Is the era of the hottest OPP bottle coming

2022-08-11
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Is the era of OPP bottle coming

you 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, OPP is cheaper and more heat-resistant than pet, but at the same time, it has low hardness, poor transparency and barrier properties, and is more 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. Hard OPP containers made by one-step injection and blow molding and two-step reheat stretch and blow molding machines are once again claimed to be a good opportunity to change the cost of packaging water, fruit juice, hot filled food, dry powder and personal care products

surendra agarawal, head of food research and development at Kraft, said, "we are looking forward to a step-by-step change in the manufacturing cost of OPP bottles." Compared with glass, OPP bottles are lighter, harder to break and easier to grasp by hand. The density of bottle grade PET is up to 1.35 g/cc. The system also provides complete engineering support for customers. The current price is 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

about 57billion PET bottles were used in North America in 2002. The high-yield rotary reheat stretch blow molding machine can blow 60000 bottles per hour. In contrast, OPP bottles are currently limited to the narrow application space of infant nutrition and medicine bottles, mainly in Asia and South America. They are mainly made on a one-step injection, drawing and blowing device, which cannot make a difference in the huge 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 the defects of OPP

until now, the disadvantages in processing speed and physical properties compared with pet have hindered the development of OPP bottles. However, OPP 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 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 corplast and other companies, OPP bottles are very competitive. However, suppliers of competitive equipment point out that one-step injection, drawing and blowing machines and tandem reheat, stretching and blowing machines are also feasible methods

The problem with OPP is that compared with pet, it has greater resistance to heat absorption and dissipation to achieve sustainable development, while the preform wall used in 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. Opp bottles are blown out at 130 ℃, which has higher energy consumption and longer molding and cooling cycle than pet. As a result, the processing speed, which has reached 25%, is slower than that of pet

opp stretch blow molding has a narrow processing temperature range of 5 ℃, while pet is 15 ℃, which increases the probability of downtime and defective products. The stretching of OPP 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 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

the lower hardness of OPP also means that OPP bottles have smaller top load and hoop strength than pet. This and the unsatisfactory CO2 barrier performance have made OPP bottles unable to get 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

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

progress in materials is shrinking OPP, so it is easier to integrate into existing electronic research than graphene; 2 is the performance disadvantage of the two-dimensional boron bottle. One factor is millad 3988, a high-performance low residual transparent agent product produced by Milliken merican chemical company. Outside the United States, it is widely used in OPP bottles for vitamins, water, tea, fruit juice, detergents and drugs

"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 bottle blank cycle time, and poor reliability of the stretch blow molding process

advantages of OPP bottles

one of the few companies that really manufactures OPP bottles in North America is CCC company in Canada. Norman Gottlieb, its CEO, said that the advantages of 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 completely recyclable full PP system. Gottlieb also said that the standard PP bottle cap effectively covered the gray appearance of OPP bottleneck

gottlieb said, "we also see 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 general, 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 need vacuum channels to prevent damage when filling 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 the barrier and non barrier packaging of fruit juice, jam, jelly, pickles, salads and ketchup

the third opportunity is in the market where 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 they have cost advantages

three production methods

in view of the previous limitations of OPP production capacity, bekum and CCC have improved pet equipment. They believe that the in-line linear reheating stretch blow molding system with eight die cavities is economical and efficient for medium-sized OPP production applications

Gottlieb said, "we inadvertently provide production equipment for OPP bottles." he pointed out that due to the lack of suitable machines and molds from commercial channels, CCC's efforts to produce OPP bottles with flexible and diverse control methods, which was first produced six or seven years ago, were stranded. Therefore, CCC has designed a suitable longitudinal reheating stretch blow molding production 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 said that the improved preform design is very important. Its self-made bottle blank is designed to have a 50% higher tensile 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. Bekum designed the first fully electric reheating stretch blow molding machine SB-6 for PP a few years ago. The production capacity of this 6-point machine is 7200 bottles per hour, which is just 15% slower than pet machines 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

source: Jiagong electromechanical

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