With the rapid development of the hollow blow molding product processing industry, the traditional technology of hollow blow molding chemical barrel is difficult to adapt from the material formula, mold, equipment, and process.

In particular, chemical barrels are difficult to meet the drop requirements of dangerous goods packaging of product manufacturers: the ring position is easily embrittled by the contents, resulting in leakage or rupture.

Facing the financial storm, the hollow blow molding packaging industry has also been hit by an unprecedented economic impact. Enterprises must get out of the predicament, and industry technology must accelerate innovation, improve product quality, and reduce detail costs to overcome difficulties.

Today, Yankang summarizes the technology and practical experience of chemical barrel blow molding machines, hoping to help everyone.

A hollow blow molding machine forms the plastic double-ring barrel, and the blanks injected by the material storage and servo-controlled head are formed through equipment, molds, and blowing comprehensive processes. It has ring-shaped characteristics and a press edge hollow blow molding double-ring barrel.

1. Classification of plastic single and double-ring barrels (chemical barrels)

① Chemical barrels-single ring barrels

Hollow blow-molded barrels with a pressure ring and a pressure edge structure at the connection between the barrel mouth and the barrel body. Such as: 200L, 160L, 125L, 120L, 100L, 60L, 50L, 30L, 25L and other iron hoop barrels.
Single-ring barrels are generally open barrels, requiring a smaller pressure ring and a smooth appearance of the pressure edge solid core.

② Chemical barrels-double ring barrels

Double ring barrels are hollow blow-molded barrels with pressure rings and a pressure edge structure at the connection between the upper and lower end faces and the barrel body. Such as: 100L, 200L, 230L, and other double-ring barrels.
Double-ring barrels are generally closed barrels, requiring a larger, uniform, solid pressure ring, a smooth pressure edge appearance, and no bubbles. Qualified double-ring barrels need to meet the relevant ring drop standards.

Technical update and practical experience of hollow blow-molded double-ring barrels-Qingdao Junkang

2. Technical improvement and innovation of blow-molded chemical barrels

The quality of chemical barrels is largely determined by the quality of the pressure ring of chemical barrels.
To improve the quality of blow-molded chemical barrels, it is necessary to improve the quality of the pressure ring of chemical barrels.
It can be optimized from the following points:

a. Materials and formulas for blow-molded chemical barrels

Using high molecular-weight polyethylene alone, or mixing high molecular-weight polyethylene from different manufacturers or high-density polyethylene with similar molecular weight in appropriate proportions, the effect is better.
High molecular weight polyethylene has good rigidity and toughness and is highly resistant to oil, acid, and alkali.
In the process of batching, the matching of returned materials must be strictly controlled, and the proportion of returned materials in the batching should not be greater than one-third.

b. Mold structure of chemical barrels

① Select steel with good hardness and high wear resistance as the material for the mold pressure ring position;

② The active part of the pressure ring is a vertical structure;

③ The pressure ring stroke cannot be too long or too short.
The pressure ring stroke of the pressure ring barrel mold with a single ring structure is generally about 35mm.
The bottom ring pressing stroke of the double-ring barrel mold is generally about 55mm, and the cover ring pressing stroke is generally about 70mm;

④ The drainage structure of the barrel mouth of the double-ring barrel mold is staggered from the barrel mouth joint line, and the single-side single-groove drainage structure is changed to a double-groove drainage structure, which can make the wall thickness distribution more uniform, reduce internal stress, and prevent stress cracking;

⑤ The bottom ring edge of the double-ring barrel mold is a semi-arc structure and should be changed to a full-arc structure. When the parison is blown and formed, the wall thickness distribution is more uniform, and the internal stress is reduced to prevent stress cracking;

⑥ The outer r angle of the cover edge of the chemical barrel mold is appropriately reduced.
It is generally about 60 degrees, and it is better to change it to about 45 degrees, which has the effect of easy molding of the pressure ring;

⑦ The water transport structure of the barrel mouth of the mold should be good to prevent stress cracking caused by poor cooling.

3. The mold of the chemical barrels blow molding machine is changed to axial and radial bidirectional wall thickness control

Take the chemical barrel as an example. During the production process, the original blow molding machine usually only has the axial wall thickness control function. The rings on both sides of the parting line of the product are large, and the rings on both sides of the non-parting line are small. This is because the parison at the parting line ring is bonded and difficult to disperse, and the wall thickness here is much greater than the wall thickness at the non-parting line ring.

To optimize the quality of the press ring, the size of the press ring must be balanced first. The eccentricity can be trimmed at the position where the wall thickness of the head core mold needs to be increased, or the radial and axial servo wall thickness control system invented by the blow molding machine manufacturer can be used to fill the gap in the radial wall thickness control. The latter has a better control effect, but the cost is relatively high.
The axial and radial bidirectional wall thickness control can achieve the same size as the press ring around the ring.

4. Adjustment of chemical barrels blow molding process

① The plasticizing temperature of high molecular polyethylene is generally between 190 and 220℃;

② The air pressure is generally controlled between 0.6 and 0.8M pa;

③ The wall thickness of the ring should be sufficient;

④ The injection speed should not be too fast or too slow;

⑤ The clamping speed and low-pressure blowing time are matched and controlled;

⑥ The ring pressing speed and the ring pressing time are matched and controlled, and the faster the ring pressing speed is, the better;

⑦ The ring cooling should be good;

⑧ Maintain the stability of the equipment.

In the technology field, there will always be new problems, and there will always be new technologies to solve them.

So today, Yankang discusses the technical updates of chemical barrel blow molding machines from four aspects: materials, molds, equipment, and processes, hoping to be helpful to hollow blow molding chemical barrel manufacturers and blow molding machine factories.