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BFS（Blow-Fill-Seal）Extrusion Molding

BFS technology is an advanced technology for producing the plastic-packaged preparations, by which the whole process of blowing, filling and sealing can be completed at once under a sterile environment. Compared to the conventional filling lines, it has great advantages. However, due to the complexity of such equipment, more factors will affect the product quality, in which the plastic bottle molding problem is the most prominent one.

The plastic bottle molding is affected by various factors, such as plastic performance and melting temperature, vacuum setting, compressed air pressure setting, cooling setting, equipment maintenance level, device operation motion setting parameters as well as the experience of operators. Firstly, this article aims to seek the best extruding temperature through the experiment of adjusting the temperature of the extruder so as to guarantee the quality of the plastic bottle molding. Secondly, this article details analysis on the factors causing the abnormal bottle molding and provides corresponding solutions. At last, this article provides the suggestions how to guarantee the stable operation of production, how to improve the product percent of pass and how to reduce the production cost.

Extruder Temperature Experiment

l Equipment & Materials

BFS-310 equipment manufactured by Tofflon has been adopted to conduct the contrast experiment, which can produce 30 2ml bottles at once, with the production capacity of 9000 bottles/ hour. The plastics particles selected in this experiment is 3020D low density polyethylene (LDPE) produced by BASELL, a German company.

l Experiment Method

The plastic particles are put into the hopper on top and then get melted. After that, the melted liquid goes through the screw and is pushed into the die, in which a set of 30 bottles is blow-molded. The drug liquid is transported from the preparation room to the overhead of the system through pipelines. After the empty bottles are cooled inside the die, the drug liquid is injected into the bottle through multi-head filling port, and then the bottles get sealed. After the whole process of blowing, injection and sealing have been

completed; the bottles come out from the equipment. In the process of extruding and molding, the temperature control has a significant impact on the molding process and molding quality. Through increasing the extruder’s heating temperature, it is helpful to reduce the melt’s viscosity, to improve the melt’s fluidity and reduce the power consumption of the extruder. Through increasing the screw speed, it is beneficial to improve the product’s intensity, brightness, and transparency. The main parameters of the 3020D plastic particles are shown as below:

No.	Item	Parameters
1	Manufacturer	Basell (Germany）
2	Model number	3020D
3	Density	0.928(g/cm³)
4	Melt flow rate	0.3(g/10min)
5	Sterilization temperature	106-108℃
6	Vicat softening poit	102℃
7	Melting temperature	114℃
8	Extruder temperature	160-190℃

The experiment adjusts the extruding temperature setting within the temperature range of the extruder and makes comparison in respect of the yield, bottle weight, thickness, light transmittance and the other quality indicators of the products. In the circumstance that the heating temperature of the extruder increases appropriately, the melt’s viscosity will be reduced and its fluidity will be improved. It is good for the molding. However, with the increase of the temperature, the plastic may have cross-linking reaction, which has an impact on the light transmittance. The experimental data shows that the higher extruding temperature is good for the bottle molding and the product yield coefficient. However, with the increase of the temperature setting, the light remittance of the bottle wall will be reduced. Especially, after the high temperature sterilization, the light remittance will be far lower. Therefore, through comprehensive consideration, 170℃ is an appropriate extruding temperature to get the relatively good product quality. The pass rate of light remittance under different temperature conditions as below:

Temperature	Percent of pass	Thickness（mm）	Light transmittance
165℃	98%	Min 0.494	Min 76.6%
		Max 0.561	Max 69.4%
		Ave 0.539	Ave 71.4%
170℃	99.4%	Min 0.502	Min 73.2%
		Ave 0.568	Max 68.3%
		Ave 0.545	Ave 69.5%
175℃	99.6%	Min 0.504	Min 71.0%
		Ave 0.571	Max 66.3%
		Ave 0.547	Ave 67.8%

Data on bottle shapes tested under different extruding temperatures.

Reasons for Causing Abnormal Bottle Molding and The Corresponding Solutions

From the data of the experiment results, it can be analyzed that 3020D presents the relatively data within the temperature range of 70℃~175℃. When the temperature within this range increases appropriately, the melt fluidity speed increases and the bottle wall thickness will have a slight increase correspondingly.

In the actual operations, there will be more factors to affect the bottle molding. Besides the extruding temperature, the defected bottle molding can also be related to the stability of the equipment and the operation skills of the operators. The defected bottle molding is the main problem to lower the percent of pass. Simultaneously, it is also of great importance to correctly set the equipment parameters and well grasp the technology standard. In addition, the defected bottle molding and the protective machine halt will not only reduce the yield coefficient, but also, more importantly, bring environmental risks since the human intervention will affect the aseptic conditions. The table below shows the analysis on the reasons of causing the abnormal bottle molding and provides the detailed adjustment solutions.

Abnormal item	Reason	Solution
Curving tube billet	Wrong adjustment of the throttle valve of the tube billet	Adjust the throttle valve of the tube billet
Different lengths of tube billets	Wrong adjustment of the feedstock throttle valve of the tube billet; the clearance between the die core and die sleeve are different	Adjust the feedstock throttle valve; adjust the height of the die core
Folded bottles inside the die	The tube billets are blown too large	Adjust the blowing throttle valve of the tube billet; increase the evacuation time of the tube billet.
Uneven thickness of the tube billet’s circumferential wall	The extruding die core and die sleeve are eccentric; the tube billets are blown too large and the air cannot be well exhausted.	Check and adjust the die core and die sleeve to be concentric; adjust the tube billet’ blowing and evacuation time.
Leakage of the bottle head	The parallel misalignment of the left and right diesis too large; The filling needle is dripping liquid.	Check the installment of the die and the filling needle.
Dents on the bottle wall; W strips at the bottom of the bottle	The air vent of the die is clogged	Add a vacuum hole to exhaust air; Use the texturing on the surface of the die to increase air evacuation.
Scratches inside and outside the bottle; The stripes are too prominent.	The extruding head or the discharge hole is unclean; impurities exist in the die core and die sleeve.	Clean the extruding head; Clean the discharge hole of the tube billet.
Foreign matters on the bottle wall	Foreign matters are mixed in the plastic particles; the extruding head or the discharge hole is unclean.	Check the plastic particles; clean the discharge hole of the tube billet.

In addition to the extruding system, there is another important factor to influence the percent of pass of the bottles, and that is, the die. After the extruder produced the qualified tube billet, die is the most important place for bottle molding. The bottle shape design, the temperature control, the vacuum control, the installment, and the clamping pressure control of the die will all have effect on the molding quality of the bottles.