Views:20 Author:Site Editor Publish Time: 2019-01-21 Origin:Site
The difference between injection blow molding and extrusion blow molding plastic bottles:
1 Injection blow molding and extrusion blow molding health care productplastic bottleexcing blow molding and injection blow molding plastic bottle two process is different: injection molding, the mold used to form plastic bottles should include yang and yin mold. By the injection machine under high pressure to inject the plastic melt into the mold cavity, open the mold cavity, the impotence must be removed from the yin mold, in order to top out the bottle body. In extrusion blow molding, the extruder head is formed. Blow molding mold is mainly composed of two halves of the yin mold, generally do not need the yang mold, with the injection of compressed air blowing type blank.
1.1 Extrusion blow molding characteristics of injection blowing compared to extruding, extruded blow molding characteristics are: (1) blow molding machinery (especially blow molding mold) the cost is low, such as molding the same product, blow molding machinery is about 1/3 or 1/2 of injection molding machinery, the production cost of the product is also lower. (2) In blow molding, the type blank is formed at a lower pressure by extrusion head and blowing at low pressure (mostly 0.2 to 1.0 MPa), so the residual stress of the product is small, resistant to stretching, impact, bending and environment and other strain performance is higher, with better performance. In injection blow molding, the plastic melt is used at high pressure (15 to 140 MPa) through the mold runner and gate, which leads to uneven stress distribution. (3) The molecular weight of blow-molded grade plastics (e.g. PE) is much higher than that of injection-grade plastics. In this way, blow molding products have high impact toughness and high resistance to environmental stress cracking, which is very beneficial to the production of large-capacity plastic bottles. (4) Because the blow molding mold is only composed of the negative mold, it can change the wall thickness of the bottle body by simply adjusting the head die gap or extrusion condition, which is beneficial to the product that can not accurately calculate the required wall thickness in advance. For injection molding, the cost of changing the wall thickness of the product is much higher. (5) Blow molding can be molded wall thickness is very thin products, such products can not be formed by injection method. (6) Blow molding can be molded in a complex, irregular and integral product. When using injection blow molding, Mr. to produce two or more pieces, through the buckle, solvent bonding or ultrasonic welding and other combination.
1.2 Injection blow molding characteristics Injection blow molding characteristics are: (1) plastic melt is injected into the blank mold, it is subject to a certain orientation effect in the inner cavity. In addition, the temperature of the type of billet blowing is lower than the extrusion blow molding, the orientation effect of blowing can be retained more, which helps to improve the strength of plastic bottles and other performance. (2) Plastic bottle size (especially neck thread size) high precision, more easy to ensure the uniformity of the wall thickness of the bottle body, bottle size is one. (3) The surface of the bottle body does not form a joint seam, do not need to be trimmed after molding, generally do not produce corner residual material, extrusion blow molding produced corner material is usually 5% to 30%. (4) The bottle body gloss is high, the bottle body is molded with transparent polymer is clearly transparent. (5) Blow molding mold can be set sliding bottom module, so the bottom shape of the bottle body design flexibility is greater. Better for forming rigid plastic bottles and wide-mouthed plastic bottles. (6) Note blow molding to have a type of blank mold and blow molding mold two molds, and mold requirements are high, so the injection blow molding mold cost is higher, about 2 to 3 times the extrusion blow molding. Due to the high pressure on the melt in the mold cavity (10 to 40 MPa), the residual stress of the blow-moulded bottle body is higher, and the mold force required by the type blank mold is high. Most of the bottlebody with injection molding is small (generally 10 to 300 mL), can not form a complex shape of the product, energy consumption is significantly higher. In the packaging of drugs, the degree of sealing of the bottle mouth directly affects the safety of the drug during the validity period of the drug, and the injection blow molding method is conducive to ensuring the accuracy of the bottle and thread size and appearance of the dimensional accuracy, the bottle wall thickness is uniform, adapted to the requirements of the drug packaging, can prevent the drug in the bottle from being contaminated by external substances, so the State Drug Administration as early as the "95" period proposed the use of injection blow molding method to produce high-quality pharmaceutical plastic bottles.
2 Plastic bottle form factor and physical and chemical performance detection bottle appearance detection: plastic bottle appearance testing mainly includes the overall shape of the bottle body, surface tone, gloss, appearance quality and other quality characteristics of the person's visual sense. The basis of the appearance quality inspection is based on the defects of various parts of the plastic bottle, the different appearance defect standards are worked out. The appearance quality of the bottle body is usually marked with a physical minimum allowable limit or a standard specimen, the sample is best sealed one for each defect for comparison verification. But from the overall requirements of plastic bottles, its appearance quality should be uniform and consistent milky white color, there must be no obvious color difference, the surface of the bottle should be smooth, flat, not allowed to have deformation and obvious scratches, not allowed to have sand eyes, oil, bubbles, bottle mouth should be smooth, with the cap has a good fit. Bottle body appearance size detection: due to the production of pharmaceutical plastic bottles of different degrees of precision equipment, the selection of raw materials and process parameters, the appearance of the precision will be different. Generally using the same equipment, the same raw materials and molding methods produced plastic bottles, should be stored at a temperature of 23 degrees 2 degrees in the heated room for a certain period of time before the measurement, and under stable process molding conditions, against the design of the product design map of the different parts of the reference size of the appearance measurement. Several appearance dimensions highlighted are:
(1) Plastic bottle overall height measurement: the so-called bottle body overall height size refers to the vertical distance from the mouth of the bottle to the bottom of the bottle, the test method is to place the plastic bottle on a horizontal surface, the cursor caliper - end into contact with the highest point of the bottle mouth, and then rotate the bottle body 360 degrees, read the maximum and minimum size value, and the design map size control is consistent. For example, the height-of-size error of the 40-60 mL bottle should be controlled within the range of .5 mm.
(2) Plastic bottle mouth outside the diameter size measurement: the specific measurement method is to measure the tool scale across the center of the bottle mouth, avoid the position of the bottle body fit die line, the spindle close to the mouth thread, the round bottle mouth rotation 360 degrees, measure the maximum and minimum value, and with the bottle design map, its outer diameter error should be controlled in the area of 0.1 mm of soil.
(3) Plastic bottle diameter size measurement: the measurement method is to use the cursor caliper measuring surface to contact the largest outer diameter measurement of the body of the bottle, close the cursor caliper, and then rotate the plastic bottle body 360 degrees, and record the maximum and minimum size, the error should be controlled in the range of 0.l mm.
(4) Measurement of the thickness of the wall of each part of the plastic bottle: for the medicinal plastic bottle of the circular swing body, the measuring area of the symmetrical part will be cut with a tool, so that the measuring tool can enter the test point of each part of the measurable bottle body, then the thickness of the plastic bottle mouth, shoulder thickness, body thickness, the thickness of the bottom of the bottle symmetrical parts of the strict measurement, and record the maximum and minimum value of the sample size of the sample. Physical and chemical performance test of medicinal plastic bottles: the main items of physical and chemical performance test of plastic bottles are heavy metal test, non-volatile residue test, burning residue test, reductive substance test, seal performance test, oscillation performance test, water vapor penetration test and abnormal toxicity test and bacterial culture test. The above test projects are in accordance with the yY0057-91 solid medicinal polyolefin plastic bottle standard sampling method, regular spot checks and testing, if all meet the targets of these testing items, and meet the use requirements, can ensure that the pharmaceutical plastic bottle packaging has good barrier performance, health performance, sealing and safety performance, can ensure that the drug in the validity period of non-deterioration.
3 Injection blow molding bottle body external shape size development trend Injection blow molding small and medium-sized plastic bottleneck section of the thread shape from the original trapezoidal thread (single head) to semi-circular multi-head fine thread development. The use of this bottle mouth thread form mainly considers to ensure the good matching of the bottle cap, because the moisture resistance of the drug packaging depends to a large extent on the closeness of the bottle and cap, here is to reflect whether the bottle sealing performance is good or bad main part. Plastic bottles should be loaded with a screw-cap machine that adjusts the size of the torque force to spin the cap, the torque force can be selected according to the diameter of the relevant standard root bottle cap. Ensuring the accuracy of the size of the bottle and the cap is an important prerequisite for moisture resistance, and whether the screw is tight is the key to the effect of moisture resistance. In order to ensure the safety of drug use, first of all, improve the sealing of the bottle mouth, increase the effect of moisture resistance. At present, most manufacturers in the plastic bottle mouth using aluminum foil gasket electromagnetic induction seal, greatly increased the sealing performance of the plastic bottle mouth. From the bottleneck of the round plastic bottle and the section at the shoulder of the bottle, the neck and shoulder consist of two tangented arc radius, and from the cutting point of the two-segment circular rotating body. The main factor affecting the shoulder strength of the bottle is the tilt angle of the shoulder position of the bottle, when the shoulder is too flat, the bottle body is prone to a subsidence. If the shoulder length of the bottle here is 10 mm, the shoulder tilt angle should be greater than 15 degrees, the thickness of this part should not be less than 1 mm (refers to the small bottle body), there is still a tendency to thicken, to ensure that in the packing of drugs and the use of the bottle body does not occur shoulder rupture phenomenon. If the bottle body is a circular swing body shaped in the shape of the garden column, the requirements for the bottle body is uniform wall thickness, the bottle wall is too thick will increase the weight of the bottle body, the consumption of raw materials increased, while the pressure in the bottle body increases and shrinkage will also increase. The bottle wall is too thin to blow molding and low strength, - the requirement is in addition to the bottle mouth strengthening ribs and threaded parts than the thickness of the bottle body, other parts of the wall thickness should be uniform - to. However, in order to improve the barrier and strength of plastic bottles, the design value of the bottle body in the range of l.5 to 2 mm, the current thickness towards thickening trend development. Most of the bottom of the plastic bottle is in the form of a convex or flat bottom double corner structure, because the center of the bottom of the cylinder protruding into the bottle, forming an arch, can increase the anti-internal pressure capacity of the bottle body, and ensure the stability of the bottle body. Note blow molding also avoids plastic collapse and uniform thickness of the bottom of the bottle, while the bottom structure of the flat-bottomed double-circular angle is mostly used for large volume plastic bottles, which can better withstand pressure from inside the bottle.