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Paper Straws in Beverage

How to Develop Liquid-Resistant Paper Straws

Posted 03/09/2021 by Erin L'Hotta, Marketing Manager, Paper Converting

As more and more consumers are adopting an “anti-plastic” movement mindset, paper straws are becoming an increasingly important alternative. 

Finding the Right Liquid-Resistant Paper Straw Adhesive is Critical 

To ensure a paper straw does not unravel during use, there needs to be a strong liquid-resistant adhesive holding the paper together. The paper manufacturer, paper grade, machine type, and paper color are all variables to consider when choosing the right adhesive. 

H.B. Fuller’s adhesive solutions comply with direct liquid contact regulations. While submerged in a liquid, the adhesive provides strength to ensure the straw maintains its form. It is additionally important that the adhesive bond enables straw composting after a paper straw is used. 

Paper Straw Test Methods 

Paper straw manufacturing is affected by a range of challenges, including how the adhesive is applied to the paper, the type of equipment used, the use or not of a heater, and the machine speed. Quality control testing ensures the final paper straw meets quality requirements and safety standards. When conducting a quality control test, one must use the same paper at the same temperature, humidity, machine, operator, the same amount of glue at the same temperature and compare those results after the same drying time. 

Fiber Tear Testing

A paper straw fiber tear test verifies that the amount of adhesive will enable production of a strong straw. The paper manufacturer can conduct this test themselves or work with H.B. Fuller to do so as part of their quality control process. Assessing the fiber tear performance at the end of the line is the first test. Achieving fiber tear at the end of the line verifies that the machine is operating as expected and that the amount of adhesive used will form a strong bond. A strong bond is essential to water resistance. 

Liquid-Resistance Testing

This test evaluates how long it takes for flagging, or unraveling, to occur when the straws are submerged in liquid. This is the most important quality control test. It is conducted a minimum of 24 hours after the adhesive is applied. To correctly assess paper straw liquid resistance, the straw must be placed in a certain direction in the liquid. It is advised that you test the straw in the liquid on the weak end, which is where the outer layer is uncovered, versus the strong end of the straw. Once the straw is in the water, it can be stirred occasionally and assessed for how long it takes for the straw to demonstrate signs of flagging. 

H.B. Fuller Swift®tak Paper Straw Adhesives

H.B. Fuller’s Swift®tak water-based adhesives produce three hours of liquid resistance. These products run fast and create a durable straw. H.B. Fuller conducts robust product testing in our laboratories and have validated that the average straw using Swift®tak adhesives lasts three hours in water and more than five hours in carbonated soft drinks before the straw starts to unravel or become excessively soggy. Although liquid resistance performance is paper- and liquid-dependent, on average Swift®tak adhesives perform better than the paper straw industry’s requirements for two to three hours of liquid resistance. 

Our new generation adhesive allows for a new level of manufacturing efficiency with paper straws. Swift®tak 5730 gives a competitive advantage for core winding and slot nozzle application for straight or bendy cold drink straw production, like those often used in juice boxes. Since the adhesive generally comprises less than 5% of the total dried weight of a paper straw, paper straws can be recycled and industrially composted*.  

This technology allows paper straws to be compliant with German Federal Institute for Risk Assessment (BfR) Food-Contact Recommendation BfRXXXVI (Paper and Board for Food Contact Materials) for food contact to help ensure maximum consumer safety. Although the BfR recommendations are not legal norms, they are widely industry respected throughout the European Union. Swift®tak 5730 also is FDA 176.170 direct food contact compliant for maximum consumer safety.

* Results are coat weight, paper, and liquid dependent and subject to variability.

At H.B. Fuller, our team of experts are ready to provide the adhesive solutions the paper straw industry needs to continue to grow in popularity and usage. Connect with us today to learn more about manufacturing paper straws and our Swift®tak products.

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