Why is the most popular OPP plastic bottle not loo

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Opp plastic bottle Outlook: why not

you may have heard before that stretched polypropylene (OPP) bottles will make a grand debut and replace glass, pet and PVC in a wide range of food and non food containers. However, the predicted breakthrough did not come as scheduled. Of course, PP is cheaper and more heat-resistant than pet, but it also has low hardness, poor transparency and barrier properties, and is difficult to process. In particular, the low processing speed makes OPP economically impossible. Now, the market's interest in OPP bottles and cans has increased again, and the discussion on the long-awaited breakthrough is endless. The hard OPP containers made by the one-step injection stretch blow molding and two-step reheat stretch blow molding machines are once again claimed to be a good opportunity to transform the cost of packaging water, fruit juice, hot filled food, dry powder and personal care products

surendra agarawal, head of food R & D at Kraft, said: we look forward to a gradual change in the manufacturing cost of OPP bottles. Compared with glass, OPP bottles are lighter, harder to break and easier to grasp by hand

bottle grade PET has a density of 1.35 g/cc and now sells at 63 ¢/lb, while the transparent PP copolymer used in stretch bottles is about 0.910 g/cc and 56 ¢/lb respectively. This makes OPP bottles 40% cheaper than PET bottles under the same volume. Agarawal also pointed out that OPP bottles are lighter than PET bottles, and the actual transparency is equal to PET bottles

in 2002, about 57billion PET bottles were used in North America. The high output rotary reheat stretch blow molding machine can blow 60000 bottles per hour. In contrast, OPP bottles are currently limited to such narrow application space as infant nutrition products and medicine bottles, mainly in Asia and South America. They are mainly made on the one-step injection, drawing and blowing device. This method can not make a difference in the large amount of U.S. packaging market. Many people in the industry doubt whether the output of PP preforms and OPP bottles can match that of pet

overcome OPP defects

up to now, the disadvantages in processing speed and physical properties compared with pet have hindered the development of OPP bottles. However, PP supporters believe that these shortcomings are being overcome through advanced equipment, better bottle blank and bottle tool design, and PP resin and additives tailored for bottles

our research shows that using high-yield equipment and properly designed PP preforms and OPP bottles, it is possible to compete with PET in terms of yield, transparency, hardness, toughness and sensory properties. Said Robert Portnoy, a market developer at ExxonMobil. He believes that when OPP bottles are produced on high-speed rotary reheat stretch blow molding machines, such as those produced by Sidel, SIG corpoplast and other companies, OPP bottles are very competitive. However, the suppliers of competitive equipment point out that the one-step injection, drawing and blowing machine and the longitudinal reheat, drawing and blowing machine are also feasible methods

The problem with

pp is that it has greater resistance to heat absorption and dissipation than pet, while the preform wall used for OPP bottles is generally thicker. Therefore, in addition to the low processing temperature (230 ℃) of PP in the bottle blank injection step, the cycle is also long. The OPP bottle is blown out at 130 ℃. Compared with pet, it consumes more energy and has a longer forming and cooling cycle. As a result, the processing speed that has reached 25% is slower than that of pet

pp stretch blow molding has a narrow processing temperature range of 5 ℃, while pet is 15 ℃, which increases the probability of shutdown and defective products. The stretching of PP is also different, which is something that bottle blank and bottle tool designers will have to be familiar with. In order to make the transparency of OPP close to that of pet, the stretching direction and stretching rate must be improved. Some parts of the preform, such as the bottom and neck, may be less stretched than the bottle body, making them easy to darken

pp's low hardness also means that o China Xinda Plastics Co., Ltd. (China XD plastics) PP bottles have smaller top load and hoop strength than pet. This and the unsatisfactory CO2 barrier performance have prevented OPP bottles from getting involved in carbonated beverages. In order to obtain the same hardness, OPP bottles need to have a larger wall thickness than similar PET bottles. Because the lower density of PP makes up for the increased wall thickness, OPP bottles are usually lighter than similar PET bottles

opp bottles have about 30 times the oxygen and CO2 permeability of pet, which makes them unable to be used as barrier containers unless they are coated or co injected with barrier resin

advances in materials are reducing the performance shortcomings of OPP bottles. One factor is millad 3988, a high-performance low residual transparency product produced by Milliken merican chemical company. Outside the United States, it is widely used in OPP bottles for vitamin, water, tea, fruit juice, detergent and medicine

our transparent agent has solved some important problems affecting OPP bottles, said Raj batlaw, market development manager of merican. These problems include obscurity (mainly at the neck and bottom), longer cycle time of bottle blank, and poor reliability of stretch blow molding process

advantages of OPP bottles

one of the few companies that actually manufacture OPP bottles in North America is CCC company in Canada. Norman Gottlieb, its CEO, said that the advantages in price and environment promoted CCC to enter the OPP bottle market a few years ago. He said that the enviroclear bottle, which combines OPP bottle body and PP bottle cap, is a fully recyclable and full PP system. Gottlieb also said that the standard PP bottle cap effectively covered the gray appearance of OPP bottleneck

gottlieb said: we have also seen opportunities for OPP bottles in terms of moisture resistance, squeeze ability and heat filling ability

although the oxygen and CO2 barrier properties of single-layer PET bottles are average, they are far better than single-layer OPP bottles. This limits single-layer OPP to applications with extremely short shelf life. Most bottles have a volume below 500 cc and do not need a lot of gas barrier

the second opportunity comes from the excellent heat resistance of OPP, which can withstand hot filling at 95 ℃. PET bottles can only be filled at ℃. They also require vacuum channels to prevent damage when filled above 80 ℃. Most pet hot filling applications require heating devices, which increases the cost by 20%

single layer OPP bottles do not need heating devices, which is feasible in many hot filled food markets, especially in the higher hot filling temperature range ((℃). This opens hope for barrier and non barrier packaging of fruit juice, jam, jelly, pickles, salads and ketchup

the third opportunity is in the market where both pet and OPP bottles need greater gas barrier. As long as the cost of barrier materials is almost the same for each container, barrier OPP bottles will be a better way to replace glass because of their cost advantages

three production methods

in view of the limitations of OPP production capacity, bekum and CCC have improved the pet equipment. They believe that the longitudinal linear reheating stretch blow molding system with 8 mold cavities is economical and efficient for medium-sized OPP production applications, and various resin storage, conditioning and pumping devices are installed

Gottlieb said: we inadvertently provided production equipment for OPP bottles. He pointed out that due to the lack of suitable machines and molds from commercial channels, CCC's initial efforts to produce OPP bottles six or seven years ago were stranded. Therefore, CCC has designed a suitable longitudinal reheating stretch blow molding line for opp. Its enviroclear device (which can also process PET) is built by Chinese partners and has a mold cavity. The machine can produce 900 bottles per hour per hole, but the next generation machine is expected to be upgraded to 1100. CCC provides stretch blow moulds with 32 preforms and cavities made in China, and the price is 40%-80% lower than that of local moulds in Canada

ccc says that the improved preform design is very important. The self-made preform is designed to have a 50% higher drawing rate than pet to improve transparency

bekum USA designed its reheating stretch blow molding device (such as double hole rbu-225) to be able to convert between pet and PP bottle production. A few years ago, bekum designed the first all electric reheating machine for pp. 3. After sales service: today's stretch blow molding machine SB-6. The production capacity of this 6-point machine is 7200 bottles per hour, which is just 15% slower than the pet machine with the same number of cavities

scott Steele of PTI advocated a different production method. He said that the best way to obtain the cost benefit of OPP bottles is to produce at a stable speed of 1000 bottles/cavity/hour on a rotary reheating stretch blow molding machine

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