Improvements in blown film techniques

Efficiency and resource-saving blown film technologies have created a major leap and these were very much apparent at the recently concluded K 2022 where improvement in blown film systems were highlighted. One company, Kuhne Anlagenbau GmbH showcased a new technology for the production of simultaneously biaxially oriented thermoforming films; while  Addex Inc. Introduced its integrated blown film cooling and stabilisation systems for extrusion lines. 

Kuhne: Triple Bubble® technology

Kuhne Anlagenbau GmbH exhibited for the first time at K 2022 as a manufacturer of large-scale lines for producing simultaneously biaxially oriented thermoforming films using Triple Bubble® technology. At a thickness of 80 to 120 µm, these films are only about half the thickness of conventional cast films used in this application, and there is no need to compromise on service characteristics either. The maximum achievable thermoforming ratio is 1:10. This means a reduction in material consumption and thus in the associated greenhouse gas emissions of some 50%.

Thanks to optimised cooling rates, these large-scale lines can achieve throughputs of up to 2,000 kg/h or annual outputs of as high as over 15,000 tonnes per year, which means that they can match or even surpass the productivity and profitability of cast film lines. Inventory can also be reduced in downstream processing, while the distinctly lower energy consumption of thermoforming enables a further reduction in CO2 footprint and very good machine processability is also ensured. For manufacturers and distributors, the reduced thickness of the films means lower extended producer responsibility (EPR) levies and assists compliance with the Circular Economy for Flexible Packaging (CEFLEX) sustainability guidelines drawn up by the flexible packaging value chain.

Kuhne's  Triple Bubble® technology  for producing simultaneously biaxially oriented thermoforming films. 

Typical applications for such multilayer films include shelf-life extending vacuum packaging for the transport and storage of large pieces of ham, meat or cheese. Generally based on PA, EVOH and PE, these films combine high transparency with good thermoforming characteristics and elevated puncture resistance. Kuhne Anlagenbau, which developed the Triple Bubble® process in-house back in 1996, has perfected the system and can now offer processors access to the attractive combination of low film thicknesses with the high throughputs which can only be achieved with large-scale machinery. This means the economic advantages traditionally enjoyed by cast films over blown films in this area are a thing of the past.

The Triple Bubble® technology for manufacturing biaxially oriented blown films is named after the serial arrangement of three bubbles. In the first, the film is rapidly cooled using cold water quench technology. Kuhne has further optimised this process for the large-scale plants, so enabling the efficiency-enhancing increased cooling rates which very effectively prevent crystallisation processes as a prerequisite for uniform stretching in the following, second stage. The high level of orientation at the molecular level achieved in this second stage significantly improves the films’ mechanical and barrier properties. Thermal relaxation in the third bubble serves to set the desired thermoforming behaviour.

Kuhne Triple Bubble® lines currently enable the production of films with up to 17 layers at widths of up to 3,000 mm double flat (6,000 mm film width) and an output of as high as over 2,000 kg/h. The systems are suitable for processing any conventional polymers such as PE, PP, PET, PA, EVOH, COC, EVA, EMA, ionomers etc. Thermoforming formulations which, depending on the weight of the packaged goods, contain well below 10% PA and EVOH, also permit a dramatic reduction in thickness and ensure easy, high-performance processing. Monomaterial solutions based on PET, PA, polyolefins and further polymers are also possible.

Addex: Blown film cooling and stabilisation system 

Addex Inc. unveiled its integrated blown film Cooling and Stabilization System (CSS) for extrusion lines. The digital, automatic bubble cage (Dcage) features Addex’s “Operator-Assist” (Å) technology which controls the entire cooling process on one screen.   The company has partnered with Pearl Technologies, Savannah, N.Y. create a robust, “smart” bubble cage featuring Addex’s proprietary 100% pure digital automatic controls. The Addex + Pearl Digital Bubble Cage provides smooth, consistent bubble diameter control and features Pearl’s unique patented cage arm technology. Each cage arm is fabricated from a lightweight custom aluminum extrusion with a smooth, fully radiused active surface that always faces the bubble. Surface-modified with Pearl’s SM24 “Extreme-Slip” ultra-low coefficient of friction (COF) hard-coat material, the resulting design offers long wear life and superior quality film without blemishes, tracks, or chatter marks. Addex has engineered control over stepper motors to perform precise repeatable axis adjustment for vertical positioning of the cage, as well as the horizontal adjustment for bubble diameter integrated with their all-digital IBC Control System (DIBC).

Digital, automatic bubble cage features Addex's “Operator-Assist” technology

Addex's bubble cage system represents a breakthrough in the blown film industry. The company's depth of process knowledge coupled with a strong desire to make operator-friendly equipment was the impetus behind the “smart” Bubble Cage + DIBC and the resulting Å - Operator Assist technology. Additionally, all the system components are service friendly, allowing remote maintenance-friendly diagnoses/troubleshooting, thus avoiding delayed and costly in-person technical service calls.  Addex's Digital IBC Control (DIBC) uses patented, split, fully-digital ultrasonic sensors that eliminate errors caused by interference common to other systems and enable the air flow intake and exhaust to react to the slightest change in bubble size. This occurs while retaining high precision and accuracy over the resulting bubble size. Additionally, a digital stepper motor valve control retains this high degree of precision to ensure tighter control over the entire process, as well as repeatability. 

Also new to the Addex lineup and displayed as part of the Digital Bubble Control System is Short Stack Intensive Cooling, the latest iteration of Addex’s patented Intensive Cooling technology. Short Stack is an enclosed two-level, stacked Intensive Cooling system that guarantees 15% to 20% output gains with low-melt strength materials that typically are impossible to run on other raised-up cooling systems. Short Stack also provides up to 50% output gains with easier to run, high-melt strength materials. The Short Stack stabilisation and bubble cooling immediately upon exit of the die is the key to impressive output gains while maintaining film quality through enhanced bubble stability. Short Stack Intensive Cooling also features digital control over that portion of the cooling process, including Å-Operator Assist technology and remote maintenance capability. 

- This article also appears in the International Plastics News for Asia - December issue. To read the electronic version of the magazine, click here.