Introduction to the principle and manufacturing process of medicinal plastic bottle blow molding

2023-10-25 15:21

The "injection-blow" molding process originated in the early 1950s. The application of foreign polyolefin (HDPE, PP) pharmaceutical plastic bottles dates back to the 1970s.


Related equipment research and manufacturing manufacturers include Germany, Japan, the United States, Italy and other countries. The main models are all one-step and three-station. The United States and Japan use vertical screw structures, and Germany and Italy use horizontal screw structures.


Common production processes and raw material selection for medicinal plastic bottles

1. Production process

(1) "Extrusion-blowmoulding", also known as hollow extrusion blow molding.

The extruder continuously extrudes the hollow tube, cut it into small sections with scissors (manual) or cutting device (automatic), and then move it to the extrusion blow mold for blow molding.


Advantages: simple equipment, small investment, and low cost.


Disadvantages: The bottle mouth is uneven and the seal is poor. LDPE is usually used as the raw material, and its barrier performance is much lower than that of HDPE/PP, and the shelf life of the charge is short.


 medicinal plastic bottle


(2) Two steps injection-blowmoulding.

"Injection and blow molding" are performed separately by two independent machines, commonly known as the "two-step method".

The first step: Inject the tube blank by an ordinary injection molding machine, and the bottle head part of the tube blank (bottle mouth, thread) has been formed;

Step 2: Manually place the tube blank on a honeycomb heater or an automatic circulating heating conveyor belt to heat and adjust the temperature, and then move it to the bottle blowing machine to blow into shape with compressed air.


Advantages: The equipment is simpler and the investment is less. The bottle mouth is relatively flat and well sealed. The variety development is fast, the mold cost is low, and the cost price is medium to low.


Disadvantages: Injection tube blanks and blow molding are carried out step by step, easy to transmit contamination, difficult to ensure bacterial inspection, poor product identity, not suitable for mass production.


(3) One-step injection-blowmoulding.

"Injection and blow molding" are completed on the same machine.

Different machine types are divided into three-station and two-station "injection-blow".

The three stations of the "injection-blow" bottle making machine are distributed in an equilateral triangle at an angle of 120°. The first station is the injection molding station, the second station is the blow molding station, and the third station is Bottle removal station.


The three stations can run at the same time, with high production efficiency and short cycle. It can also be connected to the conveyor belt for automatic counting and packaging, truly achieving "no contact" with human hands during the entire production process of medicinal plastic bottles, ensuring that the products are hygienic and clean.


The two stations of the two-station "injection-blow" plastic machine can be arranged up, down or front to back.

The first station is an injection molding station, and the second station is a blow molding station. Since there is one less dedicated bottle removal and cooling station, it is difficult to achieve fully automatic counting and packaging (usually manual counting in bulk). In addition, the production cycle is longer and the production efficiency is lower than that of the three-station machine.


Advantage:

High degree of automation and high production capacity. The bottle mouth has high flatness and excellent sealing. HDPE/PP raw materials are selected, the bottle wall is uniform, the barrier performance is excellent, and the filling has a long shelf life. At present, domestic standardized pharmaceutical package companies basically use one-step "injection blowing" process equipment, among which the "three-station" structure is the main one.


Shortcoming:

The equipment investment is large, the mold is complex, and the system configuration requirements are high. Not very suitable for small variety and small batch production. However, mass production can achieve high quality at low cost and good economic benefits.


 medicinal plastic bottle


2. Commonly used plastic raw materials

Solid drug packaging should use HDPE/PP and polyolefin plastic containers produced by the one-step "injection-blow" process; liquid drug filling should be used.

Plastic containers produced by PET/PP "injection-pull-blow" process.


(3) Colorants and processing aids

Titanium dioxide tio2 (anatase type or rutile type) is usually used as colorant in medicine bottles, with tio2 content 98%wt, and the addition amount is 1.0~1.5%wt. Commonly used processing aids include lubricant zinc stearate and polyethylene wax. They are all white powders, and the added amount is 0.1~1%wt.


In recent years, in order to meet GMP and 100,000-level purification requirements, tio2, zinc stearate, polyethylene wax and LDPE (high m·i) are generally mixed together to make a concentrated masterbatch, which can greatly reduce dust pollution during the production process. . A typical tio2 masterbatch formula consists of: tio2 (special grade) 60%, zinc stearate 8%, polyethylene wax 10%, LDPE 22%.

HDPE and PP are more suitable materials for solid drug packaging. They have excellent water vapor permeability resistance and can effectively prevent drugs from absorbing moisture and deteriorating. However, drugs that are prone to oxidation and deterioration should be used with caution. LDPE has extremely poor oxygen barrier properties and is not suitable for producing pharmaceutical plastic bottles, let alone filling drugs with long storage periods.

PET has excellent barrier properties to water and oxygen, and has a transparent appearance. It is an ideal choice for filling liquid drugs (syrups, oral liquids).


3. Injection-blowmolding equipment and molds for medicinal plastic containers

The structure includes: injection mold (preliminary mold), blow mold (forming mold), mold mandrel (three groups in total), hot runner, sub-nozzle, bottle removal pallet, and mandrel holder.

Mold material, thermal expansion coefficient, surface finish, processing technology and precision, design level, debugging experience, especially the control of injection mold temperature, all have an impact on the quality of the final medicine bottle product.


4. System design

The impact of system design and supporting devices on the efficiency of the "injection-blow" assembly line should be taken very seriously.


In addition to selecting "injection-blow" molding machines with reliable performance and "injection-blow" molds with precise quality, pharmaceutical plastic bottle manufacturers must carry out systematic design and planning of corresponding GMP specifications and process flows. The main contents include:


 bottle blow molding


(1). Central air conditioning system

(GMP standard factory building, 100,000-level purification, gb/t16292-16294-1996)

Main indicators: cleanliness level 100,000, three-level filtration (fine, medium and high), top feeding and side return method.

The number of air changes is 20 times/hr, and the temperature is t=26~28


(2). Chilled water system

Temperature t=5°~15°, pressure p0.2mpa, flow qrated value


(3). Cooling water system

Temperature t28°, pressure p0.2mpa, flow qrated value, spray and circulation system


(4). Compressed air system

Pressure p1.0mpa, flow rate qcalibrated value, equipped with pressure stabilizing tank, freeze dryer, secondary filtration (40μ, 5μ), automatic drain valve, compressed air temperature 65°<20.


(5). Mold temperature controller

Water medium mold temperature controller: working temperature tmax120, p0.4mpa, controlled by microprocessor or pid;


Oil medium mold temperature controller: working temperature tmax=30-300, p0.2mpa, pid or one-time control instrument


Recommendation: Use a water medium mold temperature machine to produce medicinal plastic bottles to ensure the quality of the medicine bottles and prevent oil medium leakage and contamination.


(6). Mixing, feeding and crushing devices

The mixing time is controllable (timer), and the best mixing effect cannot be achieved if it is too long or too short.


The feeding method is recommended to use top-level feeding or automatic vacuum suction. However, concentrated masterbatch coloring should be used to prevent excessive dust pollution in the workshop.


The crusher should use a low-noise, high-efficiency rotary cutter (mainly crushing bottle caps, injection molding runner material racks and a small amount of waste bottles), and the amount of recycled material should be reasonable and appropriate (less than 15%wt) to prevent the impact of repeated cycle degradation. performance. Raw materials of different brands must be processed separately (generally, resin for bottles m·i1.0, resin for caps m·i>5) and cannot be mixed at will.


 medicinal plastic bottle blow molding


5. The production of medicinal plastic bottles should be based on their specific properties:


1. Use the "injection-blow" process to ensure bottle mouth smoothness, high density, and excellent sealing and permeability, thereby ensuring the stability of the charge and extending the storage shelf life.


2. Use a one-step three-station "injection-blow" molding machine and precision mold to ensure product accuracy, thereby achieving the goals of high quality, high productivity, high efficiency, low cost, and quick return on investment.


3. System design (GMP, process flow, chilled water system, cooling water system, compressed air refrigeration and purification system, electrical system, auxiliary equipment) is a very important link and is also a necessary condition for the stable production and development of pharmaceutical package companies.


Conclusion

The production of pharmaceutical plastic bottles is a complex and important process, and in addition to advanced machinery and materials, suppliers also need to prioritize system design and adhere to GMP specifications. The result is a method for the pharmaceutical industry to create containers with smooth mouths, high-density structures, and excellent sealing and permeability.


FAQs


1. What is "injection-blow" molding?

"Injection-blow" molding is a manufacturing process that originated in the 1950s, widely used for producing hollow plastic containers, especially in pharmaceutical applications.


2. What are the advantages of the one-step "injection-blow" process for medicinal bottles?

The one-step "injection-blow" process provides high automation, excellent bottle mouth flatness, sealing, and uses high-density polyethylene (HDPE) or polypropylene (PP) materials, offering uniform bottle walls and superior barrier properties, ensuring long shelf life for pharmaceuticals.


3. What materials are suitable for solid and liquid drug packaging?

Solid drug packaging should use HDPE or PP containers produced through the one-step "injection-blow" process.

Liquid drug packaging is best suited to PET or PP containers manufactured using the "injection-pull-blow" process.


4. How should pharmaceutical manufacturers handle colorants and processing aids in bottle production?

Titanium dioxide (tio2) is commonly used as a colorant in medicinal plastic bottles, with tio2 content 98%wt. Processing aids, like lubricant zinc stearate and polyethylene wax, are added to masterbatch to reduce dust pollution and enhance production efficiency.


5. What system design considerations are crucial for efficient "injection-blow" assembly lines?

Components like central air conditioning, chilled water, cooling water, compressed air, mold temperature control, and material handling systems are critical for the production of pharmaceutical plastic bottles.