Plastic hollow container production process, equipment and development (2)

1. equipment

With the continuous advancement of technology and the scale of production, PET bottle blowing machines have become more and more automated, from the production of thousands of bottles per hour to the production of tens of thousands of bottles per hour. The operation has also evolved from the manual buttons of the past to the current all-electric computer control, which greatly reduces the difficulty of process operations and increases the stability of the process. At present, the manufacturers of injection blow blowing equipment mainly include SIDEL in France and KRONES in Germany. Although different manufacturers, but the principle of their equipment is similar, generally include the billet system, heating system, bottle blowing systems, control systems and auxiliary machines.

2. Blow molding process

PET bottle blow molding process. Important factors affecting the blowing process of PET bottles include preforms, heating, pre-blowing, molds, and the environment.

(1) preform

When the equipment blows plastic bottles, the PET bottles are first injection-molded into preforms, which requires that the ratio of the two recycled materials not exceed (5%), the number of recycling cannot exceed two, and the molecular weight and viscosity cannot be too low. Injection molded preforms need to be stored for more than 48 hours before they can be used. The unused preforms after heating must be reheated for 48 hours. The preforms must not be stored for more than six months.

The merits and demerits of preforms depend to a large extent on the merits of the PET material. The materials that are easy to inflate and easy to set should be selected, and a reasonable preform molding process should be established. Experiments show that the same viscosity of PET preforms, the imported raw materials than domestic materials easy to blow molding, and the same batch of preforms, the production date is different, the blow molding process may also have greater differences. The quality of the preform determines the ease of the blow-molding process. The requirements for the preform are pure, transparent, free of impurities, no color, and the length of the injection spot and the surrounding halo are appropriate.

(2) Heating

The heating of the preform is accomplished by heating the oven. The temperature is set manually and automatically adjusted. In the oven, far-infrared rays are emitted from the far-infrared lamp to radiantly heat the preform. The oven bottom step fan performs thermal cycling to make the temperature inside the oven uniform. The preform is rotated while moving forward in the oven so that the preform is heated evenly.

The arrangement of the lamps in the oven is generally "zone" shaped from top to bottom, with less in the middle. The heat of the oven is controlled by the number of lamps turned on, the overall temperature setting, the power of the oven, and the heating ratio of each section. The opening of the lamp should be adjusted in conjunction with the pre-blowing. To make the oven work better, the adjustment of its height, cooling plate, etc. is very important. If the improper adjustment is used for blow molding, the bottle mouth (big mouth), hard head and neck (the neck material cannot be pulled open), etc. .

(3) Pre-blowing

Pre-blowing is a very important step in the two-step blow-molding process. It refers to the fact that during the blow-molding process, the pre-blowing is started at the same time as the draw is reduced, so that the preform takes shape. The pre-blowing position, pre-blowing pressure and blowing flow in this process are three important process factors.

The quality of the pre-blow shape determines the ease of the blow molding process and the performance of the bottle. The normal pre-blowing shape is spindle-shaped, and the abnormal ones are sub-bell-shaped, handle-like, etc. The causes of abnormal conditions include improper local heating, insufficient pre-blowing pressure or insufficient air flow, and the size of the pre-blowing bottle depends on the size of the bottle. Pre-blowing pressure and pre-blowing position. In the production, it is necessary to maintain the same size and shape of all pre-blowed bottles in the entire equipment. If there are differences to find specific reasons, the heating or pre-blowing process may be adjusted according to the pre-blowing conditions. The size of the pre-blowing pressure varies with the specifications of the bottle and the capacity of the equipment. Generally, the capacity is large, the pre-blowing pressure is small, the equipment production capacity is high, and the pre-blowing pressure is high. Even if the same device is used to produce the same size bottle, the required pre-blowing pressure is not the same due to the difference in the performance of the PET material. Glass fiber reinforced PET material, the smaller the pre-blowing pressure can make the bottom of the bottle the correct orientation of the molecules, and other improper use of materials or molding process is not appropriate for the preform, there is a lot of stress concentration near the injection point is not easy to fade, if Blow molding often breaks at the injection point or bursts or leaks from the injection point during the stress test. According to the orientation conditions, the lamp can be removed as shown by 2-3 branches above the injection point to open, giving sufficient heating at the injection point to provide enough heat to promote its rapid orientation. For preforms that have been heated for secondary use or preforms that have been stored for an excessive amount of time, the molding process is similar due to the equal temperature difference effect. Compared with normal preforms, less heat is required and the pre-blowing pressure may be appropriate. reduce.

(4) Auxiliary machine and mould

Auxiliary equipment mainly refers to the equipment that maintains the constant temperature of the mold. The constant temperature of the mold plays an important role in maintaining the stability of the product. The bottle body temperature is generally high and the bottle temperature is low. For cold bottles, because the lower cooling effect determines the degree of molecular orientation, it is better to control the temperature at 5-8°C, and the temperature in the lower part of the bottle is much higher. Mold is an important factor affecting the blowing process of PET bottles. The shape of the mold will reduce or increase the difficulty of process adjustment. For example, stiffening ribs, the curvature of the transitional area, and the cooling of the lower part all affect the process adjustment.

(5) Environment

The quality of the production environment also has a great influence on the process adjustment. The constant conditions can maintain the stability of the process and the stability of the product. Blow molding of PET bottles is generally preferred at room temperature and low temperature.

3. Other requirements

A pressure bottle should meet the requirements of stress test and pressure test at the same time. The stress test is to prevent the degradation of the molecular chains during the contact between the bottle and the lubricant (alkaline) during the filling of the PET bottle and cracks and leakages occur. The pressure test is to prevent the bottle from being filled. Quality control by bursting after entering a certain pressure gas. To meet these two requirements, the center point thickness must be controlled within a certain range. In general, the center point is thin, the stress test is good, the pressure resistance is poor, the center point is thick, the pressure resistance test is good, and the stress test is poor. Of course, the results of the stress test also have a great relationship with the accumulation of material in the transition zone around the center point, which should be adjusted based on actual experience.

The adjustment of the PET bottle blow molding process is performed on the corresponding materials. If the materials are not good, the requirements for the process are very severe, and it is even difficult to blow out qualified bottles.

Automatic Injection Blowing Blow Molding Machine Series Application Range: This machine adopts injection blow molding process to blow bottle blowers that can form hollow containers at a time. It can produce high-grade containers with high bottleneck precision. Can be widely used in the manufacture of pharmaceutical, food, cosmetics and chemical industry packaging bottles.

The main technical features:

1. The bottleneck adopts high-pressure injection molding. The precision of the bottle mouth, bottle neck and upper thread are high, the product specifications are uniform, and the appearance is smooth and clean.
2. The mold closing and mold opening adopts a fast and slow motion. The high pressure mold clamping adopts the accumulator direct pressure, pressure and high productivity.
3. Horizontal three-position rotary device, large rotary table, one mold and multiple cavity molding, high productivity.
4. Product demoulding automation, flame processing automation and counting packaging automation, the organic combination of the three, can ensure that the goods from pollution, to meet the health requirements of the food and pharmaceutical industry.
5. There is no pulling and inserting action in the electrical and pneumatic systems. Appropriately adding accessories and using three molds can form deeper bottomed products.
6. With low pressure mold protection system, mandrel electrical protection system and safe operation protection system.
7. Mechanical, hydraulic and electrical systems are equipped with adjustable links to meet the technical requirements of different products.
8. The raw material has strong adaptability and can form most thermoplastic plastics, such as PE, PP, PS and so on.