Antibacterial absorbent base cooling containers

Abstract

Foam containers are used in packaging industries because they are lightweight, inexpensive, and durable. Due to the breakage and unsuitability of conventional absorbent containers for packaging in freezing tunnels, antibacterial absorbent base cold containers were designed and produced. Due to the different processing conditions and the structure of the polymers used, their processability is complex and difficult. In fact, in order to produce a product from incompatible polymers and create new properties, it is necessary to modify the composition and optimize the process conditions (including determining the appropriate process conditions including temperature, pressure, residence time, etc.). In order to prevent the growth of bacteria and premature spoilage of food, antibacterial compounds have been used in this invention. To produce antibacterial absorbent base cooling foam, first the polymer raw materials, absorbent materials, and antibacterial materials are combined together and through a special process of foam extrusion, antibacterial absorbent foam is produced. In the following production process, using a coating process, the polymeric materials and the manufactured flexible compound are combined and coated on the foam, and through the thermoforming process, antibacterial cold-absorbing containers are produced.

Description

Description of the invention Title of the invention Antibacterial absorbent base cooling containers Technical background of the relevant invention Polymer Engineering, Polymer Chemistry Technical problem and stating the objectives of the invention Human society is changing, evolving, rebuilding and renovating at an unexpected speed, and accepting these developments is the main condition for being in the current world. Therefore, the side effects of rapid developments and changes must also be accepted. Foam containers are used in the packaging industry because they are light, cheap and durable. For products such as fruits, vegetables, meat and fish, ordinary foam containers cannot be used due to the accumulation of water at the bottom of the container and early spoilage. In this research, by producing water-absorbent open-cell foam with antibacterial properties, food can be kept fresh for a long time by absorbing water from these products and the container being antibacterial. The antibacterial substances in the foam container prevent the growth of bacteria and prevent their transmission. Ordinary absorbent containers for packaging protein products must pass through a freezing tunnel at a temperature of minus 20 to minus 30 degrees Celsius.Due to the special and dry nature of this type of container, absorbent foam containers break during the packaging process at negative temperatures. In this project, by changing the process conditions and raw materials in foam extrusion and coating, low-temperature flexibility properties were added to this type of container. In the production of this type of container, these unique properties can be achieved by making a homogeneous alloy with a low glass transition temperature, which is a very complex task in the coating and foam extrusion process. (Table 1). Types of polystyrene foam Polystyrene foams are divided into two categories: open cell and closed cell, based on their cell structure: 1- Closed-cell polystyrene foam Regular closed-cell polystyrene foam is resistant to water penetration due to the closed cell membrane. These types of foams are soft and flexible and are used in the production of lidded containers. 2- Open cell polystyrene foam Open-cell polystyrene foam allows air to pass through the cells due to the pores in the foam structure. This type of foam is used in the production of dishware. Properties of polystyrene foam Most polystyrene foams have a closed-cell structure, which makes them suitable for use in disposable containers. The properties of polystyrene foams are influenced by their porous structure and the mechanical properties of the base polymer. Important and interesting properties of polystyrene foams include energy absorption, lightness, antibacterial, low thermal conductivity, thermoformability, ease of manufacture, etc. (Figure 1). Therefore, the objectives pursued in this invention are: 1- Following the sustainable development trend 2- Increasing foam quality and water absorption 3- Creating added value in the goods produced by industrial units and exporting them 4- Preventing the growth of bacteria and spoilage of food 5- Durable and flexible in the freezing tunnel 6- Economic efficiency and creating competition in the production of packaging containers A description of the state of the prior art and the history of developments related to the claimed invention. By reviewing the resources available on official patent websites such as the National Patent Office, USPTO, WIPO, EPO, etc., there is no similar subject to the claimed invention titled "Antibacterial absorbent base cooling containers". The reason for this is that this product has been produced for the first time in the country and its technology is in my possession as the CEO of Mazeron Foam Company. The lack of similar issues in international patent organizations is due to the lack of knowledge of the science of polymer compounds that can be used in the production of foam products with applicability in the construction industry. Providing a solution to an existing technical problem along with an accurate, sufficient, and integrated description of the invention The challenges of producing this product include: A- Optimization and selection of the amount of antibacterial compound and flexible compound to achieve foam with desired rheological and mechanical properties (end-use of the product). The first challenge in producing antibacterial absorbent base cold foam is its antibacterial level, which uses two different types of antibacterial materials and these compounds were tested at different doses to achieve the desired properties. In order to use flexible compound in foam coating, especially in polymer foam production, it is necessary to increase the properties of the melt, including elasticity and viscosity of the melt and its adhesion to the foam, and due to the use of two different types of polymers and single-phase alloying, it is a very complex task, which has been achieved by modifying the process and using physical and chemical compatibilizers to produce a single-phase alloy. The modifications applied in this part of the invention are very important for producing fine-cellular structural foam in order to create a process for absorbing and trapping liquids. Also, the use of nucleating agents (talc) is essential to create a fine-cellular structure.The fine-cell structure, compared to foams with a micro-cellular structure, results in liquids not returning to the upper surface or passing through the lower surface. In general, two types of antibacterial materials are used in this research: a compound (1 to 3 percent) for the antibacterial properties of the foam, and a flexible compound (30 to 40 percent) developed by the company's team was used to increase the flexibility of the container coating. Polymer foam is produced based on four steps including gas solubility in polymer, nucleation, growth and stabilization. In the first step, gas and polymer are combined and a two-phase mixture is formed, which with increasing temperature and time, gas particles dissolve inside the polymer chain and a supersaturated single-phase polymer / gas solution will be formed. In the second step, in order to form nuclei from gas bubbles, it is necessary to create a thermodynamic instability, which is achieved in two ways: increasing temperature or decreasing pressure, and in industries, the method of drastic pressure decrease is conventionally used. After the nucleation step, gas molecules penetrate into the formed nuclei and as a result, the cells enter the growth step. In the last step, the stability of the cells occurs through the cooling process, which results in no change in the cell structure after the aforementioned step. Extrusion foaming: In foaming extrusion, after gas mixing, nucleation and continuous cell growth are performed. Finally, cooling is performed when the foam is removed from the mold (the steps are described in the following order) (Figure 1). 1. Mixing: First, the materials are fed into the feeder according to the order in which they are added in the formulation and melted. After the materials are melted, gas is injected into the chamber and a two-component mixture of molten materials and gas (blowing agent) is formed. In this stage, several process factors, including screw speed, residence time, temperature and pressure of the desired area, are among the process factors that must be optimized so that a single-phase mixture of molten and gas is formed, in fact, the gas in the molten is completely dissolved. 2. Nucleation: After the mixing process, we enter the cell nucleation phase. In this stage, cell nuclei are formed by creating thermodynamic instability. For this stage, a severe pressure drop is applied to the system, due to which cell nuclei are formed and the gas particles around them cover it. 3. Cell growth: After the nuclei are formed and their energy levels are met, the cell growth stage takes place. In this stage, several process factors, including temperature, residence time, pressure, screw speed, and extruder screw type, are necessary to form a foam with a uniform structure and cells of similar sizes. 4. Stabilization: Stabilization of the foam's cellular structure is achieved in this stage by cooling it. Cooling speed, screw speed, temperature, and pressure are among the parameters that need to be optimized for this stage. In fact, accurate understanding of the foaming stages and the factors affecting them is the main condition for producing antibacterial absorbent cold polystyrene foam, which is designed depending on the production process, type of base polymer, foam application, and required properties. Several factors are effective in the production of polymer foam, including the following. 1. Material parameters: 1.1. Solutivity 1.2. Penetration 1.3. Surface tension 1.4. Viscosity 1.5.Elasticity 2. Process parameters 2.1. Pressure 2.2. Pressure drop rate 2.3. Temperature of different areas of the extruder 2.4.Die temperature 2.5. Screw speed 2.6. Residence time 2.7.Tension speed 2.8. Type and amount of blowing agent 3. Device parameters 3.1. Extruder type 3.2. Extruder length 3.3.Die type The various components of the foam extruder are as follows (Figure 1): 1-Material input area 2-Gas inlet area 3-First extruder (material melting area) 4- Cylinder and first screw 5-First extruder electric motor 6-Material transfer pipe from the first extruder to the second extruder 7- Cylinder and screw of the second extruder 8-Second extruder (cooling zone) 9-Die 10-Second extruder electric motor All of the above acknowledges the complexity of the foaming process and the high-tech nature of this technology, and hence optimizing the process for producing polystyrene foam for the production of antibacterial absorbent base cooling containers is considered the complexity of this invention. The ingredients used in the flexible compound are: 1-Polystyrene and high-density polyethylene based polymer (40-63 percent) 2- Physical stabilizer (15-30% by weight) 3-Chemical stabilizer (10-15) The ingredients used in the antibacterial compound are: 1-Base polymer (50-80 percent) 2-Compatibilizer (1-5% by weight) 3-Antibacterial substance (20-50% by weight) The ingredients used in absorbent foam are: 1-Polystyrene and polyethylene based polymer (90-95 percent) 2-Compatibilizer (1-3% by weight) 3-Agents to increase mechanical properties and nucleation (2-5% by weight) 4-Super absorbent compound (2-5% by weight) 5-Made antibacterial compound (1-3 percent) In the formulation, foaming conditions, including mixing zone temperature, die temperature, cooling section temperature, extruder pressure, and extruder screw speed, have been optimized, and the appropriate range for each is listed below in order to have absorbent polystyrene foam: - Foam production extruder parameters: -Melting and mixing zone temperature: 160-210°C -Die temperature: 120-130°C -Cooling section temperature: 70-100 degrees Celsius -Extruder pressure: 5-12 MPa -First extruder screw speed: 50-60 rpm -Second extruder screw speed: 15-20 rpm -Coating extruder parameters: -Screw diameter: 10-20 -Melting and mixing zone temperature: 190-250°C -Die temperature: 260-280°C B- Optimization of process conditions such as temperature of different areas of extruder, die temperature, cooling section temperature, stretching section temperature, extruder screw speed, stretching speed, die pressure and subsequent pressure drop should be done in accordance with the foam formulation and the device used. Unlike common polymers, starch is a polymer that is used in small amounts in the industry and hence its process settings are less known than common polymers. C- Another challenge of this invention is the foaming process and flexible coating and adjusting its process conditions to produce structural foam with a flexible and impact-resistant coating. Figure 2 shows a schematic of the thermoforming steps for producing antibacterial absorbent base cold containers, in which in part 1 the polymer sheet is heated by a heater, in part 2 the sheet is shaped by a mold and vacuum, and in part 3 the shaped container is cut and separated from the mold (Figure 2). The foaming process is a complex two-phase process that must first be converted from a two-phase state to a completely single-phase state and finally to a two-phase state in order to control the structural parameters and properties of the final product. Phase changes are performed by carefully adjusting the process conditions and optimizing the parameters. Extrusion foaming is one of the complex methods of producing polymer foams in which several factors are involved in optimizing the conditions. Figure 1 shows a number of material and process parameters affecting the foam production system.In addition to these parameters, machine parameters that are also important for foam production should be considered, including extruder zone temperature, die temperature, pressure control and pressure drop rate, screw speed, residence time, stretching speed, cooling speed, extruder type, and die type. Due to starch's sensitivity to heat and high melt flow index, process parameters such as barrel temperature, die temperature, shear stress, screw speed, and starch content are important for mixing with polystyrene and coating with a coating extruder. All of the above acknowledges the complexity of the foaming process and the high-tech nature of this technology. How to make the product: The production of this product includes two stages: compound production and structural foam production. 1. Production of flexible and antibacterial compound for foam containers In order to produce antibacterial absorbent structural foam, antibacterial compound was first produced and its rheological and mechanical properties were enhanced. A twin-screw extruder was used to produce this compound. In order to mix the compound completely, the temperature was 170-220°C and the screw speed was 15-20 rpm. To produce the compound, antibacterial materials (40-63%) and functionalizer (1-5%) were first dehumidified in an oven at 60-80°C. Then, they were combined with the base polymer and fed, and then mixed and melted. After the materials were removed from the die and cooled, the polymer strands were crushed using a granulator and ready for use for foaming. To produce the flexible compound, first 40-60% of polystyrene and high-density polyethylene base polymers, 15-30% physical compatibilizer, and 10-15% chemical compatibilizer are combined with the base polymer and fed into the feeding and melting zone. After the strands exit the die and cool, they are crushed using a granulator and ready for use for foaming and coating. 2. Production of antibacterial absorbent refrigeration polystyrene foam To produce structural polystyrene foam, it is necessary to use two series extruders (back to back), where the first extruder plays the role of melting and homogenizing the materials, and the second one plays the role of creating suitable conditions for cooling and cell stability (foaming). In this process, to produce foam, the first extruder is first fed. After melting and homogenization, the molten material is combined in the second extruder with butane gas as a blowing agent to form foam. In this invention, to produce an absorbent polystyrene micro-cell structural foam whose two outer faces have a closed cell structure and the formed middle layer has an open cell structure, the process conditions including the temperature of the first extruder, the foaming temperature (second extruder) and the pressure should be set in the temperature range of 170-220°C, 70-90°C and 90-135 bar, respectively. Figure 2 schematically shows the extruder used to produce this product. The foams produced in this invention have a cell size of 108-109cell / cm3 and a density of 0.3-0.5 g / cm3. The technical information of the invention is shown in Table 1. (Table 1) Explanation of shapes, maps and diagrams Table 1 - Polystyrene foam standards Figure 1 - Polystyrene foam production process Figure 2 - Schematic of thermoforming steps A clear and precise statement of the advantages of the claimed invention over prior inventions. According to the existing patents related to absorbent containers (Absorbent master batch chip composition for a polystyrene foam tray) with patent number WO2009151237A2 and (Production of absorbent polystyrene foam containers) with patent number 90394 (registered by me), these containers are not normally resistant to freezing tunnels and sub-zero temperatures and do not have antibacterial properties, and no invention has been registered in this field (antibacterial absorbent base cooling containers) so far. Therefore, the advantages of the invention in question are as follows: 1. More economical than conventional absorbent containers on sale 2. Durable packaging 3. Resistant to sub-zero temperatures and flexible 4. Impact resistant, flexible and high strength 5. Suitable dimensions and light weight 6. Absorbs 4-6 times more water and prevents spoilage of protein products 7. Has antibacterial properties, preserves and prolongs the shelf life of protein products. Description of at least one implementation method for implementing the invention This invention is used as a tray for packaging fresh meat products (such as chicken, meat and fish) for packaging in a freezing tunnel. Its function is that the moisture of the materials penetrates through the pores of the initial foam layer and is trapped in the middle structure, thus preventing the moisture from passing through; in addition, the fine cellular structure of the foam prevents liquids from returning to the upper surface or passing through the lower surface. Also, the creation of super-absorbent water properties in this foam has helped to absorb moisture faster. Due to the antibacterial compounds present in the foam, it prevents the growth of bacteria and the food remains healthy and fresh for a longer time. Due to the materials used in the foam and the coating of the containers and the manufacture of a special alloy in the production of these containers, it has caused that protein products have appropriate flexibility and do not break or deteriorate when packaged in the freezing tunnel. Explicit mention of the industrial application of the invention Although the invention in question is called an antibacterial absorbent base cooling container, the end consumer may be unfamiliar with this name, so the uses of this product are as follows: Food industries Packaging industries The industrial production line of this invention includes a twin-screw extruder for compound production, a single-screw extruder for foam production, a single-screw extruder for sheet production, and a vacuum thermoforming machine for forming trays. After compound production, its foam is produced by two single-screw extruders in series (back to back); melting and homogenization of compound granules in the first extruder under temperature conditions of 160-230 ° C and the foaming stage in the second extruder is carried out at a temperature of 70-90 ° C and butane gas injection. To produce foam, the pressure in the second extruder is suddenly reduced from 90-135 bar to atmospheric pressure. Simultaneously with foam production, a flexible sheet is produced on the opposite side using a single-screw extruder under temperature conditions of 190-250 ° C and with a screw speed of 10-20 rpm. Due to the rollers in this path, the sheet layer is placed under the foam layer and they stick together due to the heat on the rollers.The product produced at this stage is collected by a roll band and transferred to the vacuum thermoforming machine production line to produce the final product (water absorbent tray). In this machine, the roll is first unwound in the unwinder and guided into the machine by tension chains, which enter the heating zones at the entrance under a temperature of 200-180 degrees Celsius (the top and bottom of the roll are heated) (Thermo), then enter the molding zone (Figure 2), which is also accompanied by vacuum (Vacuum forming). After that, the desired container shape will be cut by cutting blades, and in the next step, the punch and the final product are produced.

Claims

Claim What is claimed: Claim 1) First, using polystyrene, polyethylene, antibacterial materials and absorbent compounds with specific process parameters, polystyrene foam was produced using an extruder. Then, using a coating extruder, antibacterial absorbent polystyrene foam was coated using impact-resistant polystyrene, heavy-duty polyethylene and some type of flexible and compatible material, and the antibacterial absorbent base was produced during the thermoforming process of cold containers. Claim 2) According to claim number 1, the complexities of this invention are optimization of the formulation, manufacturing of the flexible and antibacterial compound and its use in coating and extruder, which uses 8 types of formulations for coating and 3 types of formulations for extruder. In the formulation of the flexible compound, base polymer with different grades (70-85%), compatibilizer and flexible materials (15-30% by weight) are used. In the formulation of the antibacterial compound, base polymer (50-80%), compatibilizer (1-5% by weight) and antibacterial material (20-50% by weight) are used. In the final formulation for producing the absorbent base cooling foam, base polymer (90-95%), mechanical and nucleating agent (2-5% by weight), super absorbent compound (2-5% by weight) and antibacterial compound (1-3%) are used. Claim 3) The complexity of this invention is the optimization of extrusion foaming and coating process conditions, which in this invention, in order to create antibacterial properties in absorbent polystyrene foam and create flexibility of the final coated foam at sub-zero temperatures, in the formulation of foaming and coating conditions, including the temperature of the mixing zone (160-210 ° C), die temperature (130-120 ° C), cooling section temperature (100-70 ° C), extruder pressure (12-5 MPa) and first extruder screw speed (60-50 rpm), second extruder screw speed (15-20 rpm) and coating conditions including extruder screw speed (10-20 rpm), melting and mixing zone temperature (190-255 ° C) and die temperature (260-270 ° C) have been optimized. After the antibacterial absorbent base cooling foam is produced and removed from the die, it is coated with a flexible coating in the next step of the process, and in the next step, in the vacuum thermoforming process, which has 4 parts: heating, molding with vacuum, cutting with a blade, and punching. After passing through these steps, the antibacterial absorbent base cooling foam becomes the final container. Claim 4) Two continuous single-screw extruders are used to produce antibacterial absorbent polystyrene foam, the components of which consist of a cylinder, screw, polymer material and additive feeder, liquid butane gas injection feeder, pressure breaker plate, cold water circulation system, foam forming mold, heating elements, and motor.

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