In recent years, there has been a rapid development in the packaging of pharmaceutical plastic bottles in China. Pharmaceutical plastic bottle packaging has the advantages of light weight, no damage, and hygiene, and meets the special requirements of pharmaceutical packaging. At present, in terms of pharmaceutical tablets and capsule packaging, it has gradually achieved "plastic" and "glass". The application of high-quality medicinal plastic bottles is inseparable from reasonable bottle structure design, perfect production equipment and mature process methods. This article expounds the overall production process of medicinal plastic bottles from four aspects: the production characteristics of plastic bottles, the structure design, the molding method and the molding process characteristics.
1. Plastic bottle shape and shape features
At present, the shape of medical plastic bottles is round, square, oval and so on. The round bottle body has the largest amount of use. Its characteristic is that the wall thickness is relatively uniform, the ability to absorb impact energy is high, and the production cost is low, but the utilization rate of the effective area during storage or transportation is low. The effective area of ​​the square or rectangular bottle is high in the utilization rate and the stability is good, but the bulging phenomenon is more likely to occur. The specifications of plastic bottles are not yet clearly defined and are generally based on the needs of users and the nature of the drugs. In addition to the nominal capacity of the plastic bottle, there is also a full mouth capacity, which is larger than the nominal capacity. The specific requirements are determined by the diameter of the bottle mouth and the height of the bottle. Take small and medium-sized plastic bottles as an example, analyze the structural characteristics of plastic bottles, bottle necks, bottle shoulders, bottles and bottoms.
1.1 bottle structure features
For plastic bottles containing tablets and capsules, the design of the diameter of the bottle mouth is mainly designed to accommodate a single volume of the drug plus an appropriate space, which not only satisfies the need for mechanical charging, but also facilitates the convenience of the patient when taking the drug. The cross-sectional shape of the thread shape at the plastic neck portion is mostly semi-circular, seen from the outside as two fine threads. There are also trapezoidal threads, called single-head threads. The design of the bottle-neck and neck-thread form is mainly determined by the good compatibility with the bottle cap, because the moisture-blocking performance of the medicine package largely depends on the tightness after the application of the torsional force between the bottle mouth and the bottle cap. Here is the main part that reflects the excellent sealing performance of the bottle mouth. After the plastic bottle is filled with the drug, a capping machine with an adjustable torsional force should be used to screw the cap. The torque can be selected according to the relevant standards and the diameter of the cap. The matching of the size of the bottle and the lid is an important prerequisite for moisture resistance, and the tightness of the lid is the key to the advantages and disadvantages of the moisture barrier effect. In order to ensure the safety of drugs, we must first improve the sealing of the bottle mouth and increase the moisture-blocking effect. At present, plastic bottle mouths are all sealed with electromagnetic induction with aluminum foil gaskets, while bottle caps are mostly made with anti-theft caps. This kind of anti-theft cover can provide visible marks for the damage of the seal. Its structure is mainly a hole along the side skirt bottom around the bottle cap to form a break line. When the bottle cap is twisted, since the corrugated pawl is locked under the convex ring at the lower end of the bottle mouth, the anti-rotation cover can break along the disconnection line and the locking ring to discriminate whether the medicine has been opened after packaging. It is also very convenient to open and re-apply as a patient.
1.2 Bottleneck and bottle shoulder structure features
The shape of the medicinal plastic bottle adopts more circular bottles. The anatomy of the bottle body is longitudinally dissected. The bottleneck and the shoulder of the bottle are composed of two tangent arc radii, and the rotator is divided into two sections from the tangent point. The design needs to calculate the distance between the bottleneck and the centerline (radius), the radius of the shoulder, and the arc radius of the neck, and accordingly, the bottleneck and the total height of the bottle shoulder are obtained. The main factor affecting the strength of the bottle shoulder is the angle of inclination of the bottle shoulder. When the shoulder is too flat, the bottle body is prone to collapse. Therefore, when the bottle shoulder length is 10 mm, the shoulder inclination angle should exceed 15 degrees. The thickness should not be less than 1mm in order to ensure that the bottle does not suffer from shoulder breakage during handling and storage of the drug and its use.
1.3 Bottle structure features
The bottle body is a cylindrical, circular body. The requirement for the bottle body is uniform wall thickness. Excessive bottle wall thickness will increase the weight of the bottle body. The consumption of raw materials will increase. At the same time, the stress in the bottle body will increase and the shrinkage will increase. The bottle wall is too thin to be blow molded and has low strength. The general requirement is that the wall thickness of the other parts should be uniform except for the stiffeners and thread parts at the bottle mouth that are larger than the thickness of the bottle body. In order to improve the barrier properties and strength of plastic bottles, the thickness of the bottle body is generally 1.2 to 1.5 mm and tends to increase.
1.4 Bottle bottom structure features
At present, the design of the bottom of the medicinal plastic bottle adopts a convex bottom or a flat bottom, and most of the double-rounded structures are used. The convex bottom, which is the center of the bottom of the bottle, is raised into the bottle to form an arch, which can enhance the internal pressure resistance of the bottle body and ensure the stability of the bottle body. Blow molding also avoids plastic collapse and makes the bottom of the bottle uniform in thickness. The flat-bottomed double-rounded bottom structure is mostly suitable for large-volume bottles, and it can better withstand internal pressure.
2. The use of plastic bottles in pharmaceutical packaging
The technical personnel of a pharmaceutical plastic bottle manufacturing enterprise should first understand the chemical and physical properties of the medicines packaged in the produced vials, and then it should be clear whether the raw materials and auxiliary materials selected for the bottles have an effect on the packaged drugs. If a plastic bottle is used with improper dosage, the migration of trace components will change the medicinal effect of the drug and even endanger the life of the person taking the drug. Drugs are a special commodity. Manufacturers of pharmaceutical plastic bottles should strictly control the hygiene from every production link, and must comply with the relevant requirements of “GM P†and also have relevant laws and regulations.
3. Plastic bottle production equipment molding method
At present, China's production of plastic bottle equipment molding methods are mainly the following: 1 extrusion blow molding; 2 injection blow molding; 3 extrusion blow molding; 5 injection blow molding. There are differences in the performance structure of the products produced by these four molding methods. The use of injection-blow molding equipment for small pharmaceutical plastic bottles is generally welcomed by pharmaceutical manufacturers, because in the process of molding the bottle produced by injection blow molding, the injection nozzle of the equipment can be used to inject the injection molding of the bottle mouth. The accuracy of the bottle mouth, and then blown by the mechanical configuration of the mandrel to ensure the accuracy of the plastic bottle body dimensions, when the bottle filled with drugs, can effectively prevent the bottle of drug gas volatility and external gas into the bottle penetration. Since the injection blow molding machine needs a parison mold and a blow mold, the equipment cost is higher than the extrusion blow molding equipment.
4. Process Characteristics of Injection Blow Molded Plastic Bottles
4.1 Injection Blow Molding of Thermoplastic Polyester Bottles (PET)
The polyester used for blow-molding (PET) is a saturated linear thermoplastic polyester, and the intrinsic viscosity (IV) of blow-molded PET is 70 to 80 ml/g. It is used to blow small-volume plastic bottles. 1 barrel temperature parameters: the general temperature of the front barrel can take 265 °C -275 °C, the barrel temperature is 280 °C -290 °C, after the barrel temperature is 260 °C -255 °C. PET is a hygroscopic polymer, raw materials must be dehumidified and dried, drying temperature is generally 150 °C -163 °C, time is 5 hours, when the shutdown temperature should be reduced to about 120 °C, so that the water content of about 0.05%, Keep warm. The degree of particle drying in PET has a great influence on the molding performance. Dry PET should be prevented from coming into contact with the outside air because the dry PET raw material will quickly absorb the moisture in the air. 2 Note Blower parison temperature: In order to ensure the transparency of the parison, when the melt is filled into the parison mold, it should be cold and coarse 45°C, which is higher than the glass transition temperature (82°C), the closer to the raw material The glass transition temperature, the higher the transparency of blown bottles. 3 Mandrel temperature: In order to ensure a relatively uniform temperature distribution of the mandrel, the temperature of each section of the mandrel is: 45°C-55°C for the mandrel head, 40°C-50°C for the middle part, and 25°C-35° for the tail part °C. In the parison injection station, due to the high melt temperature, the temperature of the mandrel bar should be the upper limit of the above range. When the mandrel bar is transferred to the demoulding station, the temperature of the mandrel bar is the lower limit of the above range due to internal cooling. 5 blow mold temperature: Cooling bottle cooling water temperature at 5 °C -10 °C, can blow mold temperature control in the range of 10 °C -35 °C. 5 inflation pressure: bottle body blowing pressure of 1-1.2M pa, injection pressure at 60 ~ 100M pa, packing pressure to take about 80% of the injection pressure, pressure holding time should not be too long. Due to the rapid crystallization of PET, higher injection speeds are required in the production process.
4.2 Injection Molding of Polycarbonate Bottles (PC)
The injection blow molded PC bottle body is preferably an ordinary three-stage screw with a minimum aspect ratio of 15 to 1. The ratio of the transition section to the length of the metering section is taken to be 3 to 1, and when the screw diameter (D) is less than 80 mm, the pitch is taken to be 1D. . The screw head adopts a non-return structure. PC is a kind of hygroscopic polymer. Under high temperature, even if there is trace amount of moisture, it will affect the forming. Therefore, the plastic particles must be fully dried before injection molding, so that the moisture content is reduced to 0.015-0.02%. Drying conditions: At a temperature of 110-120°C for 8-12 hours, the hopper should be preheated to about 110°C and kept warm so that dry plastic particles do not rapidly cool and reabsorb moisture. PC's melt viscosity is very sensitive to changes in temperature, increase the temperature, the viscosity has decreased significantly, so the front barrel temperature at 240 °C -260 °C, in the barrel 260 °C -280 °C, after the barrel 220 °C -230 °C, The barrel temperature should not exceed 310°C. Generally, the temperature of the barrel is controlled before and after blow molding. The temperature of the parison is 260°C-280°C, the injection pressure needs high pressure injection, and the injection speed is too fast and prone to melt fracture. When blowing, the bottle body should be cooled evenly. The blowing mold temperature is 65°C-80°C. The purpose of the mold temperature increase is to reduce the temperature difference between the mold temperature and the material temperature, thereby reducing the internal stress of the bottle body. Blow pressure is generally 0.4-1.0Mpa.
4.3 Injection Molding of Polystyrene Bottles (PS)
PS is a non-crystalline plastic with high transparency. Because the PS molding temperature range is large, the thermal stability is good, the heating flow and the cooling and solidifying speed are fast, and the melt viscosity is moderate, making it easy to form. In the premise that the fluidity is guaranteed to fill the cavity, the temperature of the cylinder is low, and usually the temperature of the front cylinder is about 200° C. The temperature of the nozzle and the rear cylinder is about 40° C. lower than the temperature of the front cylinder. Injection pressure is 70-130Mpa. When the molten material fills about 95% of the cavity of the parison, the injection pressure is switched to the holding pressure, and the holding pressure takes about 80% of the injection pressure, the injection speed is higher, the injection speed is too low, and the bottle body is fused The line becomes obvious. Screw speed: The pre-molding time cannot be longer than the cooling time. Increasing the screw speed can shorten the pre-molding time. Generally, the screw speed changes gradually from slow to fast depending on the plasticizing state of the melt. The rotation speed is about 70 γ/min, the blowing mold temperature is 40°C-65°C, and the inflation pressure is 0.3-0.7Mpa.
4.4 Polypropylene (PP) Bottle Injection Blow Molding
PP is a high crystallinity plastic, and the melt flow rate of the blow molding grade PP is generally 0.5-3.0 g/10m in. When the melt index (MI) of the PP is selected to be less than 0.2 g/10m in, the front barrel temperature is 200°C to 240°C, the barrel temperature is 170°C to 220°C, and the barrel temperature is 160°C to 190°C. Injection pressure selection: PP melt fluidity is good, generally take 80-90Mpa. When the PP melt is injected into the parison mold nearly 95%, the injection pressure should be converted to hold pressure pressure, and the holding pressure is about 80% of the injection pressure. Due to the large crystallinity of PP, the molecules are organized and compact, and the intermolecular forces are strong. Reflected in the bottle body is high tensile strength, high rigidity, good gloss, and improved heat resistance, but poor flexibility and transparency. Thus the temperature of the blow mold takes the range of 30°C-60°C. PP thermal stability, improve the screw speed can quickly complete the pre-plastic, so the screw speed take 60γ/m in, the high value of the back pressure will inhibit the screw's retreat speed, preferably at 0.5M pa, inflation pressure The value is about 0.5-0.8Mpa.
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