which reacts with the compatibilizer maleic anhydride grafted polypropylene during the melt blending process, and the compatibility between polystyrene and polypropylene is further improved under the action of the compatibilizer, forming an alloy system, which exhibits higher mechanical properties, improving the tensile strength and bending strength.

[0021] Polystyrene itself has a high thermal decomposition temperature, and the side chain introduces cardanol which also contains heat-resistant benzene ring structure, so that the cardanol modified polystyrene uniformly dispersed in the polypropylene group can improve the initial thermal decomposition temperature and heat resistance of the polypropylene material. DETAILED DESCRIPTION

[0022] In order to facilitate the understanding of the present application, the present application will be further described below in combination with examples. It should be understood that the following examples are only for better understanding of the present application, and do not mean that the present application is limited to the following examples.

[0023] The following polypropylene model PT231M is purchased from Suzhou Shengxinlong Plastic Co., Ltd. Polystyrene model 525B is purchased from Jinan Yueyang Chemical Co., Ltd. Maleic anhydride grafted polypropylene model CA100 is purchased from Dongguan Ying Sheng Plastic Chemical Co., Ltd.

[0024] Example 1: (1) 100g of polystyrene is added to 2L of chloroform, after stirring, 20mL of 98% concentrated sulfuric acid and 70mL of 68% concentrated nitric acid mixed acid solution are added dropwise, heated to 35℃, and stirred for 4h. The solution is poured into 4L of water, stirred, and the water phase is removed. The chloroform organic phase is added to isopropyl alcohol, the precipitate is separated out, the product is added to N,N-dimethylformamide after filtration, isopropyl alcohol is added after stirring to separate out the precipitate, and the product is obtained after filtration and drying.

[0025] (2) To 1.5 L of 36% concentrated hydrochloric acid, 7.4 g of stannous chloride was added, and after stirring, 0.9 L of N,N-dimethylformamide solution containing 100 g of nitro-polyphenylstyrene was added dropwise. The solution was heated to 90°C and stirred for 18 h. The solution was poured into ethanol to precipitate the product. The product was added to N,N-dimethylformamide, stirred, and then ethanol was added to precipitate the product. The product was filtered, dried, and then obtained as amino-polyphenylstyrene.

[0026] (3) To 4 L of tetrahydrofuran, 200 g of amino-polyphenylstyrene was added, and after stirring, 26 g of cardanol glycidyl ether was added. The solution was heated to 60°C, stirred and refluxed, and then condensed for 12 h. The solution was poured into ethanol, filtered, and then washed with ethanol. The product was dried to obtain cardanol-modified polyphenylstyrene.

[0027] (4) 800 g of polypropylene, 200 g of cardanol-modified polyphenylstyrene, 12 g of maleic anhydride grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076 were mixed and added to a twin-screw extruder. The main shaft was rotated at 150 r / min, and the temperatures of zones 1-6 were 170°C, 200°C, 215°C, 215°C, 210°C, and 200°C, respectively. The mixture was melt-extruded, water-cooled, and pelletized to obtain a high-barrier polypropylene composite material.

[0028] Example 2: (1) To 2.5 L of chloroform, 100 g of polystyrene was added, and after stirring, 25 mL of 98% concentrated sulfuric acid and 80 mL of 68% concentrated nitric acid were added dropwise. The solution was heated to 40°C and stirred for 4 h. The solution was poured into 5 L of water, stirred, and then the aqueous phase was removed. The chloroform organic phase was added to isopropyl alcohol to precipitate the product. The product was added to N,N-dimethylformamide, stirred, and then isopropyl alcohol was added to precipitate the product. The product was filtered, dried, and then obtained as nitro-polyphenylstyrene.

[0029] (2) To 1.8 L of 36% concentrated hydrochloric acid, 10 g of stannous chloride was added, and after stirring, 1 L of N,N-dimethylformamide solution containing 100 g of nitro-polyphenylstyrene was added dropwise. The solution was heated to 100°C and stirred for 12 h. The solution was poured into ethanol to precipitate the product. The product was added to N,N-dimethylformamide, stirred, and then ethanol was added to precipitate the product. The product was filtered, dried, and then obtained as amino-polyphenylstyrene.

[0030] (3) To 3.5 L of 1,4-dioxane, 200 g of amino-polyphenylstyrene was added, and after stirring, 50 g of cardanol glycidyl ether was added. The solution was heated to 50°C and stirred for 18 h. The solution was poured into ethanol, filtered, and then washed with ethanol. The product was dried to obtain cardanol-modified polyphenylstyrene.

[0031] (4) 700 g of polypropylene, 300 g of cashew phenol modified polystyrene, 14 g of maleic anhydride grafted polypropylene, and 3 g of hindered phenol antioxidant 1076 were mixed and added to a twin-screw extruder, the main shaft rotation speed was 200 r / min, the temperature of 1-6 zones was 170℃, 200℃, 215℃, 215℃, 210℃, 200℃, melt extrusion, water cooling and granulation, to obtain a high barrier polypropylene composite material.

[0032] Example 3: (1) 100 g of polystyrene was added to 2 L of chloroform, after stirring, 20 mL of 98% concentrated sulfuric acid and 70 mL of 68% concentrated nitric acid were added dropwise, heated to 40℃, stirred for 3 h, the solution was poured into 4 L of water, after stirring, the water phase was removed, the chloroform organic phase was added to isopropanol, the precipitate was separated, after filtration, the product was added to N,N-dimethylformamide, after stirring, isopropanol was added to precipitate the precipitate, filtered, and dried to obtain nitro-poly-styrene.

[0033] (2) 6 g of stannous chloride was added to 1.4 L of 36% concentrated hydrochloric acid, after stirring, 0.8 L of N,N-dimethylformamide solution containing 100 g of nitro-poly-styrene was added dropwise, heated to 95℃, stirred for 12 h, the solution was poured into ethanol, the precipitate was separated, after filtration, the product was added to N,N-dimethylformamide, after stirring, ethanol was added to precipitate the precipitate, filtered, and dried to obtain amino-poly-styrene.

[0034] (3) 200 g of amino-poly-styrene was added to 2 L of N,N-dimethylacetamide, after stirring, 16 g of cashew phenol glycidyl ether was added, heated to 50℃, stirred for 12 h, the solution was poured into ethanol, after filtration, ethanol was washed, and dried to obtain cashew phenol modified polystyrene.

[0035] (4) 600 g of polypropylene, 400 g of cashew phenol modified polystyrene, 17 g of maleic anhydride grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076 were mixed and added to a twin-screw extruder, the main shaft rotation speed was 100 r / min, the temperature of 1-6 zones was 170℃, 200℃, 215℃, 215℃, 210℃, 200℃, melt extrusion, water cooling and granulation, to obtain a high barrier polypropylene composite material.

[0036] Example 4: (1) 100 g of polystyrene was added to 2.5 L of chloroform, after stirring, 25 mL of 98% concentrated sulfuric acid and 80 mL of 68% concentrated nitric acid were added dropwise, heated to 30℃, stirred for 6 h, the solution was poured into 5 L of water, after stirring, the water phase was removed, the chloroform organic phase was added to isopropanol, the precipitate was separated, after filtration, the product was added to N,N-dimethylformamide, after stirring, isopropanol was added to precipitate the precipitate, filtered, and dried to obtain nitro-poly-styrene.

[0037] (2) To 1.8 L of 36% mass fraction concentrated hydrochloric acid, 8.7 g of stannous chloride was added, after stirring, 1 L of N,N-dimethylformamide solution containing 100 g of nitro-polyphenylethylene was added dropwise, heated to 90°C, and stirred for 18 h. The solution was poured into ethanol, and the precipitate was separated out. After filtration, the product was added to N,N-dimethylformamide, stirred, and then ethanol was added to separate out the precipitate. After filtration, drying was performed to obtain aminopolyphenylethylene.

[0038] (3) To 2.5 L of N,N-dimethylformamide, 200 g of aminopolyphenylethylene was added, after stirring, 38 g of cardanol glycidyl ether was added, heated to 45°C, and stirred for 18 h. The solution was poured into ethanol, and after filtration, ethanol was washed, and drying was performed to obtain cardanol-modified polyphenylethylene.

[0039] (4) 550 g of polypropylene, 450 g of cardanol-modified polyphenylethylene, 20 g of maleic anhydride grafted polypropylene, and 1.5 g of phosphite antioxidant 168 were mixed, and added to a twin-screw extruder. The main shaft rotation speed was 200 r / min, and the temperatures of zones 1-6 were 170°C, 200°C, 215°C, 215°C, 210°C, and 200°C. Melting extrusion was performed, and water-cooled pelletization was performed to obtain a high-barrier polypropylene composite material.

[0040] Comparative Example 1: (1) 800 g of polypropylene, 12 g of maleic anhydride grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076 were mixed, and added to a twin-screw extruder. The main shaft rotation speed was 150 r / min, and the temperatures of zones 1-6 were 170°C, 200°C, 215°C, 215°C, 210°C, and 200°C. Melting extrusion was performed, and water-cooled pelletization was performed to obtain a polypropylene composite material.

[0041] Comparative Example 2: (2) 800 g of polypropylene, 200 g of polystyrene, 12 g of maleic anhydride grafted polypropylene, and 2.2 g of hindered phenol antioxidant 1076 were mixed, and added to a twin-screw extruder. The main shaft rotation speed was 150 r / min, and the temperatures of zones 1-6 were 170°C, 200°C, 215°C, 215°C, 210°C, and 200°C. Melting extrusion was performed, and water-cooled pelletization was performed to obtain a polypropylene composite material.

[0042] Comparative Example 3: (1) To 4 L of tetrahydrofuran, 200 g of aminopolyphenylethylene (prepared according to Example 1) was added, after stirring, 26 g of octadecyl glycidyl ether was added, heated to 60°C, and stirred and condensed to reflux for 12 h. The solution was poured into ethanol, and after filtration, ethanol was washed, and drying was performed to obtain modified polyphenylethylene.

[0043] (2) Mix 800g polypropylene, 200g modified polystyrene, 12g maleic anhydride grafted polypropylene and 2.2g hindered phenolic antioxidant 1076 and add them to a twin-screw extruder. The spindle speed is 150r / min and the temperatures of zones 1-6 are 170℃, 200℃, 215℃, 215℃, 210℃ and 200℃, respectively. Melt extrusion is performed, followed by water cooling and pelletizing to obtain polypropylene composite material.

[0044] Comparative Example 4: (1) 800g of polypropylene, 200g of cashew phenol modified polystyrene (prepared from Example 1) and 2.2g of hindered phenol antioxidant 1076 were mixed and added to a twin-screw extruder. The spindle speed was 150r / min and the temperatures of zones 1-6 were 170℃, 200℃, 215℃, 215℃, 210℃ and 200℃, respectively. The mixture was melt-extruded, water-cooled and pelletized to obtain a polypropylene composite material.

[0045] Polypropylene composite materials were injection molded to form test specimens. Tensile strength was tested according to the method specified in GB / T 1040.1-2018. Flexural strength was tested according to the method specified in GB / T 9341-2008.

[0046] Weigh 8 mg of polypropylene composite material and place it in a thermogravimetric analyzer. Perform thermogravimetric analysis in a nitrogen atmosphere with a heating rate of 10 °C / min and a temperature range of 30-700 °C.

[0047] After injection molding, the polypropylene composite material is pressed into thin sheets, and the water vapor transmission rate is tested according to the method specified in GB / T 1037-2021.

[0048] Table 1 Performance testing of polypropylene composites

[0049] ,

[0050] The polypropylene composite material in Comparative Example 1 exhibited high water vapor permeability and poor barrier properties. Furthermore, it had low tensile and flexural strengths, resulting in poor mechanical properties. Additionally, its initial thermal decomposition temperature (with a 5% mass loss) was low, indicating poor heat resistance. In Examples 1-4, cashew phenol-modified polystyrene and maleic anhydride-grafted polypropylene were added. The side chains of the polystyrene incorporated long alkyl chains of cashew phenol, similar to the molecular chains of polypropylene. This physical chain entanglement resulted in a tight physical cross-linking, increasing the cross-linking density of the polypropylene molecular chains and thus improving water vapor permeability. The polystyrene backbone in the cashew phenol-modified polystyrene possessed strong hydrophobicity, while cashew phenol also contained hydrophobic benzene rings and alkyl chains. Through synergistic action, the hydrophobicity of the polypropylene material was improved, significantly reducing water vapor permeability and enhancing barrier properties. Meanwhile, the introduction of long alkyl chains into the side chains of polystyrene improves its compatibility with polypropylene. Furthermore, the cashew phenol-modified polystyrene contains hydroxyl groups, which react with the compatibilizer maleic anhydride-grafted polypropylene during melt blending. Under the action of the compatibilizer, the compatibility between polystyrene and polypropylene is further improved, forming an alloy system with higher mechanical properties, including increased tensile and flexural strength. At the same time, polystyrene itself has a high thermal decomposition temperature, and the cashew phenol introduced into the side chains also contains a heat-resistant benzene ring structure. The cashew phenol-modified polystyrene is uniformly dispersed in the polypropylene groups, which can improve its heat resistance and have a higher initial thermal decomposition temperature.

[0051] Comparative Example 2 added ordinary polystyrene, which does not contain alkyl long chains and cannot undergo physical chain entanglement with polypropylene, failing to form a tight physical cross-link. This did not increase the cross-linking density of the polypropylene molecular chains, resulting in a large water vapor permeability and poor barrier properties. Furthermore, polystyrene does not contain hydroxyl groups and cannot react with the compatibilizer maleic anhydride-grafted polypropylene, leading to poor compatibility between polystyrene and polypropylene. Consequently, the composite material exhibits poor mechanical properties, with low tensile and flexural strength.

[0052] Comparative Example 3 involved reacting aminated polystyrene with octadecyl glycidyl ether. Compared to cashew phenol glycidyl ether, octadecyl glycidyl ether does not contain a hydrophobic and heat-resistant benzene ring structure, resulting in a slightly higher water vapor permeability of the polypropylene composite material than in Example 1, and a lower initial thermal decomposition temperature than in Example 1.

[0053] Compared with Example 1, Comparative Example 4 did not add maleic anhydride-grafted polypropylene, resulting in lower compatibility between cashew phenol-modified polystyrene and polypropylene. This led to lower tensile and flexural strengths in the composite material, but higher than those in Comparative Example 1 and Comparative Example 2. This was mainly because the side chain of polystyrene introduced long alkyl chains of cashew phenol, which are similar to the molecular chain of polypropylene. The two have a certain degree of compatibility, which is beneficial to improving the mechanical strength of the material.

[0054] It is readily understood that the above embodiments are merely illustrative examples for clear explanation and do not imply that the invention is limited thereto. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom remain within the scope of protection of this 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 cashew phenol modified polystyrene, 1.2-2 parts by weight of maleic anhydride grafted polypropylene, and 0.15-0.3 parts by weight of antioxidant. The method for preparing cashew phenol-modified polystyrene is as follows: 100 parts by weight of amino-modified polystyrene are added to the reaction solvent, and after stirring, 8-25 parts by weight of cashew phenol glycidyl ether are added. After stirring and reacting, the solution is poured into ethanol, filtered, washed with ethanol, and dried to obtain cashew phenol-modified polystyrene. The reaction temperature is 45-60℃ and the reaction time is 12-18h. The preparation method of the aminated polystyrene is as follows: (1) Add polystyrene to chloroform, stir and then add a mixed acid solution of concentrated sulfuric acid and concentrated nitric acid. After the reaction, purify the solution, precipitate the precipitate, filter and dry to obtain nitrated polystyrene. The reaction temperature in step (1) is 30-40℃ and the reaction time is 3-6h. (2) Add stannous chloride to concentrated hydrochloric acid, stir and then add N,N-dimethylformamide solution of nitrated polystyrene dropwise. After the reaction, purify the solution, precipitate the precipitate, filter and dry to obtain amino polystyrene. The reaction temperature in step (2) is 90-100℃ and the reaction time is 12-18h.

2. The high-barrier polypropylene composite material according to claim 1, characterized in that, The antioxidant is a hindered phenolic 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. A method for preparing a high-barrier polypropylene composite material as described in any one of claims 1-3, characterized in that, The preparation method is as follows: polypropylene, cashew phenol modified polystyrene, maleic anhydride grafted polypropylene, and antioxidant are mixed, added to a twin-screw extruder, melt-extruded, and water-cooled and pelletized to obtain a high-barrier polypropylene composite material.

5. The method for preparing the high-barrier polypropylene composite material according to claim 4, characterized in that, The spindle speed of the twin-screw extruder is 100-200 r / min; the temperature in zones 1-6 is 170-215℃.