The Basic Knowledge Of Bottle PET Bottles

- Oct 23, 2017-

PET name is Polyethylene Terephthalate, is produced by the combined after the terephthalic acid and ethylene glycol polymers, or polyester.

PET plastic has the characteristics of light weight, high transparency, high impact resistance, etc., also can prevent carbon dioxide gas, so that the soda can be kept "steam". Therefore, PET plastic is suitable for packaging, especially for water and soft drinks! Normal PET bottle production process is also made from PET polyester chip additive oil after hot melt injection bottle embryo, stored in a certain temperature humidity environment after a period of time after crystallization or not crystallization, and then made into bottles. Cover material for PP and PE, divide into two kinds, injection and molding production process and bottle making similar, but using the masterbatch, some still need side pads, covering sometimes labeled with printed logo, etc., among them the top plastic cover has a faint dot. The PET bottle is mainly used for the packaging of medicine and carbonated drinks, and can also be used for the packaging of liquor, tea, fruit juice, mineral water, edible oil, condiments, cosmetics, pesticides and detergents.

As a medicine packing container, polyester bottle has many advantages.

First of all, polyester bottles quality light, easy to form and firm.

The strength and elasticity are obviously higher than other plastic materials, which can withstand considerable impact without breakage. It is best suited as a thin, light and powerful medicine packaging bottle. After the introduction of the PET bottle in the early 1980s, the PET bottle has developed rapidly with an unshakable momentum. In just over twenty years, it has become the world's most important liquid and solid packaging container. In the case of drug packaging, the weight of the PET bottle is only about 1/10 of the glass bottle in the same volume. In the same diameter, the PET bottle has 1.5 times the capacity of the glass bottle. Use PET material to make a bottle that is transparent or opaque.

Secondly, medicinal PET bottles have good gas barrier properties.

In the commonly used plastic material, PET bottle blocks the water vapor and the oxygen performance is the best, which can completely satisfy the special storage requirements of drug packaging. PET has excellent chemical resistance and can be used for the packaging of all items except strong alkali and some organic solvents.

Thirdly, the recycling rate of PET resin is higher than that of other plastics

As a waste combustion treatment, its combustion calorific value is low and flammable, and does not produce harmful gases. Fourth, made of PET food packaging is in line with food hygiene requirements, because the PET resin is not only a harmless resin, but also a kind of pure resin without any additives, passed, including the u.s., Europe and Japan, a strict inspection of food hygiene law, is considered to be a qualified and safe medicine and food packaging materials. These advantages make pet bottles a leader in plastics.

The world's polyester output is growing at double-digit rates. The medicinal plastic bottles made from polyester are one of the most ideal packaging products in appearance, luster, physical and chemical properties and quality assurance. Pharmaceutical processing technology of polyester bottle 1, the characteristics of polyester raw materials For the bottle blow molding of raw materials for polyester (PET) of saturated linear thermoplastic polyester, main application performance is: intrinsic viscosity (IV) should be controlled in 70 ~ 85 ml/g, the blow molding bottle has high mechanical strength and transparency; For large volume (greater than 2 litres) of the bottle, the properties of polyester raw materials were selected as 70 ~ 75ml/g. It is advisable to use the material production of high quality viscosity index for injection molding medicine small volume bottle. Due to the selection of raw materials, the selection of process parameters and the quality of the bottle are related. Therefore, in the production of pharmaceutical PET bottles, the characteristics of the raw materials such as the characteristics of viscosity, crystallization temperature, cooling rate and orientation effect are particularly important. This is because the polyester material is a crystalline polymer with a very small crystallization rate, just for 6 mu m/min (Max). In this paper, the crystallization and crystallization of pet bottles can be changed by the process controlling crystallization temperature and cooling rate, and the crystal type and quantity can be changed. Polyester requires a crystallinity of about 30 per cent. In slightly higher than the glass transition temperature or slightly below the melting temperature, crystallization rate of polyester is very small, crystallization takes a long time, at about 175 temperature, crystallization time is much shorter.

In a word, the crystallization process of polyester crystallization by heating only is slow, and it is possible to form a large crystal ball, which refracts the light and makes the product white and brittle. In addition, the crystallization of pet rate reduced with the increase of its Ⅳ. The orientation can arrange the polyester molecules in order and promote the crystallization. The crystals formed are called strain induced crystals, whose grain is very small and will not refract the light. Therefore, the polyester products are transparent. If the polyester sample of some crystallization of the orientation is treated with heat setting, the samples are further crystallized and the sample is still transparent. Therefore, crystallization and orientation are the key factors that influence the performance of the tensile blow molding process. If the bottle is filled with hot filling and pasteurized treatment, some crystalline polyester is also needed to be processed to further crystallize to improve the heat resistance. 2, polyester material to wet and dry Due to the processing of polyester, containing water will react with polyester melt in the process of hydrolysis and fast consumption, namely water bubbles in the products. Hydrolysis can reduce the characteristics of polyester melt viscosity, also influence on the performance of the products and mechanical strength, and polyester raw material is hygroscopic polymer, reason should be the strict dry before processing, its residual moisture content less than 0.005%. The polyester raw material should be used to wet dry system to dry. The dry heat air provided by the drying device enters the raw material from the bottom of the hopper, and then returns the drying device after absorbing the moisture contained in the raw material. To prolong the life of the drying device to wet the bed, maintain its efficiency, to make from the hopper after wet air after cooling device (circulating water cooling can be used), the air temperature is below 65 ℃. Maintain constant temperature control of the rear cooling device to prevent overheating air from entering the wet bed. The cooled air passes through the filter to remove particles from the air. The air is removed from the wet bed to remove the moisture, and then it is heated by the heater to return to the drying hopper again. In is dry raw material conditions: the drying temperature is 140 ℃ ~ 180 ℃, the air dew point to 40 ℃, the air volume of 0.06 cubic meters/min (kg) h). The drying time is 4h. The above conditions should be noted: (1) when the air volume is higher than 0.06 m3 / min(kg. H), the operating range can be widened to reduce the drying temperature and the energy consumption will be too high. (2) it is important to ensure dry dew point as low as possible, but low dew point - 10 ℃ when there will be no problem; However, the air dew point should be strictly monitored. When it is too high, it should be reduced in time. (3) the drying temperature was one of the key parameters, can be dry in a variety of temperature and measure the characteristics of the parison viscosity to determine the best drying temperature, the average is 150 ℃ ~ 163 ℃. Downtime, the drying temperature should be down to about 120 ℃. (4) drying time longer will reduce the intrinsic viscosity of polyester raw materials, reasonable control drying temperature become the key parameters, raise temperature slightly will results in the decrease of the characteristics of the polyester viscosity have bigger, so the drying time should be as short as possible, in order to broaden the scope of operation. In the process of drying, due to the high temperature drying polyester, hopper devices must have the good heat insulation performance and using glass fiber for the thermal insulation layer, should avoid dry polyester raw material contact with outside air, because of polyester raw materials can quickly absorb moisture in the air. For example, completely dry polyester raw material with relative humidity is 35% ~ 40% air contact 12min, moisture content is 0.005%. The molding method of the polyester bottle is made of extrusion blow molding and injection blow molding. There is a one-step method and two steps for stretching and blowing. In a one-step process, the forming, cooling, heating, stretching, blowing and the extraction of the moulds are completed in sequence on one machine. The two-step principle adopts extruding or injection molding type blank, and the blank is cooled to room temperature, becomes the semi-finished product, then reheating the type billet and becoming the bottle body in the stretching and blowing machine. The forming, stretching and blow molding of the type billet are completed on two machines. A one-step injection molding PET bottle, the injection equipment requires two sets of molds, namely injection mold and blow moulds. And the injection mold is mainly composed of mold cavity and mandrel bar, and the correct selection of the size parameters of each part is the key to the shape of the bottle. Therefore, it is necessary to combine the mould size parameters with the molding process to make a reasonable selection. 1. The ratio between the height of the PET bottle and the diameter of the neck thread can be determined that the length of the diameter ratio (L/D) diameter ratio of the core rod is not more than 10:1. This is because the core rod is the cantilever beam in the mold, and it is subjected to high injection pressure when filling the mold. When the diameter ratio is larger than the selected value, the core rod is more curved, and it is easy to cause the blank and wall thickness distribution. However, through the procedure to control the filling speed of the melt, or in the process of filling the core with a sliding thimble to make the core rod pair, the length of the core rod is larger than that of the core rod. The height of the type blank is the height of the reference bottle and the height of the height coefficient, which is generally 92% ~ 95% of the height of the bottle body. In order to ensure the bottles have good transparency, the melt filling the parison after mold, rapid temperature fell to below 145 ℃, but better than polyester material of high glass transition temperature (82 ℃), and the closer it gets to the glass transition temperature, the transparency of blow molding bottle. Parison mould cooling water temperature as low as 10 ℃ ~ 35 ℃, in order to fast cooling parison, also take liquid or gas to the mandrel continuous cooling, including air conditioning can make the mandrel is more uniform temperature distribution, the air pressure usually around 1 mpa. 2. The melt temperature of melt temperature is one of the important parameters to be paid attention to. Considering the equipment, the screw design has a great influence on PET melting, mixing uniformity and melt temperature. The PET injection should be low cut, low compression ratio (about 2/1), the feed length is longer, and the transition section and the metering section are shorter. The temperature of the cylinder of the device has a great influence on the melt temperature, and the temperature of the cylinder will decrease the viscosity of the PET melt. The temperature of the cylinder has obvious influence on the transparency of the blank, and the temperature of the cylinder can improve the transparency of the blank. When the barrel temperature is 280 ℃, for example, the corresponding melt temperature is 290 ℃, can ensure transparency of the parison is best. The further improvement of cylinder temperature does not improve the transparency. When the cylinder temperature is low, it is necessary to raise the speed of the screw rod to the temperature of the outlet, and to improve the transparency of the blank. However, due to the short time of the melt through the hot runner system, the temperature of the melt is relatively small. Increase injection pressure, that is, when the injection rate is injected, the melt will produce higher shear heat through the nozzle, which will obviously improve the melt temperature, so that it can be formed when the cylinder temperature is lower. When the pressure pressure is high, the crystallization rate of the melt in the mold of the mold will be reduced, and the transparency of the blank will be reduced, especially when the cylinder temperature is low. In the actual production process, for a given polyester resin and molding equipment, it can be to determine the appropriate melt temperature: first, gradually reduce the temperature, began to the parison fog, and then raise the temperature, just reached the transparent type forming temperature, as appropriate melt temperature. It contains acetaldehyde, which is used in injection moulding, which makes it easy to chemically react to packaged drugs, especially liquid medicines. Therefore, it is necessary to control the formaldehyde content of billet, which is less than 10 parts per million. The reduction of acetaldehyde content in a bottle is an important subject for the optimization of the production process of polyester bottles, and the acetaldehyde content of the form is related to the temperature and duration of the melt. Melt temperature is below 265 ℃, acetaldehyde content and a linear relationship with time; Melt temperature higher than 265 ℃, the exponential relationship between both. Because of acetaldehyde content in the parison and barrel temperature increase linearly, branch pipe and gate temperature rise will also be a small increase in acetaldehyde content, but improve the flow temperature, the increase of the content of acetaldehyde is small, this is because the melt through the hot runner system time than their short stay in the barrel. The rotation speed of the device has no effect on the acetaldehyde content in the billet at lower value, but when the rotational speed is further improved, the resulting shear heat will increase the melt temperature and increase the content of acetaldehyde. Increasing the back pressure increases the melt temperature, thus increasing the content of acetaldehyde. Therefore, the back pressure should be reduced as far as possible in the premise that the polyester raw material is plasticized evenly. To improve the melt temperature, injection pressure increased but due to time is shorter, the melt through the nozzle so that only a small amount of acetaldehyde content increased, and the holding type pressure and mould temperature has no effect on acetaldehyde content. It can be seen that the temperature of the cylinder has obvious influence on the acetaldehyde content of the polyester slab, and the influence of screw speed, injection rate, back pressure and heat flux temperature on acetaldehyde content is small. Therefore, it is possible to improve the injection rate and reduce the temperature of the cylinder. High injection pressure is used in the initial time of filling, to stabilize the filling process and then inject with low pressure, which can achieve better results. Therefore, the polyester type forming, selection of melt temperature should be appropriate, to ensure transparency of the parison, and also can control the production of acetaldehyde, the melt temperature about 280 ℃. 3. In the process of molding process, the main axial stretch of the billet is when the injection molding billet is injected with the value of the bottle to blow up the small volume of the polyester bottle. The smaller the axial tensile, blowing ratio (refers to the ratio of the parison diameter) and the diameter of the bottle, the greater the bottle of the greater the likelihood of uneven distribution of wall thickness, easy to cause the bottle shoulders with the bottle or bottle and bottle the curve of the transition area between parts, uneven wall thickness. The volume of the small volume bottle is 1.5 ~ 1.8. In the case of the ellipse, the ratio of the ellipse to the length of the ellipse is less than 1.5:1, the circular shape of the circular shape is adopted. When the ellipse ratio is less than 2:1, the transverse section can be used to form the circular core and oval shape. When the elliptical ratio is greater than 2:1, the mandrel and mold cavity are generally designed to be oval. The design difficulty and manufacturing cost of the mould are higher than the increase of the elliptical ratio, which should not exceed 3:1. 4. The diameter and thread size of the billet and neck size of the injection mold shall be uniform with the size of the bottle mouth, and can be matched with the thread size of the bottle cap. Because there is no uniform national standard for this, the size of the bottle mouth is determined according to the contents of the bottle. Determine the parison neck size and blow molding mold cavity size, the bottle should also be considered after molding shrinkage, PET bottle blowing air pressure in the parison is 1.2 MPa, the 5 ~ 10 ℃ cooling water cooling blow molding mold, rapid cooling after the parison huff. 5, the bottle injection molding core functionality Injection blow molding of mandrel used function mainly has five aspects: (1) to determine the shape of the shape of the parison with the inner diameter of the bottle neck (2) in the process of mechanical transfer away parison or bottles; (3) the inner rod is equipped with airway and air outlet, conveying compressed air to blow out the billet; (4) the inner rod can circulate liquid or air to adjust the temperature of the blank; (5) the mandrel tail place close to the fitting surface open 0.10 mm deep grooves, the parison end into the slot wedge, avoid from the indexing of parison forming to the process of blow molding station, parison neck screw dislocation caused by the elastic contraction. The groove ACTS as a seal to reduce the leakage of compressed air during blowing. 6. The length and diameter of the core rod length and diameter are determined by the type blank. The diameter of the core rod is smaller than the inner diameter of the bottle body, which makes it easy to remove the bottle body. But the diameter of the core rod should be as large as possible within the neck of the bottleneck, so as to avoid excessive inflating ratio. The coaxial degree should be in the diameter of 0.05 ~ 0.08 mm. The diameter of the core rod of the bottle mouth is determined by the diameter of the bottle mouth and the thickness of the bottle mouth. The range is generally the diameter of the bottle mouth is equal to the diameter of the top of the bottle and the thickness of the bottle mouth. 7, at the bottom of the mandrel and the determination of distance between the bottom of the parison dimension The distance to the bottom of the parison thickness size, its size value is reasonable or not, directly affect the thickness is in accordance with the requirements of the bottom of the bottle. The general calculation method is: the thickness of the bottom of the blank (B) is equal to the minimum thickness (T) of the bottom of the bottle and the weight of the bottle 0.1 times. The material used in the core rod is alloy tool steel, the hardness is hrc52-54, which is slightly lower than the hardness of the die collar. The core surface of the contact with the melt should be polished along the flow direction of the melt, and plated hard chromium to make it easy to melt the mold and mold. In the blow molding and demolation station of PET bottle, the gas continues to flow in the core bar to ensure that the core rod has a consistent temperature distribution. Temperature values of mandrel paragraphs are as follows: the head (corresponding to the parison neck) take 45 ℃ ~ 55 ℃, central (body) in 40 ℃ to 50 ℃, the tail take 23 ℃ ~ 35 ℃. In the blank injection station, the temperature of the core rod is at the upper limit of the above range due to the high temperature of the melt. The temperature of the core rod to the die position is lowered to the lower limit due to the cold. After the ejector is out of the mould, the head of the core is cooled from the outside to reduce the core temperature. 8, PET bottle injection blow molding process parameter selection in PET bottles to control the melt temperature, injection blow molding to make it at 275 ℃ ~ 285 ℃ range, high temperature than most polymer injection blow molding grade about 50 ℃. The hot runner system should adopt streamline and symmetrical design to avoid dead Angle. The nozzle shall be closed with a closed structure, and the outer surface shall be heated. In order to ensure the parison with high transparency, the melt filling the parison molds to rapid cooling after below 145 ℃, but than their high glass transition temperature (82 ℃), and the closer it gets to the glass transition temperature, the transparency of blow molding bottle, can broaden the range of work. Parison mould cooling water temperature as low as 10 ℃ ~ 35 ℃, in a quick cooling parison. The core rod can be continuously cooled by liquid or gas. The air cooling can provide a more consistent temperature distribution to the core rod shaft, and there is no leakage problem. The cold air pressure in the mandrel is usually 1MPa. It is better to use liquid, gas combined cooling mode, and the air pressure of PET billet is about 1.2mpa. The cooling water temperature is 5 ℃ to 10 ℃. With cooling blow molding tool, it can also be fast cooling after blowing.