Polyester plastic (PET) bottle is one of the most important packaging containers. It is mainly used for pharmaceuticals, carbonated beverages, and can also be packaged in alcoholic beverages, tea beverages, juices, mineral water, edible oils, spices, cosmetics, pesticides, and Detergents and other liquid packaging. As a medicine packaging container, the PET bottle has various advantages. Firstly, the PET bottle is light in weight, easy to be molded, and the bottle body is firm. The strength and elasticity are significantly higher than those of other plastic materials, and can withstand considerable impact. Damaged, the most suitable for thin, light, high strength pharmaceutical bottles. After the advent of the early 1980s, the PET bottle source in China began to develop rapidly with an irresistible trend. Within a short period of 20 years, it has become the world's leading liquid and solid packaging form. In the field of pharmaceutical packaging applications, the PET bottle weighs about 1/10th of the glass bottle when the volume of the loaded drug is the same. The same outer diameter of the bottle, the PET bottle has 1.5 times the capacity of the glass bottle. Transparent or opaque brown bottles can be made from PET stock. Medicinal PET bottles have good gas barrier properties. Among commonly used plastics, PET bottles have the most excellent barrier to water vapor and oxygen and can fully meet the special storage requirements for pharmaceutical packaging. PET has excellent chemical resistance properties and can be used for packing all articles except strong alkalis and some organic solvents. The PET resin has a higher recycling rate than other plastics, and when burned as a waste, it has a combustion heat card. It is low in value and flammable and does not produce harmful gases. Food packaging made of PET meets food hygiene requirements because PET resin is not only a harmless resin, but also a pure resin without any additives. It passes quite strict food hygiene including the United States, Europe and Japan. The inspection of the law is considered as a qualified and safe packaging material for medicines and foods. Polyester resins are polymers that contain an ester group in the main chain of the polymer. Polyester applications generally refer to linear polyesters: polyethylene terephthalates. It is transparent, high tensile strength, good heat and low temperature resistance, non-toxic, light weight, good chemical stability, good barrier to oxygen and vapor, and good barrier to odor. These advantages make it a leader in plastics. At present, the world's production is growing at a double-digit rate. Pharmaceutical plastic bottles made of polyester as the main raw material are one of the most ideal varieties in terms of appearance, gloss, and physical and chemical properties.
Medicinal Polyester Bottle Main Processing Technology
1, the characteristics of medicinal polyester raw materials
The PET raw material used for bottle body blowing is saturated linear thermoplastic polyester. The main application performance index is: the intrinsic viscosity (IV) should be controlled at 70-85ml/g, so that the blow bottle has high mechanical strength and transparency. For inflated blow-molded bottle body (greater than 2 liters), the intrinsic viscosity of polyester raw material is 70-75ml/g. Injectable plastic injection small-volume bottles are preferred to use higher intrinsic viscosity index for production. Since the selection of raw materials is correct or not, it is related to the selection of molding process parameters in the production process and the quality of the bottles after molding. Therefore, in the production of pharmaceutical PET bottles, process data such as intrinsic viscosity, crystallization temperature, cooling rate, and orientation effect of the raw materials are particularly important because polyester is a crystallizable polymer with a very low crystallization rate. It is 6um/min(max). That is, by controlling the conditions of the crystallization temperature and the cooling rate, the polyester bottle can be made amorphous or crystalline, and the crystal type and quantity can be changed. The crystallinity required for polyesters is generally around 30%. At a temperature slightly higher than the glass transition temperature or slightly lower than the melting point, the crystallization rate of the polyester is small and the crystallization takes a long time. At a temperature of about 175° C., the crystallization time is much shorter. In short, the polyester is crystallized only by heating, and its crystallization process is slower, and it is possible to form larger spherulites with crystal grains, which refract light, make the product white, and have high brittleness. In addition, the crystallization rate of polyester decreases as its IV increases. The orientation allows the polyester molecules to be arranged in an orderly manner and promotes crystallization. The crystals formed are called strain-inducing crystals. The crystallites are small and do not refract light, so the oriented polyester article is transparent. If the partially oriented polyester sample is heat set and crystallized further, the sample is still transparent. Therefore, the crystallization and orientation are the key factors influencing the performance of the stretch blow molded polyester bottle in the molding process. If you want to make the bottle into a hot filling and can be used for the Pakistan-style disinfection treatment, you also need to heat-set the partially crystalline polyester to further crystallize to improve the heat resistance. Therefore, the technological characteristics of polyester raw materials, molecular crystallization and orientation are key factors in the quality characteristics of the process.
2. Dewetting and drying of polyester materials
Due to the processing of polyester, the moisture contained therein will rapidly deplete during the hydrolysis reaction with the polyester melt, ie moisture will show bubbles in the product. Hydrolysis will reduce the intrinsic viscosity of the polyester melt, but also affect the mechanical strength and performance of the product, while the polyester raw material is a hygroscopic polymer, so it should be strictly dried before processing to make its residual moisture content less than 0.005%. Polyester raw materials are dried using a desiccant drying system. As the dry hot air provided by the drying device enters the raw material from the bottom of the hopper, it absorbs the moisture contained in the raw material and returns to the drying device. In order to prolong the life of the dehumidifying bed in the desiccant device and maintain its efficiency, the humid air from the hopper is passed through a post-cooling device (which can be cooled with circulating water) so that the air temperature is lower than 65°C. Constant temperature control of the post-cooling unit is required to prevent the over-temperature air from entering the dehumidifying bed. The cooled air passes through the filter to remove airborne particles. The air is then dehumidified by the dehumidifying bed and finally returned to the drying hopper after being heated by the heater. Dryer drying conditions are generally selected raw materials: drying temperature 140 °C -180 °C, air dew point -40 °C, air volume 0.06 cubic meters / min (kg.h), drying time 4h. The mastery of these conditions should be noted; (1) When the air volume value is higher than 0.06 cubic meter/min (kg.h), the operation range can be widened, and the drying temperature can be lowered, and the energy consumption can be too high. (2) It is important to ensure that the dew point is as low as possible, but the dew point is as low as -10°C. However, it is also necessary to strictly monitor the dew point of the air. If it is found to be too high, it should be promptly reduced. (3) Drying temperature is a key parameter, and the optimum drying temperature can be determined by drying and measuring the intrinsic viscosity of the parison at various temperatures, typically from 150°C to 163°C. Drying temperature should be reduced to about 120°C when shutting down. (4) Longer drying time will reduce the intrinsic viscosity of polyester raw materials, and a reasonable understanding of the drying temperature becomes a key parameter. A small increase in temperature will result in a large decrease in the intrinsic viscosity of the polyester. Therefore, the drying time should be as short as possible in order to broaden the Operating range. In the drying process, due to the high drying temperature of the polyester, the hopper of the equipment should have good thermal insulation properties and be made of glass fiber as the heat insulation layer, the dry polyester material should be prevented from coming into contact with the outside air, because the polyester raw material will be fast Absorb moisture in the air. For example, when the completely dried polyester raw material is exposed to air with a relative humidity of 35% to 40% for 12 minutes, the moisture content reaches 0.005%.