High-barrier polypropylene plastic cup and preparation method thereof

Abstract

The application discloses a kind of high barrier polypropylene plastic cups and preparation method thereof, it is related to high-performance polypropylene technical field.The method is to prepare silane pretreatment fluid with 3-methacryloxypropyl trimethoxysilane, after adding nano montmorillonite and reacting, drop into hexadecyl trimethyl ammonium bromide solution, after desolventizing, mixed with maleic anhydride grafted polypropylene, drying and crushing to obtain composite modified nano montmorillonite;Ethylene-vinyl alcohol copolymer is crosslinked with hexamethylene diisocyanate, then nano titanium dioxide modified by titanate coupling agent NDZ-311 is added, after reaction, precipitation, washing and drying, crosslinked modified EVOH is obtained;Polypropylene is mixed with composite modified nano montmorillonite, crosslinked modified EVOH, antioxidant 1010, antioxidant 168 and calcium stearate, extruded, pelletized and dried;The dried particles are injection molded into cup blanks, and the oven is cooled after heat preservation to obtain high barrier polypropylene plastic cups.The polypropylene plastic cup prepared by the application has excellent barrier properties.

Description

TECHNICAL FIELD

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

[0002] As a general thermoplastic resin, polypropylene (PP) has become the core raw material in the field of plastic cup preparation due to its low density, strong chemical corrosion resistance, balanced mechanical properties, and good processing fluidity. The polypropylene plastic cup made of this material is widely used in food packaging, daily beverage containers, and other fields. Not only is the raw material cost lower than that of engineering plastics such as polyethylene terephthalate (PET) and polyamide (PA), but it is also suitable for mass production. It also has mature injection molding and blow molding processes, can efficiently produce different specifications, and has good recyclability, which meets the development trend of environmentally friendly packaging.

[0003] However, the barrier performance of existing polypropylene plastic cups is insufficient, which has become a key technical bottleneck limiting their application range. From the specific defects, the polypropylene molecular chain has no strong polar group and a large intermolecular gap, which makes oxygen easily penetrate the cup and enter the interior. When used to hold oxidizable foods such as fruit juice and dairy products, it can accelerate the oxidation and deterioration of the contents, flavor deterioration, and nutrient loss, shortening the product shelf life. Secondly, it has insufficient barrier properties to carbon dioxide, and when used for carbonated beverages, the carbon dioxide in the cup easily leaks out, causing "gas loss" and affecting the taste of the beverage. In addition, the water vapor barrier is limited, and in high-humidity environments or when holding moisture-containing contents, water vapor easily penetrates the cup wall and migrates, causing moisture-absorbing solid foods such as nuts and baked goods to become soft, and the cup may also appear to be dewy and deformed. At the same time, it has poor barrier properties to food aroma components and external odors, which can not only cause the loss of characteristic aroma in the cup, but also easily allow external odors to penetrate, affecting food safety and experience.

[0004] The above-mentioned barrier performance defects make it difficult for traditional polypropylene plastic cups to meet the stringent requirements of high-end food and beverage packaging for barrier properties, so developing a polypropylene plastic cup with high barrier performance has become a technical problem that needs to be solved in the field. SUMMARY

[0005] The present application relates to the technical field of high-performance polypropylene plastic, in particular to a high-barrier polypropylene plastic cup and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0007] A preparation method of a high-barrier polypropylene plastic cup, comprising the following steps:

[0008] S1, 3-methacryloxypropyl trimethoxysilane is added to a mixture of anhydrous ethanol and deionized water, the pH is adjusted to be acidic, and stirring is performed to obtain a silane pretreatment solution; nano-montmorillonite is added to the silane pretreatment solution, ultrasonic dispersion is performed, and then stirring is performed to react, hexadecyl trimethyl ammonium bromide is dissolved in deionized water, and then the solution is added dropwise into the above reaction system and stirred to react, desolventization is performed, maleic anhydride grafted polypropylene is added and stirred to mix, and then drying, crushing and sieving are performed to obtain composite modified nano-montmorillonite;

[0009] S2, ethylene-vinyl alcohol copolymer is added into dimethyl sulfoxide and stirred to dissolve, hexamethylene diisocyanate and dibutyl tin dilaurate are added and stirred to crosslink, and then a crosslinking system is obtained; nano-titanium dioxide and titanate coupling agent NDZ-311 are added into dimethyl sulfoxide and ground and ultrasonic dispersed, and then the obtained mixture is added into the above crosslinking system, ultrasonic dispersion is performed, and then stirring is performed to react, deionized water is added dropwise after the reaction is completed to precipitate, and then the precipitate is washed with anhydrous ethanol, and drying, crushing and sieving are performed to obtain crosslinking modified EVOH;

[0010] S3, polypropylene, composite modified nano-montmorillonite, crosslinking modified EVOH, antioxidant 1010, antioxidant 168 and calcium stearate are added into a high-speed mixer and stirred to obtain a uniform mixture, the mixture is added into a double-screw extruder to be extruded, and then a water-cooled pelletizer is used to cut the particles, and then the particles are vacuum dried to obtain dry plastic particles;

[0011] S4, the dry plastic particles are added into an injection molding machine, the molten material is filled into a mold cavity, and then a polypropylene plastic cup blank is obtained after cooling and setting, the plastic cup blank is placed into a hot air drying oven for heat preservation, and then the oven is cooled to room temperature, and then a high-barrier polypropylene plastic cup is obtained.

[0012] In the technical scheme of the present application, the barrier properties of the polypropylene plastic cup are improved from two aspects: on the one hand, the original agglomeration state of the nano-montmorillonite is broken and the interlayer spacing is expanded by using silane pretreatment and hexadecyl trimethyl ammonium bromide intercalation treatment, and the affinity of the montmorillonite with the organic phase is also improved; then the interface bonding between the montmorillonite and the polypropylene matrix is further optimized by using maleic anhydride grafted polypropylene coating, so as to avoid the formation of voids between the two, and the modified nano-montmorillonite is uniformly distributed in the polypropylene matrix in a layered form, when small molecules such as oxygen and moisture attempt to penetrate the plastic cup, they need to move around multiple layers of montmorillonite, and the penetration path is greatly lengthened, which effectively hinders the direct penetration of small molecules; at the same time, the optimization of the interface bonding reduces the rapid penetration channels formed by the agglomeration of the montmorillonite or the interface voids, further strengthens the barrier effect on small molecules, and significantly reduces the penetration rate of oxygen and moisture.

[0013] On the other hand, the crosslinking treatment of the ethylene-vinyl alcohol copolymer using hexane diisocyanate converts the ethylene-vinyl alcohol copolymer from a linear molecular structure to a three-dimensional network structure, the structural compactness is significantly improved, and the pores that can be penetrated by small molecules are reduced; at the same time, the crosslinking structure can also inhibit the structural looseness of the ethylene-vinyl alcohol copolymer caused by moisture absorption, maintain its barrier stability, and avoid the penetration of small molecules through the pores after moisture absorption. At the same time, the nano-titanium dioxide modified by the titanate coupling agent is uniformly dispersed in the crosslinked ethylene-vinyl alcohol copolymer system, and the nano-titanium dioxide serves as a physical barrier point, further prolonging the penetration path of small molecules in the ethylene-vinyl alcohol copolymer. Small molecules need to bypass the nano-titanium dioxide particles to continue to diffuse, which is equivalent to adding an additional barrier on the basis of the dense structure of the ethylene-vinyl alcohol copolymer. In addition, the compatibility of the modified ethylene-vinyl alcohol copolymer with the polypropylene matrix is optimized, reducing the interface gap between the two, avoiding the rapid penetration of small molecules from the interface gap, and ultimately forming a further efficient barrier to oxygen and moisture.

[0014] The crosslinked modified ethylene-vinyl alcohol copolymer and the composite modified nano-montmorillonite form a dense crosslinked layer and a nano-sheet layer maze double barrier structure in the polypropylene matrix. Small molecules need to break through the dense crosslinked barrier of the ethylene-vinyl alcohol copolymer and the maze barrier of the montmorillonite in sequence, and finally the oxygen transmission rate and the moisture transmission rate of the plastic cup are significantly reduced.

[0015] As a preferred, in the step S1, the mass ratio of the nano-montmorillonite and the 3-methacryloyloxypropyl trimethoxysilane is 10:0.5-1.0.

[0016] As a preferred, in the step S1, the silane pretreatment liquid further adds glycidyl ether oxypropyl trimethoxysilane.

[0017] As a preferred, the mass ratio of the nano-montmorillonite and the glycidyl ether oxypropyl trimethoxysilane is 10:0.3-0.6.

[0018] In the technical scheme of the present application, the research and development team found through in-depth research that the composite modified nano-montmorillonite (inorganic phase) and the cross-linked modified ethylene-vinyl alcohol copolymer (organic phase) are used to improve the barrier property of the polypropylene plastic cup. Although the compatibility of the two with the polypropylene (PP) matrix has been optimized, there is a lack of strong interaction between the two, and micro voids are easily formed at the interface, which will become a channel for small molecules such as oxygen and water molecules to penetrate, thereby weakening the barrier effect of the synergistic effect of the two. To further solve this technical problem, the invention team adds a specified amount of glycidyl ether oxypropyl trimethoxysilane to the silane pretreatment liquid, which generates a bifunctional molecule containing epoxy and silicon hydroxyl groups after hydrolysis. The silicon hydroxyl group can undergo dehydration condensation reaction with the hydroxyl group on the surface of the nano-montmorillonite, and the epoxy group is firmly grafted onto the surface of the montmorillonite. The grafted epoxy group can undergo ring-opening reaction with the hydroxyl group in the cross-linked modified ethylene-vinyl alcohol copolymer molecule in the subsequent processing process to form a covalent bond, thereby building a stable chemical bond bridge between the two, eliminating the interface micro voids, and further improving the barrier effect of oxygen and water vapor.

[0019] Preferably, in step S1, the mass ratio of nano-montmorillonite to cetyltrimethylammonium bromide is 25:8-12.

[0020] Preferably, in step S2, the mass ratio of ethylene-vinyl alcohol copolymer to hexamethylene diisocyanate is 1:2-3.

[0021] Preferably, in step S2, the mass ratio of nano-titanium dioxide to titanium ester coupling agent NDZ-311 is 10:0.2-0.5.

[0022] Preferably, in step S3, the mass ratio of polypropylene, composite modified nano-montmorillonite, and cross-linked modified EVOH is 950:20-25:40-60.

[0023] Preferably, in step S3, the mass ratio of antioxidant 1010 to antioxidant 168 is 1:2-3.

[0024] A high-barrier polypropylene plastic cup is prepared by the method described above.

[0025] Compared with the prior art, the present application has the following advantages:

[0026] 1. The composite modified nano-montmorillonite forms a labyrinth effect in the polypropylene matrix, combined with the three-dimensional dense structure of the cross-linked modified EVOH and the physical barrier points of the nano-titanium dioxide, forming a double barrier structure of the labyrinth barrier and the dense cross-linked barrier, so that small molecules need to break through two barriers in turn, and finally the oxygen transmission rate and the moisture transmission rate of the plastic cup are greatly reduced.

[0027] 2. By adding glycidyl etheroxypropyltrimethoxysilane during the pretreatment stage of nano-montmorillonite silane, the epoxy groups grafted after hydrolysis can form covalent bonds with the hydroxyl groups of cross-linked modified EVOH, constructing a stable chemical bond bridge, eliminating the interfacial micropores between the inorganic and organic modified phases in the original system, blocking the small molecule permeation channels, further strengthening the synergistic effect of the two, and avoiding the weakening of the barrier performance due to interfacial defects. Attached Figure Description

[0028] Figure 1 This is a cross-sectional SEM image of the high-barrier polypropylene plastic cup prepared according to the present invention. Detailed Implementation

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0030] Example 1

[0031] A method for preparing a high-barrier polypropylene plastic cup includes the following steps:

[0032] Step 1: Weigh 2.20g of 3-methacryloxypropyltrimethoxysilane and 1.25g of glycidyl etheroxypropyltrimethoxysilane, add them to a mixture containing 360mL of anhydrous ethanol and 90mL of deionized water, adjust the pH to 4.2 by adding glacial acetic acid dropwise, place in a 32℃ constant temperature water bath and stir at 300rpm for 40min to obtain silane pretreatment solution;

[0033] 25g of nano-montmorillonite was added to the silane pretreatment solution and dispersed by ultrasonication at 350W for 25min. The solution was then transferred to a 65℃ water bath and stirred at 320rpm for 1.8h. 11g of hexadecyltrimethylammonium bromide was dissolved in 240mL of deionized water and added dropwise to the above reaction system at 1.5mL / min. The mixture was stirred at 280rpm and heated to 80℃ for 3.5h. The reaction system was then placed under 80℃ and -0.095MPa vacuum for 2h to remove the solvent, followed by further heating to 90℃ for 1h to remove the solvent. 5g of maleic anhydride-grafted polypropylene was added and the mixture was heated to 155℃ and stirred at 1100rpm for 45min. The mixture was dried under 85℃ and -0.095MPa vacuum for 5h, pulverized, and passed through a 200-mesh sieve to obtain composite modified nano-montmorillonite.

[0034] Step 2: 34 g of ethylene-vinyl alcohol copolymer was weighed into 300 mL of dimethyl sulfoxide and placed in a 90℃ constant temperature water bath for stirring at 220 rpm for 40 min until completely dissolved; 95 g of hexamethylene diisocyanate and 0.21 g of dibutyltin dilaurate were added to the solution, and the temperature was lowered to 75℃ for crosslinking at 180 rpm for 2.2 h to obtain a crosslinked system;

[0035] 1.07 g of nano-titanium dioxide and 0.04 g of titanium acid ester coupling agent NDZ-311 were weighed into 10 mL of dimethyl sulfoxide and ground for 10 min, and then dispersed by ultrasonic for 5 min at 450 W. The obtained mixture was added to the above crosslinked system, and then ultrasonic dispersion was continued for 30 min at 450 W. After that, the system was placed in a 75℃ water bath for stirring at 200 rpm for 1 h. After the reaction was completed, the system was dropped into deionized water at a rate of 4 mL / min to precipitate the sediment. The sediment was washed with anhydrous ethanol for 4 times, and then dried in a vacuum oven at 80℃ and -0.095 MPa for 4 h. After being crushed and sieved through a 180 mesh sieve, a crosslinked and modified ethylene-vinyl alcohol copolymer was obtained.

[0036] Step 3: 950 g of polypropylene, 24 g of composite modified nano-montmorillonite, 55 g of crosslinked and modified ethylene-vinyl alcohol copolymer, 0.67 g of antioxidant 1010, 1.90 g of antioxidant 168, and 1 g of calcium stearate were weighed into a high-speed mixer, and a uniform mixture was obtained by setting the temperature to 135℃ and the rotation speed to 900 rpm for 12 min. The mixture was then added to a twin-screw extruder, and the temperature of each zone was set to 170℃, 185℃, 195℃, 200℃, and 200℃, respectively. The screw rotation speed was set to 220 rpm, and the residence time of the material was set to 2 min. After the material was stably extruded, it was cut into particles with a length of 2-3 mm by a water-cooled pelletizer. The particles were then dried in a vacuum oven at 85℃ and -0.095 MPa to obtain dry plastic particles.

[0037] Step 4: The dry plastic particles were added to the hopper of an injection molding machine, and the barrel temperature was set to 195℃, 205℃, 215℃, and 225℃ for the first, second, third, and fourth zones, respectively. The mold temperature was set to 50℃, the injection pressure was set to 70 MPa, the holding pressure was set to 45 MPa, the injection time was set to 12 s, the holding time was set to 8 s, and the cooling time was set to 25 s. After the barrel temperature was stable for 10 min, the injection was started, and the molten material filled the mold cavity. After cooling and setting, the polypropylene plastic cup blank was taken out of the mold. The plastic cup blank was placed in a forced air drying oven, the temperature was set to 95℃, and the temperature was maintained for 1.5 h. Then the heating was turned off, and the oven was cooled to room temperature. A high-barrier polypropylene plastic cup was obtained.

[0038] Example 2

[0039] A method for preparing a high-barrier polypropylene plastic cup, comprising the following steps:

[0040] Step 1: 1.65 g of 3-methacryloxypropyltrimethoxysilane and 0.90 g of glycidyl ether oxypropyltrimethoxysilane were weighed and added to a mixture of 360 mL of anhydrous ethanol and 90 mL of deionized water, and 1.65 g of 3-methacryloxypropyltrimethoxysilane and 0.90 g of glycidyl ether oxypropyltrimethoxysilane were added dropwise to adjust the pH to 4.2, and the mixture was stirred at 300 rpm in a 32°C constant temperature water bath for 40 min to obtain a silane pretreatment solution;

[0041] 25 g of nanometer-sized montmorillonite was added to the silane pretreatment solution, and dispersed by ultrasonic at 350 W for 25 min, and then transferred to a 65°C water bath and stirred at 320 rpm for 1.8 h. 9 g of cetyltrimethylammonium bromide was dissolved in 240 mL of deionized water, and then added dropwise to the above reaction system at a rate of 1.5 mL / min, and the stirring was maintained at 280 rpm and the temperature was raised to 80°C, and the reaction was continued for 3.5 h. The reaction system was placed in a vacuum oven at 80°C and -0.095 MPa for 2 h, and then the temperature was raised to 90°C and the reaction was continued for 1 h. 5 g of maleic anhydride grafted polypropylene was added, and the mixture was stirred at 1100 rpm and the temperature was raised to 155°C for 45 min. The mixture was dried in a vacuum oven at 85°C and -0.095 MPa for 5 h, and then crushed and sieved through a 200 mesh sieve to obtain the composite modified nanometer-sized montmorillonite.

[0042] Step 2: 34 g of ethylene-vinyl alcohol copolymer was weighed and added to 300 mL of dimethyl sulfoxide, and then placed in a 90°C constant temperature water bath and stirred at 220 rpm for 40 min until completely dissolved. 80 g of hexamethylene diisocyanate and 0.21 g of dibutyltin dilaurate were added to the solution, and then the temperature was lowered to 75°C and the stirring was maintained at 180 rpm for 2.2 h to obtain a crosslinked system.

[0043] 1.07 g of nanometer-sized titanium dioxide and 0.03 g of titanium ester coupling agent NDZ-311 were weighed and added to 10 mL of dimethyl sulfoxide and ground for 10 min, and then dispersed by ultrasonic at 450 W for 5 min. The obtained mixture was added to the above crosslinked system, and then dispersed by ultrasonic at 450 W for 30 min, and then placed in a 75°C water bath and stirred at 200 rpm for 1 h. After the reaction was completed, the system was added dropwise to deionized water at a rate of 4 mL / min to precipitate the product, which was washed with anhydrous ethanol 4 times, and then dried in a vacuum oven at 80°C and -0.095 MPa for 4 h, and then crushed and sieved through a 180 mesh sieve to obtain the crosslinked modified ethylene-vinyl alcohol copolymer.

[0044] Step 3: 950 g of polypropylene, 22 g of composite modified nanometer montmorillonite, 45 g of crosslinking modified ethylene-vinyl alcohol copolymer, 0.67 g of antioxidant 1010, 1.50 g of antioxidant 168 and 1 g of calcium stearate were weighed and added to a high-speed mixer, the temperature was set to 135°C and the rotation speed was set to 900 rpm, and stirring was performed for 12 min to obtain a uniform mixture; the mixture was added to a twin-screw extruder, and the temperature of each zone was set to 170°C, 185°C, 195°C, 200°C and 200°C, the screw rotation speed was 220 rpm, the residence time of the material was 2 min, and after the material was stably extruded, it was cut into particles with a length of 2-3 mm by a water-cooled pelletizer; the particles were dried in a vacuum oven at 85°C and -0.095 MPa to obtain dry plastic particles.

[0045] Step 4: The dry plastic particles were added to the hopper of an injection molding machine, and the barrel temperature was set to 195°C, 205°C, 215°C and 225°C, the mold temperature was 50°C, the injection pressure was 70 MPa, the holding pressure was 45 MPa, the injection time was 12 s, the holding time was 8 s, and the cooling time was 25 s; after the barrel temperature was stable for 10 min, the injection was started, the molten material filled the mold cavity, and after cooling and shaping, the polypropylene plastic cup blank was taken out; the plastic cup blank was placed in a forced air drying oven, the temperature was set to 95°C, and the temperature was maintained for 1.5 h, then the heating was turned off, and the oven was cooled to room temperature, to obtain a high-barrier polypropylene plastic cup.

[0046] Example 3

[0047] A method for preparing a high-barrier polypropylene plastic cup, comprising the following steps:

[0048] Step 1: 2.0 g of 3-methacryloyloxypropyltrimethoxysilane and 1.0 g of glycidyl ether oxypropyltrimethoxysilane were added to a mixture of 360 mL of anhydrous ethanol and 90 mL of deionized water, and ice acetic acid was added dropwise to adjust the pH to 4.2, and then the mixture was placed in a 32°C constant temperature water bath and stirred at 300 rpm for 40 min to obtain a silane pretreatment solution;

[0049] Into the silane pretreatment solution, 25 g of nanometer montmorillonite was added, and dispersed by ultrasonic at 350 W for 25 min, then transferred to a 65 °C water bath to react for 1.8 h with stirring at 320 rpm. 10 g of hexadecyl trimethyl ammonium bromide was dissolved in 240 mL of deionized water, and added dropwise into the above reaction system at a rate of 1.5 mL / min, while keeping the stirring at 280 rpm and the temperature at 80 °C, and then reacted for another 3.5 h. The reaction system was placed in a vacuum condition of 80 °C and -0.095 MPa to desolventize for 2 h, and then heated to 90 °C to desolventize for 1 h. 5 g of maleic anhydride grafted polypropylene was added, and the mixture was heated to 155 °C and stirred at 1100 rpm for 45 min. The mixture was dried at 85 °C and -0.095 MPa vacuum for 5 h, crushed and sieved through a 200 mesh sieve to obtain the composite modified nanometer montmorillonite.

[0050] Step 2: 34 g of ethylene-vinyl alcohol copolymer was weighed into 300 mL of dimethyl sulfoxide, and placed in a 90 °C constant temperature water bath to stir at 220 rpm for 40 min until completely dissolved. 90 g of hexamethylene diisocyanate and 0.21 g of dibutyl tin dilaurate were added to the solution, and the temperature was lowered to 75 °C to crosslink at 180 rpm for 2.2 h to obtain a crosslinked system.

[0051] 1.07 g of nanometer titanium dioxide and 0.035 g of titanate coupling agent NDZ-311 were weighed into 10 mL of dimethyl sulfoxide and ground for 10 min, and then dispersed by ultrasonic at 450 W for 5 min. The obtained mixture was added to the above crosslinked system, and then dispersed by ultrasonic at 450 W for another 30 min. After that, the system was placed in a 75 °C water bath to react for 1 h with stirring at 200 rpm. After the reaction was completed, the system was added dropwise into deionized water at a rate of 4 mL / min to precipitate the sediment, which was washed with anhydrous ethanol for 4 times, dried at 80 °C and -0.095 MPa vacuum for 4 h, crushed and sieved through a 180 mesh sieve to obtain the crosslinked modified ethylene-vinyl alcohol copolymer.

[0052] Step 3: 950 g of polypropylene, 23 g of composite modified nanometer montmorillonite, 50 g of crosslinked modified ethylene-vinyl alcohol copolymer, 0.67 g of antioxidant 1010, 1.75 g of antioxidant 168 and 1 g of calcium stearate were weighed into a high-speed mixer, and set to a temperature of 135 °C and a rotation speed of 900 rpm to stir for 12 min to obtain a uniform mixture. The mixture was added to a twin-screw extruder, and the temperature of each zone was set to 170 °C for the first zone, 185 °C for the second zone, 195 °C for the third zone, 200 °C for the fourth zone, and 200 °C for the die head. The screw rotation speed was set to 220 rpm, and the residence time of the material was set to 2 min. After the material was stably extruded, it was cut into particles with a length of 2-3 mm by a water-cooled pelletizer. The particles were dried at 85 °C and -0.095 MPa vacuum to obtain dry plastic particles.

[0053] Step 4: Dry plastic particles are added to the injection molding machine hopper, and the barrel temperature is set: Zone 1 195℃, Zone 2 205℃, Zone 3 215℃, Zone 4 225℃, mold temperature 50℃, injection pressure 70MPa, holding pressure 45MPa, injection time 12s, holding time 8s, cooling time 25s; after the barrel temperature is stable for 10min, start injection molding, melt material fills the mold cavity, and after cooling and setting, the polypropylene plastic cup blank is taken out; the plastic cup blank is placed in a forced air drying oven, the temperature is set to 95℃, and the temperature is maintained for 1.5h, then the heating is turned off, and the oven is cooled to room temperature, obtaining a high-barrier polypropylene plastic cup.

[0054] Example 4

[0055] A method for preparing a high-barrier polypropylene plastic cup, comprising the following steps:

[0056] Step 1: Weigh 2.50g 3-methacryloxypropyltrimethoxysilane and 1.50g glycidyl ether oxypropyltrimethoxysilane into a mixture of 360mL anhydrous ethanol and 90mL deionized water, add glacial acetic acid to adjust the pH to 4.2, and stir at 300rpm in a 32℃ constant temperature water bath for 40min to obtain a silane pretreatment solution;

[0057] Add 25g of nano-montmorillonite to the silane pretreatment solution, disperse for 25min under 350W ultrasonic, then transfer to a 65℃ water bath and stir at 320rpm for 1.8h, dissolve 12g of cetyltrimethylammonium bromide in 240mL of deionized water, and add it to the above reaction system at a rate of 1.5mL / min, while maintaining stirring at 280rpm and heating to 80℃, continue to react for 3.5h; place the reaction system in a vacuum of -0.095MPa at 80℃ for 2h, then heat to 90℃ for 1h, add 5g of maleic anhydride grafted polypropylene, heat to 155℃ and stir at 1100rpm for 45min, dry the mixture in a vacuum oven at 85℃ and -0.095MPa for 5h, crush and pass through a 200 mesh sieve to obtain a composite modified nano-montmorillonite.

[0058] Step 2: Weigh 34g of ethylene-vinyl alcohol copolymer into 300mL of dimethyl sulfoxide, and stir at 220rpm in a 90℃ constant temperature water bath for 40min until completely dissolved; add 102g of hexamethylene diisocyanate and 0.21g of dibutyltin dilaurate to the solution, cool to 75℃, and stir at 180rpm for 2.2h to obtain a crosslinked system;

[0059] Take 1.07 g of nano-titanium dioxide and 0.05 g of titanate coupling agent NDZ-311, add 10 mL of dimethyl sulfoxide and grind for 10 min, ultrasonic dispersion for 5 min, then add the mixture to the above crosslinking system, continue to ultrasonic dispersion for 30 min, then place in a 75℃ water bath and stir at 200 rpm for 1 h; after the reaction is completed, the system is dropped into deionized water at a rate of 4 mL / min to precipitate the sediment, washed with anhydrous ethanol 4 times, vacuum dried at 80℃, -0.095 MPa for 4 h, crushed and sieved through a 180 mesh sieve to obtain a crosslinked modified ethylene-vinyl alcohol copolymer.

[0060] Step 3: Take 950 g of polypropylene, 25 g of composite modified nano-montmorillonite, 60 g of crosslinked modified ethylene-vinyl alcohol copolymer, 0.67 g of antioxidant 1010, 2.01 g of antioxidant 168 and 1 g of calcium stearate, and add them to a high-speed mixer, set the temperature to 135℃ and the rotation speed to 900 rpm, and stir for 12 min to obtain a uniform mixture; add the mixture to a twin-screw extruder, set the temperature of each zone to 170℃, 185℃, 195℃, 200℃ and 200℃, respectively, and the screw rotation speed to 220 rpm, and the material residence time to 2 min; after the material is stably extruded, cut it into 2-3 mm long particles using a water-cooled pelletizer; and dry the particles in a vacuum oven at 85℃, -0.095 MPa to obtain dry plastic particles.

[0061] Step 4: Add the dry plastic particles to the hopper of an injection molding machine, set the barrel temperature to 195℃, 205℃, 215℃ and 225℃, respectively, the mold temperature to 50℃, the injection pressure to 70 MPa, the holding pressure to 45 MPa, the injection time to 12 s, the holding time to 8 s and the cooling time to 25 s; after the barrel temperature is stable for 10 min, start the injection, fill the mold cavity with the molten material, and after cooling and setting, open the mold to take out the polypropylene plastic cup blank; place the plastic cup blank in a forced air drying oven, set the temperature to 95℃, and keep it for 1.5 h, then turn off the heating and cool it to room temperature, to obtain a high-barrier polypropylene plastic cup.

[0062] Example 5

[0063] A method for preparing a high-barrier polypropylene plastic cup, comprising the following steps:

[0064] Step 1: Take 1.25 g of 3-methacryloyloxypropyltrimethoxysilane and 0.75 g of glycidyl ether oxypropyltrimethoxysilane, add them to a mixture of 360 mL of anhydrous ethanol and 90 mL of deionized water, drop in glacial acetic acid to adjust the pH to 4.2, place in a 32℃ constant temperature water bath for 40 min at 300 rpm to obtain a silane pretreatment solution;

[0065] Into the silane pretreatment solution, 25 g of nanometer montmorillonite was added, and dispersed by ultrasonic at 350 W for 25 min, then transferred to a 65℃ water bath to react for 1.8 h with stirring at 320 rpm. 8 g of hexadecyl trimethyl ammonium bromide was dissolved in 240 mL of deionized water, and added dropwise into the above reaction system at a rate of 1.5 mL / min, while keeping stirring at 280 rpm and heating to 80℃, and then continued to react for 3.5 h. The reaction system was placed in a vacuum condition of 80℃ and -0.095 MPa for 2 h to desolventize, and then heated to 90℃ for 1 h to desolventize. 5 g of maleic anhydride grafted polypropylene was added, and the mixture was heated to 155℃ and stirred at 1100 rpm for 45 min. The mixture was dried at 85℃ and -0.095 MPa vacuum for 5 h, crushed and sieved through a 200 mesh screen to obtain the composite modified nanometer montmorillonite.

[0066] Step 2: 34 g of ethylene-vinyl alcohol copolymer was weighed into 300 mL of dimethyl sulfoxide, and placed in a 90℃ constant temperature water bath to stir at 220 rpm for 40 min until completely dissolved. 68 g of hexamethylene diisocyanate and 0.21 g of dibutyl tin dilaurate were added to the solution, and the temperature was lowered to 75℃ to crosslink at 180 rpm for 2.2 h to obtain a crosslinked system.

[0067] 1.07 g of nanometer titanium dioxide and 0.02 g of titanate coupling agent NDZ-311 were weighed into 10 mL of dimethyl sulfoxide and ground for 10 min, and then dispersed by ultrasonic at 450 W for 5 min. The obtained mixture was added to the above crosslinked system, and then dispersed by ultrasonic at 450 W for 30 min. After that, the system was placed in a 75℃ water bath to react for 1 h with stirring at 200 rpm. After the reaction was completed, the system was added dropwise into deionized water at a rate of 4 mL / min to precipitate the sediment, which was washed with anhydrous ethanol for 4 times, dried at 80℃ and -0.095 MPa vacuum for 4 h, crushed and sieved through a 180 mesh screen to obtain the crosslinked modified ethylene-vinyl alcohol copolymer.

[0068] Step 3: 950 g of polypropylene, 20 g of composite modified nanometer montmorillonite, 40 g of crosslinked modified ethylene-vinyl alcohol copolymer, 0.67 g of antioxidant 1010, 1.34 g of antioxidant 168 and 1 g of calcium stearate were weighed into a high-speed mixer, and set to a temperature of 135℃ and a rotation speed of 900 rpm to stir for 12 min to obtain a uniform mixture. The mixture was added to a twin-screw extruder, and the temperature of each zone was set to 170℃ for the first zone, 185℃ for the second zone, 195℃ for the third zone, 200℃ for the fourth zone and 200℃ for the die head. The screw rotation speed was set to 220 rpm, and the residence time of the material was set to 2 min. After the material was stably extruded, it was cut into particles with a length of 2-3 mm by a water-cooled pelletizer. The particles were dried under vacuum at 85℃ and -0.095 MPa to obtain dry plastic particles.

[0069] Step 4: The dry plastic particles were added to the hopper of the injection molding machine, and the barrel temperature was set: Zone 1 195℃, Zone 2 205℃, Zone 3 215℃, Zone 4 225℃, mold temperature 50℃, injection pressure 70MPa, holding pressure 45MPa, injection time 12s, holding time 8s, cooling time 25s; after the barrel temperature was stable for 10min, the injection was started, the molten material filled the mold cavity, and after cooling and setting, the polypropylene plastic cup blank was taken out; the plastic cup blank was placed in a forced air drying oven, the temperature was set to 95℃, and the temperature was maintained for 1.5h, then the heating was turned off, and the oven was cooled to room temperature, obtaining a high-barrier polypropylene plastic cup.

[0070] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that Step 1 is omitted in the preparation process of the polypropylene plastic cup, and the composite modified nanometer montmorillonite in Step 3 is replaced by equal mass of montmorillonite.

[0071] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that Step 2 is omitted in the preparation process of the polypropylene plastic cup, and the cross-linked modified ethylene-vinyl alcohol copolymer in Step 3 is replaced by equal mass of ethylene-vinyl alcohol copolymer.

[0072] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that glycidyl ether propyltrimethoxysilane is not added in Step 1 in the preparation process of the polypropylene plastic cup.

[0073] Performance test:

[0074] 1. Oxygen transmission rate test: according to GB / T 31354-2014, take 3 parallel samples of each of Examples 1-5 and Comparative Examples 1-3, rinse and dry, and then equilibrate at 23℃, 50%RH for 24h; seal and fix a single cup to a coulometric tester, pass 99.99% oxygen (0.1MPa±0.005MPa, 10mL / min±1mL / min) into the cup, pass nitrogen containing 5% hydrogen (20mL / min±1mL / min) outside the cup, set 23℃±0.5℃, 50%±2%RH, and test for 24h after the baseline is stable; oxygen transmits through the cup (effective area 0.012m 2 ) and reacts with the carrier gas, and the sensor records the current, first calculates the oxygen transmission rate per unit area, and then multiplies 0.012m 2 to get the oxygen transmission rate of a single cup, and take the average of 3 parallel samples. The test results are shown in Table 1.

[0075] 2. Moisture permeability test: According to GB / T 1037-2021 "Determination of water vapour transmission rate of plastics films and sheets-gravimetric method", take 3 parallel samples of each of Examples 1-5 and Comparative Examples 1-3, rinse and dry, then equilibrate at 23℃, 50% RH for 24h, place the individual cups upside down and sealed on the moisture permeable cup containing anhydrous calcium chloride (drying agent), set the test temperature to 38℃±0.5℃ and relative humidity to 90%±2%, weigh the total mass of the moisture permeable cup every 6h for 24h, directly calculate the moisture permeability of the individual cup, and take the average of 3 parallel samples. The test results are shown in Table 1.

[0076] 3. Heat distortion temperature test: According to the national standard GB / T 1633-2000 "Determination of Vicat softening temperature (VST) and heat distortion temperature (HDT) of thermoplastics", cut each sample into a standard sample of 120mm x 10mm x 4mm (take 3 parallel samples for each sample), use a heat distortion temperature tester, set the test load to 1.82MPa and the temperature rise rate to 120℃ / h, record the temperature at which the sample bends and deforms by 0.25mm, take the average of 3 parallel samples as the heat distortion temperature, in units of ℃, to verify the heat resistance and stability of the product. The test results are shown in Table 1.

[0077] Table 1:

[0078] oxygen transmission rate (cm 3 / (pkg 24h) Moisture permeability (g / (pkg 24h)) Heat distortion temperature (°C) Example 1 0.0058 0.0043 113 Example 2 0.0076 0.0056 110 Example 3 0.0063 0.0049 112 Example 4 0.0052 0.0038 115 Example 5 0.0083 0.0062 109 Comparative Example 1 0.0285 0.0184 106 Comparative Example 2 0.0253 0.0158 107 Comparative Example 3 0.0126 0.0097 109

[0079] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments, or make equivalent replacements to some of the technical features, as long as they are within the spirit and principles of the present application. Any modifications, equivalent replacements, improvements, etc. made within the scope of the present application should be included in the protection scope of the present application.

Claims

1. A process for the preparation of high barrier polypropylene plastic cups, characterized in that, It comprises the following steps: S1, 3-methacryloxypropyl trimethoxysilane and glycidyl ether oxygen propyl trimethoxysilane are added to a mixture of anhydrous ethanol and deionized water, the pH is adjusted to be acidic, and stirring is performed to obtain a silane pretreatment solution; nano montmorillonite is added to the silane pretreatment solution, ultrasonic dispersion is performed, and then stirring is performed to react; cetyl trimethyl ammonium bromide is dissolved in deionized water, and then it is added dropwise into the above reaction system and stirred to react; desolventization is performed; maleic anhydride grafted polypropylene is added, and then the temperature is increased to 155 DEG C and stirring is performed to mix; after drying and crushing, a composite modified nano montmorillonite is obtained; S2, ethylene-vinyl alcohol copolymer is added to dimethyl sulfoxide and stirred to dissolve; hexamethylene diisocyanate and dibutyl tin dilaurate are added and stirred to crosslink, so as to obtain a crosslinking system; nano titanium dioxide and titanate coupling agent NDZ-311 are added to dimethyl sulfoxide and ground and ultrasonic dispersed; the obtained mixture is added to the above crosslinking system, ultrasonic dispersed, and then stirred to react; after the reaction is completed, deionized water is added dropwise to precipitate, washed with anhydrous ethanol, dried, crushed, and sieved, so as to obtain crosslinking modified EVOH; S3, polypropylene, composite modified nano montmorillonite, crosslinking modified EVOH, antioxidant 1010, antioxidant 168, and calcium stearate are added to a high-speed mixer and stirred to obtain a uniform mixture; the mixture is added to a double-screw extruder and extruded; the extrudate is cut by a water-cooled pelletizer, and the pellets are vacuum dried, so as to obtain dry plastic particles; S4, the dry plastic particles are added to an injection molding machine, the molten material is filled into a mold cavity, and after cooling and setting, a polypropylene plastic cup blank is obtained; the plastic cup blank is placed in a hot air drying oven for heat preservation, and then cooled to room temperature with the oven, so as to obtain a high-barrier polypropylene plastic cup.

2. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, In the step S1, the mass ratio of the nano montmorillonite to the 3-methacryloxypropyl trimethoxysilane is 10:0.5-1.

0.

3. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, The mass ratio of the nano montmorillonite to the glycidyl ether oxygen propyl trimethoxysilane is 10:0.3-0.

6.

4. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, In the step S1, the mass ratio of the nano montmorillonite to the cetyl trimethyl ammonium bromide is 25:8-12.

5. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, In the step S2, the mass ratio of the ethylene-vinyl alcohol copolymer to the hexamethylene diisocyanate is 1:2-3.

6. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, In the step S2, the mass ratio of the nano titanium dioxide to the titanate coupling agent NDZ-311 is 10:0.2-0.

5.

7. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, In the step S3, the mass ratio of the polypropylene, the composite modified nano montmorillonite, and the crosslinking modified EVOH is 950:20-25:40-60.

8. The method for preparing a high-barrier polypropylene plastic cup according to claim 1, characterized in that, In the step S3, the mass ratio of the antioxidant 1010 to the antioxidant 168 is 1:2-3.

9. A high barrier polypropylene plastic cup characterized in that, Prepared by the method of any one of the above claims 1-8. In the step S1, the mass ratio of the nano montmorillonite to the 3-methacryloxypropyl trimethoxysilane is 10:0.5-1.

0. The mass ratio of the nano montmorillonite to the glycidyl ether oxygen propyl trimethoxysilane is 10:0.3-0.

6. In the step S1, the mass ratio of the nano montmorillonite to the cetyl trimethyl ammonium bromide is 25:8-12. In the step S2, the mass ratio of the ethylene-vinyl alcohol copolymer to the hexamethylene diisocyanate is 1:2-3. In the step S2, the mass ratio of the nano titanium dioxide to the titanate coupling agent NDZ-311 is 10:0.2-0.

5. In the step S3, the mass ratio of the polypropylene, the composite modified nano montmorillonite, and the crosslinking modified EVOH is 950:20-25:40-60. In the step S3, the mass ratio of the antioxidant 1010 to the antioxidant 168 is 1:2-3. Prepared by the method of any one of the above claims 1-8.

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