Advances in materials, feed block/mold technology, and winding can help processors develop more complex cast-stretch products. #processingtips #bestpractices #dies

Nano-layer feed block and mold package from Cloeren. The nano-layer feed block is much larger than the traditional co-extruded block. For the mold, the shape of the runner must be rechecked, and the tolerance accuracy must be improved to meet the process requirements related to this thin layer

Here, the 17-micron LLDPE reference film is compared with a 15-micron seven-layer film containing Exceed mPE resin and Vistamaxx polymer. The thinner 15-micron film provides physical properties similar to the 17-micron film, as shown by the blue line in the center spider diagram. The graph at the bottom shows that although the weight of the film is much smaller, the retention of the thinner 15-micron film is almost equal to the retention of the 17-micron reference film. In addition, during the pallet packaging test, the 15 micron film broke under higher tension than the 17 micron reference film

Here, the 17-micron LLDPE market reference film is compared with a 15-micron nanolayer film containing Exceed mPE resin and Vistamaxx polymer. The thinner 15-micron film provides physical properties similar to the 17-micron film, as shown by the blue line in the center spider diagram. The graph at the bottom shows that although the weight of the film is much smaller, the retention of the thinner 15-micron film is almost equal to the retention of the 17-micron reference film. In addition, during the pallet packaging test, the 15 micron film broke under higher tension than the 17 micron reference film

The current distribution of purchased layer capacity between 2010 and 2015 indicates a surge in activity in European nanolayer technology. For the United States, the box marked underutilized capacity refers to installed capacity that has not been used due to patent litigation. Source: Cloeren Company

For high-speed, high-performance stretch film winding, the flexibility of the film width format must be maintained. On this W&H Filmatic PS winder, the trimming pick-up system provides seamless adjustability to remove trims in multiple roll widths

The dynamics of the stretch film market are constantly evolving. Globally, the main trends and driving factors for gypsum stretching are:

 • Thinning: The average thickness of the handbag has changed from 25 microns to 10 microns (µ), and the average thickness of the machine wrapping and strong pre-stretching has changed from 35 microns to 15 microns. The design of the cast film production line allows for the production of thinner films at higher winding speeds (up to 2300 ft/min or 700 m/min) than ever before. More flexible online winding has been developed to reduce labor costs and scrap rate.

 • Higher stretch percentage: The upper limit of the stretch range has been increased from 200% to 300%.

• End users use more machine packaging: The trend is to shift from manual packaging to machine packaging-this is the result of increased labor costs.

 • The packaging speed of the end user's machine is higher: the average packaging speed has been increased from 25 rpm to 60 rpm (the latter is only applicable to orbital/rotating arm packaging machines).

 • More layers: The trend towards multilayer films continues to grow and diversify. The film configuration ranges from three layers up to dozens of nano-layers. The nano-layer structure gives the film a "plywood" effect, enhances mechanical properties such as puncture resistance and tear resistance, and allows the use of thinner pure metallocene PE layers.

In Europe, nanolayer technology is developing rapidly. Advanced processors include Apeldoorn Flexible Packaging BV (AFP), a Dutch manufacturer of blown and cast films for packaging and has been using nanolayer technology since January 2009. AFP originally launched the nano-layer for the 27-layer film, but Eddy Hilbrink, who is in charge of the strategic research and development project, told Plastics Technology that it plans to further break the limit by installing a third nano-layer production line, which has more than 50 layers (see May Close-Up). ).

Among North American processors, no one seems to be even willing to discuss the number of layers. The patent litigation in 2012 may explain why. In February of the same year, a technology licensing company called Multilayer Stretch Film Holdings filed a lawsuit against nine leading stretch film processors in North America, claiming that they violated a patent involving seven or more stretch films. . Industry sources report that most of the nominated processors have settled out of court. However, last November, the Memphis Federal District Court ruled in favor of stretch film processor Berry Plastics, located in Evansville, Indiana. Multilayer Stretch Film Holdings has appealed the ruling. Berry will not comment on this matter.

Nonetheless, there are signs that since Peter Cloeren launched Chaparral Films in Orange, Texas in 1994, more processors in North America are surpassing the North American Free Trade Agreement region, which is generally considered to be the "most advanced" five. Layer structure. , Sigma Stretch Film, Lyndhurst, NJ, the largest stretch film manufacturer in North America, announced that it will install a nine-layer cast stretch production line from SML in Austria (located in the US office in Gloucester, Massachusetts), and is equipped with Cloeren molds/ feedblock package. The production line is expected to be delivered in the first half of next year and will be used to run a 20-inch wide roll nine. Another major processor, AmTopp Stretch Film Div. of the Inteplast Group, also recently announced a major extension (see the sidebar at the end of this article). Marketing consultant Mastio & Co., St. Joseph, Missouri, predicts that stretch film will grow at an annual rate of 4.5% by 2017, when it will consume more than 2.2 billion pounds of PE.

From a technical point of view, how can processors serving this market elevate it to the next level? Although the stretch line is huge and complicated, the three keys to develop a world-class stretch film are the material, the feed block/mold; and the winding. In this article, industry leaders in these areas (ExxonMobil, Cloeren, and Windmoeller & Hoelscher respectively) share their expertise.

Starting from the material, in trials with customers and leading machinery suppliers, ExxonMobil found that some of its resins provide ideal properties for stretch films:

 • Enable Metallocene PE (mPE) resin can provide high retention at low film thickness. • Exceed mPE resin provides high retention and puncture resistance at high stretch ratios. • Vistamaxx performance polymers are propylene-based elastomers that provide high tear resistance at high stretch ratios. These resins are also commonly used to provide reliable, cost-effective adhesion in these multilayer films.

Enable mPE is a branched metallocene resin. The metallocene resin series has higher shear thinning properties, allowing low melt index grades to be used for cast film extrusion to obtain better physical properties. The strain hardening curve shows that these resins have a significant second yield point, which provides a step change in tensile strength. The use of these resins in cast stretch films can produce high strength and high retention over a wide stretch range, thereby providing additional value in cast hand winding and machine winding applications.

Exceed mPE resin has become the industry standard for high stretch and high puncture resistance stretch films. The broad resin product portfolio (including Enable mPE and Exceed mPE resins and Vistamaxx polymers) is used to tailor solutions for specific equipment and application requirements. 

Vistamaxx high-performance polymers have better puncture resistance and tear resistance under high stretch and high tension. In addition, they provide a more effective adhesion solution.

Achieving adhesion in stretch films is an evolutionary process that began with the use of polyisobutylene (PIB). PIB is a viscous liquid and is difficult to measure into the product. Next comes the metallocene elastomer, which provides a cleaner and more precise alternative to achieve adhesion by mixing up to 30% of the substance into the adhesion layer. Today, the addition of about 10% or less Vistamaxx usually provides comparable adhesion performance, and its value is better than any of the previous options.

The stretch film industry uses a variety of multilayer configurations. A solution using Exceed mPE resin and Vistamaxx polymers has been developed. Compared with alternative solutions, it has the following advantages and can significantly save unit costs:

 • Improve toughness with thinner specifications. • Excellent pre-stretching and high-speed wrapping performance. • Calculated by weight, less film is required to wrap the pallet under the same load stability.

Figures 1 and 2 review two multilayer configurations that provide examples of value-added films. The seven-layer example is representative of the multi-layer approach and can be applied to other layer configurations, regardless of whether the number of layers is higher or lower. In both cases, the thinner film produces the same physical properties.

There are many options for customizing stretch film properties. ExxonMobil Chemical’s proven options for various scenarios include:

 • Enable mPE resin can be used to adjust the load force/working range. • Vistamaxx 3980FL provides improved stretch/puncture resistance in the nano-layer structure. • Exceed mPE resin has been used to improve many properties of stretch film. Exceed 3812CB provides adhesion/toughness improvement. Exceed 7518CB provides process continuity, adhesion, adhesion retention and tensile properties. Using it as the adhesive layer of Vistamaxx high-performance polymers can provide better adhesion and anti-blocking properties. It also provides softer, higher stretch films for the surface layer and/or core layer.

In addition, it improves the extrusion processing, edge flow stability and paper web stability, so that it can run stably at a higher speed and improve the continuity and consistency of the film.

Feeding blocks, molds, and nano-layers. With the commercial introduction of metallocene resins in the mid-1990s, the 15-year standard for three-layer stretch films was challenged. In 1994, Chaparral introduced the world's first commercial five-layer film to the market. Is this development "smoky" or "deceptive"? Some new things broke the status quo of the industry, and industry icons who had not yet understood the technology and its prospects did not respond in kind.

Fast forward to 2015, the film being processed contains more than 50 layers, and the song of "Smoke and Mirror" in 1995 once again sounded in some corners of the industry. According to reports, baseball legend Yogi Berra once said, “It’s like deja vu.” The industry has not jumped from a five-layer film to a 55-layer film in one fell swoop. Instead, it took twenty years to get there. At the turn of the 21st century, the industry witnessed the commercialization of seven-layer films and the serious use of polypropylene as a tear-resistant layer. Between 2000 and 2005, some companies even set foot in nine-layer films. The first 21-layer nano-layer film was introduced to the market by Pinnacle Films (now part of AmTopp). Next, AFP's industry experts and visionary Hilbrink launched a 27-layer film, and is now adding a third nano-layer production line with more than 50 layers.

Nowadays, it is rare to obtain new five-layer or even seven-layer capacity on large-scale commercial lines. To be fair, 9-layer and 11-layer capacities are the current standard, and nano-layer capacities are not uncommon. Figure 3 shows the current capacity distribution of the purchasing layer by geographic region from 2010 to 2015. So why are there more and more layers? One reason is that the polymers (including mPE, propylene-based elastomers, olefin block copolymers, LLDPE, ULDPE, and VLDPE) that can be used to build high-performance films today are significantly more stable than ten years ago. When you combine the available polymer options with the so-called "plywood effect", more layers are inevitable.

The plywood effect is the mutual reinforcement of layers (layers) to obtain unique properties. Plywood relies on the orientation of the texture structure in different or opposite directions to obtain its unique strength and flexibility. Although the co-extrusion film forming process does not allow each layer to have different orientations, in fact, discrete layers of different polymers do lead to different crystal structures in each layer. These different crystalline layer structures, when produced with the appropriate thickness of the appropriate polymer, provide mutual reinforcement. Therefore, more and thinner layers.

What is a nano layer? Nanometer is 1/1000th of micrometer. There are 25,400 nanometers in one mil. In cast films, the layers can be as thin as 100 nanometers. Then, when the film is stretched to more than 300%, the layer thickness will be less than 25 nanometers (0.0009 mils).

For example, many films produced today have a thickness of 10 microns or less, and even five-layer films may include sub-micron or nano-level layer thicknesses. However, as a practical problem, the industry seems to be reaching a solution, that is, the "nanolayer film" is composed of most layers less than 1 micron in thickness. Perhaps some 9-layer and 11-layer films, and of course all 20-50 layers, are technically in line with the development consensus definition of nano-layer films.

The laminar flow principle is applicable to all thermoplastic extrusion and co-extrusion. The number of layers has nothing to do with these principles. However, attention to design details will indeed increase significantly, if not multiplied. We at Cloeren assume that we know a lot of things, but it turns out that we don't know as much as we thought. There is a very quick way to increase the number of layers while reducing the layer thickness to make someone feel humble.

In order to meet customer expectations, new software must be developed, new tools implemented, and new manufacturing techniques applied. The feed block containing the nano-layer technology is much larger than the traditional (3 to 11 layer) feed block. Generally, as things become larger, the allowable manufacturing tolerances also become larger and more forgiving. This is not the case with nano-layer feed blocks: in fact, tolerances must be tightened to provide the required mass distribution accuracy, which is proportional to the number of layers involved.

At the same time, flexibility cannot obviously be sacrificed. This requires a modular design concept to be able to change layer position, polymer selection, etc. Modular and precision levers do not usually move in the same direction, but in this case, they must do so if they want to meet customer expectations. 

Then died. To evenly distribute the nano-thickness layer on a 3.5-5.5 m (150-220 inch) chip, the chip design needs to be re-examined. It is necessary to recheck the shape of the runner and improve the tolerance accuracy to meet the process requirements related to this thin layer. 

So what are the benefits of nano-layer stretch film? When looking at standard laboratory tests or controlled test standards, the results of nano-layer films are not obvious compared to traditional 7 to 11-layer films. However, when you look more deeply, or more deeply downstream of the process, other benefits will become apparent.

The outstanding performance of nano-layer films in practice lies in the packaging process itself. Typical orbital winding speeds are in the range of 20-25 rpm. When the nano-layer film is applied to the same wrapping process, under the same other conditions, we see that the achievable and reliable wrapping speed is at least twice that of the traditional film. For large bottlers and packers, this is equivalent to a large sum of money-each packaging machine has twice the number of pallets per hour.

What these field results tell us is that the nano-layer film produces a significantly higher allowable acceleration force. It can then be further assumed that if the allowable acceleration force is higher, then the allowable deceleration force is also higher. The allowable deceleration force is particularly important in Europe. In Europe, pallets are loaded sideways, and the nesting of pallets is inherently impossible, just like the end-load trucks in the United States.

High winding quality is essential for reliable and safe use of stretch film in tertiary packaging. Most of the challenges in the winding process are closely related to the extrusion process, so a close combination of extrusion and winding is essential. Sub-micron film profile tolerances are inevitable, and they are stacked layer by layer in the film roll, so that the film is deformed and damaged in the wound roll. In some applications, the stretch winder must be designed for frequent reel changes in order to maintain a high extrusion line speed. 

The "TNT" principle of winding is to control the basic parameters of the pressure accumulation in the roll: the tension of the film, the clamping force between the contact roll and the film roll, and the torque on the center reel of the roll. The TNT setting determines the overall tightness of the film layer in the roll. At the same time, the outer layer of the film in the roll acts as the compression band of the inner layer, especially on the paper core where the pressure is the highest. Depending on the film resin formulation, the film may "aging" due to heat shrinkage and post-crystallization after production. For example, a stretched film with a PP functional layer shows significant changes in its mechanical properties, and subsequently tends to generate higher core pressures during storage.

Three different types of stretch film are usually produced: manual stretch film, machine stretch film and super-strength stretch film. These films have application-optimized properties in terms of extreme stretch, retention, puncture, tear propagation resistance and adhesion. All these parameters will affect the slitting and winding processability.

For example, the winding tension of the ultra-thin and super-strength stretch film should be as low as possible to prevent the core from crushing. In addition, the application will affect the roll size. In order to be compatible with packaging machines, rolls used for machine packaging have a standardized roll diameter of about 10 inches and a fixed film width of 20, 30, or even 40 inches. In contrast, hand-wrapped rolls may have any width in the range between 10 and 20 inches. The final hand-applied roll diameter is less than 10 inches. Sometimes there are only a few thousand feet of film on the core.

Hand-wrapped rolls can be produced online by extrusion or offline production by cutting larger "jumbo" rolls, typically up to 16 inches in diameter. The high production speed of up to 2300 ft/min combined with the small roll diameter results in a roll change cycle time from 30 seconds to several minutes. According to the width of the roller and the die, the extruded web is divided into up to 12 webs at the slitting station of the winder. 

Usually, "bleeding" trims are cut between the roll paper so that the core of the roll at the center of the roll extends to the edge of the roll. These trims are usually sticky and highly expandable; they must be reliably cut at high speeds and fed back into the extrusion process for better material and energy efficiency. All in all, on a winder, one stretch film product may be very different from another. All in all, the winder needs to provide high flexibility, easy handling of complexity, high reliability, and-last but not least-good coil quality.

The high-speed production of stretched film requires a dedicated winder that combines all three TNT principles. In the case of W&H's Filmatic PS winder, two winding units are stacked on top of each other in a laterally offset arrangement, half of each winding unit. The same web path through the two winding units ensures a consistent roll quality on the entire web. All rolls in the winder are optimized to increase traction at low web tensions to produce thinner films. 

In addition, the tension zones for slitting and winding are mechanically isolated from each other to enlarge the processing window. The unique and sturdy bearing assembly for the winding shaft ensures minimal deflection during the winding process, ensuring perfect curling and consistent winding stiffness at high speeds. In addition, the winder provides an innovative function that can optimize and maintain the winding hardness by fine-tuning the air in the winding gap.

Traditionally, the elimination of air in the roll is the most important. Now, with the advent of higher-performance, thinner stretch films that run at higher line speeds, there is a need to control the air distribution throughout the reel. 

Controlled softness rolls have the following advantages: • Low unwinding force reduces film breakage in the stretch packaging machine head. • Low unwinding noise is a prerequisite for the warehouse's fully automatic packaging line. • A higher level of adhesion is essential for load stability and higher load retention. • Eliminate film wrinkles so that there is little film breakage when stretched on the wrapping paper. • The ability to run thinner machine film cores provides huge potential savings for film converters.

The automation system is mandatory at high web speeds to achieve operator safety and process stability. Each winding turntable has three winding shafts, so the paper core can be loaded on one shaft, and the paper roll can be pulled out from the other shaft in parallel with the winding process.

At the same time, the flexibility of the film width format must be maintained. Therefore, each winding turret has core bins for two different core lengths. The core in any bin can be combined with the manually fed core size in the programmable core mode. The operator can easily access all the core bins of the two turrets in one location.

The new trimming suction system in the slitting station provides flexibility in the width format and simple operation. The position of the flow-optimized suction tube can be seamlessly adjusted according to the roll width to obtain the best slitting performance and stability. Finally, a dedicated high-speed axis can be used to handle any core patterns that may be required.

Winding a good stretch film may be the most demanding part of the production process. The features listed above simplify the winding process through additional adjustability and enhanced flexibility.

AmTopp's tiered approach supports growth strategy

Author: Jim Callari, Editorial Director

AmTopp Stretch Film Division of Inteplast Group. With 13 stretch lines in four locations in the United States, the most recent installed capacity is approximately 320 million pounds per year. The picture is Scott Stevens, sr. Head of product and business development for Inteplast.

The layer explains why the AmTopp stretch film division of the Inteplast Group. It is one of the largest stretch film processors in North America. It has been nearly 25 years since the start of its first production line in Lolita, Texas. "Layer" does not just refer to a thin film layer. When you base the concept of continuous improvement on the promise of diversified and flexible product lines, R&D, new technology investment, shortened delivery time and customer service, the company's stretch film success formula becomes clear.

In the past five years alone, the company has more than doubled its production capacity by adding production lines and acquiring the Pinnacle Films business in Charlotte, North Carolina. Its recent investment of US$15 million to purchase two new multi-layer production lines will bring about 320 million pounds of production capacity to 13 strains from four plants. 

In addition to Lolita and Charlotte, AmTopp also produces stretch films in Phoenix and Houston, Arizona. One of the two new routes will be in Charlotte; the other will be in Phoenix. Currently, it is believed that only Sigma Stretch Film Group and AEP Industries in Montville, New Jersey have more capacity. The Charlotte line is expected to be put into operation by the end of 2015; the Phoenix line should be put into operation sometime in the first quarter of next year.

AmTopp officials said that the two new production lines do not mark the end of its expansion plan. In fact, the company saw an opportunity to sell stretch film outside the borders of the North American Free Trade Agreement. "We are firmly committed to this industry and will continue to expand," said President Homer Hsieh. "We believe that the economy is improving and the cost of polyethylene in North America will be globally competitive in the long term, which will support our goal of becoming an exporter of stretch film made in the United States."

Although all of AmTopp's capacity is multi-layered, the company does not want to specify how many layers there are. "We invest in research and development," Scott Stevens, sr. points out. Head of product and business development for Inteplast. "But it's not all about layers. We are open to new technologies and keep up with the times, which is consistent with our position in the industry. Ultimately, market demand, our customers' needs, and investment in new technologies and new equipment The expected return on investment will drive decision-making.

"For stretch films, our goal is to meet customer needs and meet their specific application requirements at a competitive price," Stevens added. "It is possible to over-design the movie to give it more performance attributes than to meet the specific purpose. This does not benefit the end users because they end up paying for more features than they need."

Stevens said that product diversity helps differentiate AmTopp from competitors. "We produce a variety of cast film products designed for specific applications," he elaborated. "We produce machine films, manual films, and specialty films for our customers. If customers need highly engineered films, we have them. If they need something more basic, we have them too."

Hsieh added: "We provide stretch film solutions for every application of our customers. This is our unique advantage in the market. We launched a pre-stretch film in 2014, which has proven to be the most successful in our product catalog. One of the launches. The entire group-manufacturing, sales and marketing-are committed to process, product and continuous improvement, with a focus on providing our customers with consistently high-quality products."

In North America, stretched films are sold through distributors, while European film processors have more direct contact with end users. Compared to most European countries, this is a simple function of the size of the United States. Although European filmmakers see this as a competitive advantage, Stevens pointed out that AmTopp spends a lot of time and energy training its distributors on how to use their films and how to use them. Stevens stated that the distribution network will not separate AmTopp from its customers. "We are directly involved, especially those famous people." 

Driven by the group president, Dr. John Young, continuous improvement is deeply rooted in the Inteplast Group. "This is Inteplast's ongoing practice and an important part of our company culture," Stevens said. "It is deeply ingrained in everything we do. We never stop asking ourselves how we can be better and more effective, and we strive to put the best ideas into practice."

Almost all extrusion processes pass the melt through a wire mesh screen on its way into the die to provide filtration and improved mixing.

Particle quality and consistency are critical to any compounding operation. However, various problems may be encountered during the underwater pelletizing process. This is the way to fix them.

Placing one or two vents between the feed port and the die is a good way to remove moisture, trapped air, and other volatiles as the molten plastic passes through the extruder.

© 2021 Gardner Business Media, Inc. Privacy Policy [Login]