Preparation method and manufacturing process of corn packaging vacuum bag

Abstract

The invention discloses a preparation method and a manufacturing process of a corn packaging vacuum bag, and relates to the technical field of vacuum bags, the corn packaging vacuum bag is prepared from the following components in parts by weight: 30-70 parts of polypropylene, 30-70 parts of polyethylene, 5-20 parts of vinyl elastomer, 5-10 parts of allyl elastomer, 5-20 parts of polyolefin elastomer, 10-20 parts of SEBS and 1-10 parts of stabilizer. The compatilizer contains self-made maleic anhydride grafted SEBS, the maleic anhydride grafted SEBS with the highest grafting rate is selected as a raw material to be added, so that the compatibility between the SEBS and other raw materials is improved, the characteristics of the SEBS are fully integrated into a vacuum bag, the materials are more fully mixed through other components of the compatilizer, and the mechanical properties of the vacuum bag are improved. The final vacuum bag has wider temperature tolerance upper and lower limits, the toughness of the vacuum bag is improved, the bag breaking rate is remarkably reduced, meanwhile, the adsorbent is added in the manufacturing process, the content of volatile organic compounds in the vacuum bag is remarkably reduced, and potential threats to health are reduced.

Description

Technical Field

[0001] The invention relates to the technical field of vacuum bags, and in particular to a preparation method and a manufacturing process of a vacuum bag for corn packaging. Background Art

[0002] Corn is one of the main food crops in my country, and its output and planting area are both among the highest. According to data from China Report Hall, corn accounts for nearly 40% of China's total grain output and is China's largest crop. Corn has a wide range of uses in China, of which more than 60% is used as feed, and is the link between the planting and breeding industries. Corn is also an important industrial raw material for the production of starch, alcohol, sugar and other products. Deep processing consumption is expected to increase. Corn is also one of the important food sources for Chinese people. Although direct consumption accounts for a small proportion, corn is an important staple or complementary food in some regions or specific populations. China's corn harvested area ranks first in the world all year round, and its output is second only to the United States, making it the world's second largest corn producer.

[0003] Vacuum bag packaging of corn is a common corn processing method in the modern food industry, which has many advantages. 1. Vacuum packaging can effectively extend the shelf life of corn and prevent the growth of bacteria and mold, thereby maintaining the freshness and taste of corn; 2. Vacuum bag packaging of corn is small in size, light in weight, and easy to carry and store. Whether it is an outdoor picnic, travel or daily consumption, it is very convenient; 3. Under the protection of vacuum packaging, the color, taste and nutritional value of corn can be maintained for a long time. Even after a long period of storage and transportation, after opening the vacuum packaging, you can still smell the tempting corn fragrance and the taste is still delicious.

[0004] At present, many foods are stored in vacuum bags. By removing the air in the vacuum bags, especially oxygen, the growth and reproduction of most microorganisms such as molds and yeasts can be significantly inhibited. These microorganisms are one of the main factors leading to food spoilage. At the same time, fat, protein and other components in food are easily affected by oxygen and undergo oxidation reactions, causing food spoilage. Vacuum packaging can effectively isolate the air and prevent food oxidation, thereby extending the shelf life of food. In addition, vacuum packaging isolates food from the external environment, avoids the cross-odor of food or between food and air, and maintains the original flavor of the food.

[0005] During the vacuuming process, the gas in the vacuum bag is extracted and the vacuum bag will be subjected to external pressure. If the material strength of the vacuum bag is insufficient or there are defects, the vacuum bag may rupture at these places. The ruptured vacuum bag cannot continue to protect the food and may cause the food to be contaminated or deteriorate. The deformation may also affect the appearance and quality of the food, giving consumers a bad impression of it.

[0006] The plastic film used for vacuum bags usually contains chemicals such as polyethylene and polyvinyl chloride. These substances are common components of plastics and have characteristics such as water resistance and chemical corrosion resistance. Therefore, they are widely used in the packaging industry. However, these substances may penetrate into food during long-term contact with food, especially in a hot and humid environment. If the chemicals in the vacuum bag migrate into the food and the migration amount exceeds the safety standard, it will pose a potential threat to the health of consumers. And polyethylene (PE), as one of the main raw materials for vacuum bag plastic film, has excellent low-temperature resistance, and the lowest use temperature can reach -100~-70 °C. At the same time, it also has the characteristics of good chemical stability, low water absorption, and excellent electrical insulation, but the strength is general, it is easily affected by stress cracking, and the resistance to ultraviolet rays and heat resistance is poor. Polypropylene (PP) material has a temperature range of -20~120℃ and has strong heat resistance. There is a complementary disadvantage between polyethylene and polypropylene materials. When the two are mixed as raw materials, some of their shortcomings will be improved. The specific improvement is affected by the mixing ratio and other additives. Vinyl elastomer is made of copolymer of ethylene and propylene, the main components are ethylene-propylene binary copolymer and a small amount of diene styrene. This material has elasticity and softness similar to natural rubber; propylene-based elastomer is a new type of propylene / α-olefin copolymer series product with propylene as the main component and ethylene as the auxiliary component. It is produced by combining metallocene catalysis technology and solution polymerization process. It is a unique propylene-ethylene semi-crystalline copolymer; polyolefin elastomer is a random copolymer elastomer of ethylene and high-carbon α-olefin (such as 1-butene, 1-hexene, 1-octene, etc.). This structure makes POE have a two-phase structure, namely the amorphous region (rubber phase) formed by the soft chain curling structure generated by the α-olefin branch chain and the crystalline region (plastic phase) of the polyethylene chain segment. This structural feature gives POE high elasticity and thermoplasticity, making it have both the elasticity of rubber and the processability of plastic. It has good compatibility with polyolefins (such as PP, PE, etc.) and can be blended with them to improve the comprehensive performance of the material.

[0007] Hydrogenated Styrene-Butadiene Block Copolymer (Styrene Ethylene Butylene Styrene, SEBS) is a linear triblock copolymer with polystyrene as the terminal segment and ethylene-butene copolymer obtained by hydrogenating polybutadiene as the middle elastic block. This structure makes SEBS have both the hardness of polystyrene and the elasticity of polybutadiene, and can be used to toughen some plastics to improve their toughness and impact strength.

[0008] Based on the characteristics of vinyl elastomers, propylene elastomers, polyolefin elastomers and hydrogenated styrene-butadiene block copolymers, they can be used as additives to improve the upper and lower temperature tolerance and toughness of polyethylene and polypropylene mixed materials, making them more suitable for the preservation of foods such as corn. Summary of the invention

[0009] The present invention is made in view of the above problems, and its purpose is to provide a method for preparing a vacuum bag for corn packaging and a manufacturing process. In the corn vacuum bag packaging film, polypropylene is used as the main raw material, and hydrogenated styrene-butadiene block copolymer (SEBS), vinyl elastomer, propylene-based elastomer, and polyolefin elastomer are introduced to improve the ability of the packaging film to resist ultraviolet rays, oxygen and heat, and increase the stability and aging resistance of the packaging film.

[0010] The technical solution adopted by the present invention is as follows: In a first aspect, the present invention provides a method for preparing a vacuum bag for corn packaging. The raw materials include the following components in parts by weight: 30-70 parts of polypropylene (PP), 30-70 parts of polyethylene (PE), 5-20 parts of vinyl elastomer, 5-10 parts of propylene-based elastomer, 5-20 parts of polyolefin elastomer, 10-20 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 1-10 parts of stabilizer, 1-8 parts of adsorbent, 2-10 parts of antibacterial agent, 1-5 parts of antioxidant, and 10-25 parts of compatibilizer.

[0011] Furthermore, the stabilizer is D-sorbitol.

[0012] Furthermore, the antibacterial agent is chitosan.

[0013] Furthermore, the adsorbent is BYK-P4200.

[0014] Furthermore, the antioxidant is a hindered phenol antioxidant.

[0015] Furthermore, the compatibilizer includes maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted SEBS, and ethylene-vinyl acetate copolymer grafted maleic anhydride (EVA-g-MAH).

[0016] Furthermore, the maleic anhydride grafted SEBS is prepared by melt-induced solid-phase grafting of maleic anhydride to SEBS, and the maleic anhydride grafted SEBS is synthesized according to the following steps: (1) Place maleic anhydride in a vacuum drying oven and dry at 115-130 degrees Celsius for 10-12 hours; (2) Maleic anhydride, SEBS and initiator diisopropylbenzene peroxide (DCP) are added into a high-speed mixer according to the ratio and the three are fully mixed; (3) After mixing, the mixture is put into a twin-screw extruder for melt blending. After the extrusion material is uniformly extruded at a stable rate, the extrusion material is pulled through supercooled water to a pelletizer for pelletization to obtain unpurified maleic anhydride grafted SEBS particles; (4) Weigh the sample and place it in a three-necked flask. Slowly pour xylene into the flask to completely immerse the sample. Place the flask in an oil bath and continue heating for 18-25 minutes after reflux occurs. Then stop heating. At this time, the grafted material is completely dissolved. The solution is clear and transparent, and there is no wall adhesion.

[0017] (5) Pour the solution in the three-necked flask into 300-330 ml of acetone solution while it is still hot. The dissolved maleic anhydride grafted SEBS will quickly produce a white flocculent precipitate after the acetone solution is added. Let it stand and filter it. The obtained product is placed in a vacuum drying oven and dried at 75-95 °C for 8-12 h to constant weight to obtain purified maleic anhydride grafted SEBS.

[0018] (6) The grafting rate of purified maleic anhydride grafted SEBS was determined by acid-base titration.

[0019] Furthermore, in the synthesis preparation of the maleic anhydride grafted SEBS, in step (2), the components of maleic anhydride, SEBS and initiator dicumyl peroxide (DCP) are as follows, in terms of weight fractions: 100 parts of SEBS, 0.5-2 parts of maleic anhydride, and 0.2-0.4 parts of DCP.

[0020] Further, in the synthesis preparation of maleic anhydride grafted SEBS, in step (3), the parameters of the twin-screw extruder are set to a temperature of 170-200 degrees Celsius in zone 1, a temperature of 170-200 degrees Celsius in zone 2, a temperature of 180-200 degrees Celsius in zone 3, a temperature of 180-200 degrees Celsius in zone 4, a temperature of 180-200 degrees Celsius in zone 5, a temperature of 180-210 degrees Celsius in zone 6, a temperature of 170-200 degrees Celsius in zone 7, and a head temperature of 180-210 degrees Celsius; In a second aspect, the present invention further provides a process for manufacturing a vacuum bag for packaging corn.

[0021] The steps include: S1. Raw material preparation and pretreatment: placing the raw materials polyethylene, polypropylene, vinyl elastomer, propylene-based elastomer, polyolefin elastomer and hydrogenated styrene-butadiene block copolymer in a constant temperature drying oven for 4-5 hours, and the temperature of the constant temperature drying oven is set at 75-85 degrees Celsius; S2, feeding and conveying, adding raw materials and adsorbents, compatibilizers, stabilizers, antibacterial agents and antioxidants into the twin-screw extruder in batches; S3, heating and melting, the heating and melting temperature is 240-290 degrees Celsius; S4, plasticizing and mixing, the threads on the screw shear, extrude, and convey the materials to fully mix them; S5. Filter impurities. During the melting process, the impurities in the composite material are removed through the filter to ensure the purity of the film; S6, film extrusion, the molten composite material is uniformly extruded through the die head to form a continuous film strip; S7, pre-cooling, preliminary cooling of the just-extruded film, through air cooling or water cooling device to reduce the temperature of the film and preliminarily shape it.

[0022] S8, cold roller contact: guide the pre-cooled film onto the cold roller. The surface of the cold roller has been specially treated to have good cooling effect and smoothness, and the temperature of the cold roller is 20-25 degrees Celsius.

[0023] S9, cooling and shaping to obtain a finished film, and cutting it according to size, using a heat sealer to seal the cut film to form a closed space to make a vacuum bag.

[0024] Furthermore, the process parameters of the twin-screw extruder are: The temperature in zone 1 is 240-260 degrees Celsius, the temperature in zone 2 is 260-280 degrees Celsius, the temperature in zone 3 is 270-290 degrees Celsius; the temperature in zone 4 is 270-290 degrees Celsius; the temperature in zone 5 is 265-285 degrees Celsius; the temperature in zone 6 is 245-270 degrees Celsius; the temperature in zone 7 is 240-260 degrees Celsius; The head temperature is 200-230 degrees Celsius; the vacuum degree is 0.04-0.06 MPa; the main engine speed is 700-750 r / min; the feeding speed is 420-450 r / min; and the pelletizing speed is 400-650 r / min.

[0025] Furthermore, the final product is tested for relevant indicators.

[0026] The beneficial effects of the present invention are: (1) The present invention prepares a vacuum bag for packaging corn, which utilizes the characteristics of thermoplastic elastomer to improve the shortcomings of the polyethylene and polypropylene mixed material, so that the final composite material has a wider range of upper and lower limits of temperature tolerance, increases its toughness, and significantly reduces the bag breakage rate.

[0027] (2) The present invention prepares a corn packaging vacuum bag, prepares modified maleic anhydride grafted SEBS, explores and uses maleic anhydride grafted SEBS with the highest grafting rate as one of the raw materials for making vacuum bags, solves the problem of poor compatibility between SEBS and other raw materials, allows SEBS and other raw materials to be fully mixed, and fully integrates the characteristics of SEBS material.

[0028] (3) The present invention prepares a corn packaging vacuum bag, in which an adsorbent is added during the manufacturing process, which significantly reduces the content of volatile organic compounds in the composite material and reduces the potential threat to health.

[0029] (4) The corn packaging vacuum bag prepared by the present invention uses D-sorbitol as a stabilizer, which generates hydrogen bonds with carbonyl groups, oxide groups and other groups in plastic molecules, weakens the interaction between plastic molecular chains, and enhances the mobility of molecular chains, thereby improving the flexibility, ductility and other properties of plastic products, and is safe for human body and environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a practical application diagram of a corn packaging vacuum bag of the present invention; Figure 2 It is a relationship diagram between the VOC content of a vacuum bag for corn packaging and the content of adsorbent added to the raw materials of the present invention; Figure 3 It is a relationship diagram between the tensile strength of a corn packaging vacuum bag of the present invention and the content of adsorbent added to the raw material; DETAILED DESCRIPTION The following is a detailed description of embodiments of the present invention, but the present invention can be implemented in many different ways as defined and covered by the claims.

[0031] Example 1 A method for preparing a vacuum bag for corn packaging, wherein maleic anhydride grafted SEBS is synthesized and prepared, and the grafting rate is determined by acid-base titration. The grafting rates of different raw material ratios are shown in Table 1: When the amount of SEBS and DCP added remains unchanged, the data of groups 1-4 reveal that the grafting rate of maleic anhydride grafted SEBS shows an upward trend with the increase of maleic anhydride dosage. This is because, when the number of free radicals generated in the entire reaction system is fixed, the increase in maleic anhydride content increases the probability of collision with free radicals, so that more maleic anhydride can be grafted onto the molecular chain of SEBS, which is manifested as an increase in the grafting rate of the sample. On the other hand, it can be seen from the data of groups 3 and groups 5-8 that when the amount of SEBS and maleic anhydride added is fixed, when the amount of DCP added increases from 0.20 to 0.35, the grafting rate of maleic anhydride grafted SEBS also increases. This is because the increase in the amount of DCP leads to an increase in the number of free radicals in the system, which makes it easier for maleic anhydride to collide with free radicals, and the grafting rate therefore shows a clear upward trend. However, when the DCP content in the system further increases from 0.35 to 0.40, the grafting rate of maleic anhydride grafted SEBS decreases. This is because as the DCP content increases, the number of SEBS molecular chain free radicals also increases accordingly, resulting in an increased probability of SEBS free radicals colliding with each other. In this case, the homopolymerization of the monomers and the grafting reaction form a competitive relationship, which not only reduces the grafting rate, but also generates a large amount of monomer homopolymers, which has an adverse effect on the grafting reaction.

[0032] The acid-base titration method is as follows: first, accurately weigh 2.0 g of the purified grafted material and put it into a distillation flask, then pour 110 ml of xylene into each distillation flask, and add zeolite to prevent violent boiling. Then start heating to gradually dissolve the grafted material. After about 20 minutes, the reflux phenomenon is observed. Continue heating for about 20 minutes and then stop heating. Wait for the solution to cool naturally to a room temperature of 70°C. At this time, the grafted material sample has been completely dissolved in xylene, but there is a small amount of residue on the wall of the bottle. At the same time, prepare 0.1 mol / L potassium hydroxide-ethanol standard solution and 0.1 mol / L hydrogen chloride-isopropanol standard solution for standby use. Next, add 15 ml of potassium hydroxide-ethanol standard solution to the cooled solution, reheat to reflux, stop heating after 10 minutes, and then add 4-5 drops of phenolphthalein reagent to the solution, and the solution will turn dark red at this time. While the solution is still warm, use 0.1 mol / L hydrogen chloride-isopropanol standard solution to back-titrate the excess potassium hydroxide-ethanol until the solution becomes clear and the color no longer changes within half a minute, that is, the reaction endpoint is reached. Stop the titration at this time and record the actual usage of the two standard solutions. Finally, according to the following calculation formula, use these data to calculate the grafting rate of maleic anhydride grafted SEBS, and average the three sets of experimental data to obtain the average value, which is the grafting rate of the sample.

[0033] Where: Grafting rate of maleic anhydride grafted SEBS, % V KOH —Consumption volume of potassium hydroxide-ethanol standard solution, L C KOH —Concentration of potassium hydroxide-ethanol standard solution, mol / L V HCl —Consumption volume of hydrogen chloride-isopropanol standard solution, L C HCl —Concentration of hydrogen chloride-isopropanol standard solution, mol / L M MAH —Relative molecular weight of maleic anhydride (MAH) (M=98.06 g / mol) m—mass of maleic anhydride grafted SEBS after purification, g; Furthermore, the synthesis preparation steps of the maleic anhydride grafted SEBS are: (1) Place maleic anhydride in a vacuum drying oven and dry at 120 degrees Celsius for 12 hours; (2) Maleic anhydride, SEBS and initiator dicumyl peroxide (DCP) are added into a high-speed mixer according to the proportions and the three are fully mixed. The components of maleic anhydride, SEBS and initiator dicumyl peroxide (DCP) are as follows, in terms of weight fractions: 100 parts of SEBS, 0.5-2 parts of maleic anhydride, and 0.2-0.4 parts of DCP; (3) After mixing, the mixture is put into a twin-screw extruder for melt blending. After the extrusion material is uniformly extruded at a stable rate, the extrusion material is pulled through supercooled water to a pelletizer for pelletization to obtain unpurified maleic anhydride grafted SEBS particles; (4) Weigh the sample and place it in a 250 ml three-necked flask. Measure 100 ml of xylene and slowly pour it into the three-necked flask to completely immerse the sample. Place the three-necked flask in an oil bath and continue heating for 22 minutes after reflux occurs. Then stop heating. At this time, the grafted material is completely dissolved. The solution is clear and transparent, and there is no wall adhesion.

[0034] (5) Pour the solution in the three-necked flask into 300 ml of acetone solution while it is still hot. The dissolved maleic anhydride grafted SEBS will quickly produce white flocculent precipitation after adding the acetone solution. Let it stand and filter it. The obtained product is placed in a vacuum drying oven and dried at 90°C for 12 hours to constant weight to obtain purified maleic anhydride grafted SEBS. Furthermore, in the synthesis preparation of the maleic anhydride grafted SEBS, in step (3), the parameters of the twin-screw extruder are set as follows: zone 1 temperature 180 degrees Celsius, zone 2 temperature 185 degrees Celsius, zone 3 temperature 190 degrees Celsius, zone 4 temperature 190 degrees Celsius, zone 5 temperature 190 degrees Celsius, zone 6 temperature 185 degrees Celsius, zone 7 temperature 180 degrees Celsius, and die head temperature 200 degrees Celsius.

[0035] Example 2 According to the grafting rates of different groups of maleic anhydride grafted SEBS in Example 1, the maleic anhydride grafted SEBS (Group 4) with the best grafting rate is selected as part of the compatibilizer in the raw material, a method for preparing a vacuum bag for corn packaging, calculated by weight: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0036] Furthermore, the stabilizer is D-sorbitol, which changes the structure and properties of plastic molecules by interacting with plastic molecules. Specifically, hydrogen bonds occur between the hydroxyl groups in the sorbitol molecules and the carbonyl groups, oxide groups and other groups in the plastic molecules, thereby weakening the interaction between the plastic molecular chains, enhancing the mobility of the plastic molecular chains, and improving the flexibility, ductility and other properties of the plastic products. In addition, D-sorbitol can also play the role of an antioxidant and ultraviolet absorber in the plastic, preventing the plastic products from discoloring and aging in the sun, thereby extending the service life of the plastic products.

[0037] Furthermore, the antibacterial agent is chitosan, which is a natural high molecular polymer with broad-spectrum antibacterial properties. It can inhibit the growth and reproduction of bacteria by interacting with bacterial cell membranes and destroying their structures. Adding chitosan to plastics can give plastic products antibacterial properties, enabling them to effectively inhibit the growth of various bacteria such as Escherichia coli and Staphylococcus aureus, effectively extend the service life of plastic products, and reduce health risks caused by bacterial growth. It can improve the toughness, impact resistance and heat resistance of plastics, making plastic products more durable and practical. In addition, chitosan can also increase the surface gloss of plastics, making them more beautiful.

[0038] Furthermore, the adsorbent is BYK-P4200, which can significantly reduce the content of volatile organic compounds. This is of great significance for improving the environmental performance of plastic products and reducing pollution to the environment. By adding BYK-P4200, the VOC released during the production and use of plastic products can be effectively reduced, thereby meeting more stringent environmental regulations.

[0039] Further, the antioxidant is a hindered phenol antioxidant, specifically antioxidant 1010. In a molten state, due to the presence of high temperature and oxygen, plastics are prone to oxidation reactions and produce free radicals. These free radicals can trigger chain reactions and accelerate the aging and degradation of plastics. One of the main functions of hindered phenol antioxidants is to capture these free radicals and convert them into stable molecules, thereby blocking the chain reaction and reducing the oxidation rate. This mechanism effectively delays the aging process of plastics and improves the service life and stability of the product.

[0040] Furthermore, the compatibilizer includes 4 parts of maleic anhydride grafted PP, 4 parts of maleic anhydride grafted PE, 10 parts of maleic anhydride grafted SEBS, and 2 parts of ethylene-vinyl acetate copolymer grafted maleic anhydride (EVA-g-MAH).

[0041] Furthermore, the raw materials of the maleic anhydride grafted SEBS used in this embodiment are as follows: maleic anhydride, SEBS and initiator dicumyl peroxide (DCP), in parts by weight, SEBS 100 parts, maleic anhydride 2 parts, DCP 0.3 parts.

[0042] Furthermore, a corn packaging vacuum bag preparation process comprises the following specific steps: S1. Raw material preparation and pretreatment: the raw materials polyethylene, polypropylene, vinyl elastomer, propylene-based elastomer, polyolefin elastomer, and SEBS are placed in a constant temperature drying oven at 80 degrees Celsius and dried for 5 hours; S2, feeding and conveying, taking out the raw materials from the constant temperature drying oven, weighing the corresponding mass parts, and feeding them into the twin-screw extruder according to the proportion, and adding stabilizer, adsorbent, antibacterial agent, antioxidant and compatibilizer at the same time, and the feeding speed is 430r / min; S3, heating and melting, the raw material particles are heated and melted in the twin-screw extruder to form a uniform plastic melt. In this process, the main engine speed is 750 r / min and the heating and melting temperature is 270 degrees Celsius; S4, plasticizing and mixing, the threads on the screw shear, extrude, and convey the materials. Under the combined effects of heating and shearing force, the materials gradually melt and plasticize, and are fully mixed; S5. Filter impurities: During the melting process, impurities in the resin are removed through the filter to ensure the purity of the film.

[0043] S6. Film extrusion: The molten mixed raw materials are evenly extruded from the die to form a continuous film strip.

[0044] S7, pre-cooling: Preliminary cooling of the newly extruded film, through a water cooling device to reduce the temperature of the film and preliminarily shape it.

[0045] S8, cold roller contact: guide the pre-cooled film onto the cold roller. The surface of the cold roller has been specially treated to have good cooling effect and smoothness. The temperature of the cold roller is 20 degrees Celsius.

[0046] S9, Cooling and shaping: The film fits tightly on the cold roller, and is further shaped and solidified through the rolling and cooling effect of the cold roller, ensuring the dimensional stability and surface gloss of the film to obtain the final product.

[0047] Furthermore, in the process for preparing a corn packaging vacuum bag, in step S2, the process parameters of the twin-screw extruder are: The temperature of zone 1 is 250 degrees Celsius, the temperature of zone 2 is 270 degrees Celsius, the temperature of zone 3 is 280 degrees Celsius; the temperature of zone 4 is 280 degrees Celsius; the temperature of zone 5 is 280 degrees Celsius; the temperature of zone 6 is 265 degrees Celsius; the temperature of zone 7 is 255 degrees Celsius; The head temperature is 225 degrees Celsius; the vacuum degree is 0.05 MPa; the main engine speed is 750 r / min; the feeding speed is 430 r / min; and the pelletizing speed is 550 r / min.

[0048] Furthermore, the final product is tested for relevant indicators, including but not limited to: VOC analysis, tensile strength, water vapor permeability, and elongation at break. The testing is based on GB / T 27740-2011 "Cast Polypropylene (CPP) Film"; GB 4806.7-2023 "National Food Safety Standard Food Contact Plastic Materials and Products".

[0049] Furthermore, the VOC analysis and determination method are as follows: using a gas chromatograph, 20 mL of 10% acetone solution is configured to fill two-thirds of the headspace bottle, and 0.3 g of the particle material to be tested is weighed and placed in the headspace bottle. When the temperature rises to the set temperature, the air and hydrogen are turned on and the partial pressure is adjusted to 0.4 MPa, and then ignited by the FID device, and the spectrum is drawn by the program control of the headspace sampler, and finally the total peak area is obtained.

[0050] Example 3 Compared with Example 2, the only difference in Example 3 is that the formula of the corn packaging vacuum bag is different: 50 parts of polypropylene, 50 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0051] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0052] Example 4 Compared with Example 2, the only difference in Example 4 is that the formula of the corn packaging vacuum bag is different: 30 parts of polypropylene, 70 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0053] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0054] Example 5 Compared with Example 2, the only difference in Example 5 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 10 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0055] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0056] Example 6 Compared with Example 2, the only difference in Example 6 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 20 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0057] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0058] Example 7 Compared with Example 2, the only difference in Example 7 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 10 parts of compatibilizer.

[0059] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0060] Example 8 Compared with Example 2, the only difference in Example 8 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer, 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 25 parts of compatibilizer.

[0061] The compatibilizer includes 5 parts of maleic anhydride grafted PP, 5 parts of maleic anhydride grafted PE, 12 parts of maleic anhydride grafted SEBS, and 3 parts of ethylene-vinyl acetate copolymer grafted maleic anhydride (EVA-g-MAH).

[0062] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0063] Comparative Example 1 Compared with Example 2, the only difference in Comparative Example 1 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer (D-sorbitol), 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 5 parts of compatibilizer.

[0064] The compatibilizer includes 1 part of maleic anhydride grafted PP, 1 part of maleic anhydride grafted PE, 2 parts of maleic anhydride grafted SEBS, and 1 part of ethylene-vinyl acetate copolymer grafted maleic anhydride (EVA-g-MAH).

[0065] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0066] Comparative Example 2 Compared with Example 2, the only difference in Comparative Example 2 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 5 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer (D-sorbitol), 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0067] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0068] Comparative Example 3 Compared with Example 2, the only difference in Comparative Example 3 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 0 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer (D-sorbitol), 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0069] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0070] Comparative Example 4 Compared with Example 2, the only difference in Comparative Example 4 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer (D-sorbitol), 5 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 0 parts of compatibilizer.

[0071] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0072] Comparative Example 5 Compared with Example 2, the only difference in Comparative Example 5 is that the formula of the corn packaging vacuum bag is different: 60 parts of polypropylene, 40 parts of polyethylene, 10 parts of vinyl elastomer, 5 parts of propylene elastomer, 8 parts of polyolefin elastomer, 15 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 6 parts of stabilizer (D-sorbitol), 0 parts of adsorbent, 8 parts of antibacterial agent, 4 parts of antioxidant, and 20 parts of compatibilizer.

[0073] The preparation process and other relevant parameters of this embodiment are consistent with those of embodiment 2.

[0074] Table 2 Mechanical properties of vacuum bags and water vapor transmission test data Combined with the data of Example 2-Example 4, it is shown that within a certain range, as the ratio of polypropylene to polyethylene increases, the mechanical properties of the produced vacuum bag show a trend of first increasing and then decreasing. When the proportions of other raw materials remain unchanged, 60 parts of polypropylene and 40 parts of polyethylene, the mechanical properties of the produced vacuum bag are the best; combined with the data of Example 2, Example 5, Example 6, Comparative Example 2 and Comparative Example 3, it is shown that when the proportions of other raw materials remain unchanged, 10-20 parts of hydrogenated styrene-butadiene block copolymer (SEBS) are used, the mechanical properties of the produced vacuum bag meet the standards. If SEBS is not included in the raw materials, the mechanical properties of the produced vacuum bag are as follows: The mechanical properties of the vacuum bag produced are relatively poor. After adding a small amount of SEBS, the mechanical properties of the vacuum bag produced are greatly enhanced, and with the increase of the amount of SEBS added, the mechanical properties of the vacuum bag show a phenomenon of first increasing and then weakening. The best effect is achieved when the amount of SEBS added is 15 parts. Combining the data of Example 2, Example 7, Example 8, Comparative Example 1 and Comparative Example 4, it is shown that when the parts of other raw materials remain unchanged and the compatibilizer is 10-25 parts, the mechanical properties of the vacuum bag produced meet the standards. If the raw material does not contain the compatibilizer, the mechanical properties of the vacuum bag produced are relatively poor. After adding a small amount of compatibilizer, the mechanical properties of the vacuum bag produced are slightly enhanced, and with the increase of the compatibilizer, the mechanical properties of the vacuum bag produced are slightly enhanced. With the increase of the amount of compatibilizer added, the mechanical properties of the vacuum bag showed a phenomenon of first increasing and then weakening. The best effect was achieved when the amount of compatibilizer added was 20 parts. Without the addition of compatibilizer, the compatibility between the raw materials was poor, and the water vapor permeability of the vacuum bag produced did not meet the standard. Based on the above data, although SEBS has a better enhancing effect on the mechanical properties of the vacuum bag than the compatibilizer, when SEBS or the compatibilizer exists alone, the enhancing effect on the mechanical properties of the vacuum bag is limited. When the compatibilizer and SEBS exist together, the two have a synergistic effect and significantly improve the mechanical properties of the vacuum bag. This is because the SEBS molecular chain does not contain polar or reactive groups, which limits its interaction with polar polymers. The compatibility of SEBS is enhanced after the main component of the compatibilizer, maleic anhydride grafted SEBS, is blended with SEBS, which enhances the compatibility of SEBS with other raw materials, significantly improves the mechanical properties and processing properties of the vacuum bag, and reduces the breakage rate of the vacuum bag in practical applications. The other components of the compatibilizer, maleic anhydride grafted PP, maleic anhydride grafted PE, and ethylene-vinyl acetate copolymer grafted maleic anhydride, enhance the compatibility of PP, PE, and propylene-based elastomers. The final vacuum bag has the characteristics of PE and good low-temperature resistance, which is conducive to the low-temperature preservation of the vacuum bag and its internal products, and the characteristics of PP and good high-temperature performance. The vacuum bag can be directly heated.

[0075] according to Figure 1Combining the data of Example 2 with that of Comparative Example 5, the addition of adsorbent in the raw material can effectively reduce the VOC content in the vacuum bag. When the adsorbent addition amount reaches 5 parts, the VOC content in the vacuum bag drops to a lower level. Thereafter, continuing to increase the amount of adsorbent has almost no effect on the VOC content. Considering factors such as cost, it is believed that the reduction in the VOC content of the composite material is optimal when the adsorbent addition amount reaches 5 parts.

[0076] according to Figure 2 The number of adsorbents will affect the tensile strength of the vacuum bag. When the adsorbent addition amount is 0-5 parts, the tensile strength of the vacuum bag increases with the increase of the adsorbent addition amount. When the adsorbent addition amount is 5-7 parts, the tensile strength of the vacuum bag has no obvious change. Continue to add adsorbent. When the adsorbent reaches 8 parts, the tensile strength of the vacuum bag can still increase slightly.

[0077] Example 2 is the best group of the present invention. After commissioned inspection, the report number is 1624030024001, and the test results are: after inspection, the samples of the present invention meet the requirements of GB / T 27740-2011 "Cast Polypropylene (CPP) Film" standard.

Claims

1. A method for preparing a corn packaging vacuum bag, characterized in that: The formula is calculated by weight, and its raw materials include the following components: 30-70 parts of polypropylene (PP), 30-70 parts of polyethylene (PE), 5-20 parts of vinyl elastomer, 5-10 parts of propylene elastomer, 5-20 parts of polyolefin elastomer, 10-20 parts of hydrogenated styrene-butadiene block copolymer (SEBS), 1-10 parts of stabilizer, 1-8 parts of adsorbent, 2-10 parts of antibacterial agent, 1-5 parts of antioxidant, and 10-25 parts of compatibilizer.

2. The method for preparing a corn packaging vacuum bag according to claim 1, characterized in that: The compatibilizer includes maleic anhydride grafted PP, maleic anhydride grafted PE, maleic anhydride grafted SEBS, and ethylene-vinyl acetate copolymer grafted maleic anhydride (EVA-g-MAH).

3. The method for preparing a corn packaging vacuum bag according to claim 2, characterized in that: The maleic anhydride grafted SEBS is synthesized according to the following steps: a. Place maleic anhydride in a vacuum drying oven and dry at 115-130 degrees Celsius for 10-12 hours; b. Add maleic anhydride, SEBS and initiator dicumyl peroxide (DCP) into a high-speed mixer according to the proportions and mix the three thoroughly; c. After mixing, the mixture is put into a twin-screw extruder for melt blending. After the extrusion material is uniformly extruded and the rate is stabilized, the extrusion material is pulled through cold water to a pelletizer for granulation to obtain unpurified maleic anhydride grafted SEBS particles; d. Weigh the sample and place it in a three-necked flask. Slowly pour xylene into the three-necked flask to completely immerse the sample. Place the three-necked flask in an oil bath and continue heating for 18-25 minutes after reflux occurs. Then stop heating. At this time, the grafted material is completely dissolved. The solution is clear and transparent without wall adhesion. e. Pour the solution in the three-necked flask into 300-330 ml of acetone solution while it is hot. The dissolved maleic anhydride grafted SEBS will quickly produce white flocculent precipitation after adding the acetone solution; let it stand and filter it by suction. The obtained product is placed in a vacuum drying oven and dried at 75-95°C for 8-12h to constant weight to obtain purified maleic anhydride grafted SEBS; f. Determine the grafting rate of the purified maleic anhydride grafted SEBS.

4. The method for preparing a corn packaging vacuum bag according to claim 3, characterized in that: In the synthesis preparation of maleic anhydride grafted SEBS, in step b, the components of maleic anhydride, SEBS and initiator dicumyl peroxide (DCP) are as follows, by weight fraction: 100 parts of SEBS, 0.5-2 parts of maleic anhydride, and 0.2-0.4 parts of DCP.

5. The method for preparing a corn packaging vacuum bag according to claim 3, characterized in that: In the synthesis preparation of the maleic anhydride grafted SEBS, in step c, the parameters of the twin-screw extruder are set to a temperature of 170-200 degrees Celsius in zone 1, a temperature of 170-200 degrees Celsius in zone 2, a temperature of 180-200 degrees Celsius in zone 3, a temperature of 180-200 degrees Celsius in zone 4, a temperature of 180-200 degrees Celsius in zone 5, a temperature of 180-210 degrees Celsius in zone 6, a temperature of 170-200 degrees Celsius in zone 7, and a head temperature of 180-210 degrees Celsius.

6. A corn packaging vacuum bag manufacturing process, using the corn packaging vacuum bag manufacturing method according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Raw material preparation and pretreatment: placing the raw materials polyethylene, polypropylene, vinyl elastomer, propylene-based elastomer, polyolefin elastomer and hydrogenated styrene-butadiene block copolymer in a constant temperature drying oven for 4-5 hours, and the temperature of the constant temperature drying oven is set at 75-85 degrees Celsius; S2, feeding and conveying, adding raw materials and adsorbents, compatibilizers, stabilizers, antibacterial agents and antioxidants into the twin-screw extruder in batches; S3, heating and melting, the heating and melting temperature is 240-290 degrees Celsius; S4, plasticizing and mixing, the threads on the screw shear, extrude, and convey the materials to fully mix them; S5. Filter impurities. During the melting process, the impurities in the composite material are removed through the filter to ensure the purity of the film; S6, film extrusion, the molten composite material is uniformly extruded through the die head to form a continuous film strip; S7, pre-cooling, preliminary cooling of the just-extruded film, through air cooling or water cooling device to reduce the temperature of the film and preliminarily shape it; S8, cold roller contact, guide the pre-cooled film to the cold roller. The surface of the cold roller has been specially treated to have good cooling effect and smoothness. The temperature of the cold roller is 20-25 degrees Celsius. S9, cooling and shaping to obtain a finished film, and cutting it according to size, using a heat sealer to seal the cut film to form a closed space to make a vacuum bag; S10, testing the relevant indicators of the vacuum bag.

7. A corn packaging vacuum bag manufacturing process according to claim 6, characterized in that: In the method for preparing the corn packaging vacuum bag, in step S2, the process parameters of the twin-screw extruder are: The temperature in zone 1 is 240-260 degrees Celsius, the temperature in zone 2 is 260-280 degrees Celsius, the temperature in zone 3 is 270-290 degrees Celsius; the temperature in zone 4 is 270-290 degrees Celsius; the temperature in zone 5 is 265-285 degrees Celsius; the temperature in zone 6 is 245-270 degrees Celsius; the temperature in zone 7 is 240-260 degrees Celsius; The head temperature is 200-230 degrees Celsius; The vacuum degree is 0.04-0.06 MPa; the main engine speed is 700-750 r / min; the feeding speed is 420-450 r / min; the pelletizing speed is 400-650 r / min.

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