Improving Diaper Performance While Saving Money.
Exactly one year ago, I shared a short article entitled “Short Fibers and The Paradox of Pad Integrity, Myth or Reality?”, this published article was viewed by thousands of colleagues in the diaper industry and later translated by a pulp manufacturer to other languages. In this article I discussed the benefits of using short fibers, like Eucalyptus fluff, as a way to increase pad capillarity for better wicking, to reduce diaper thickness, save packaging costs, and improve perceived softness. I also debunked some of the myths about short fibers and pad integrity that have accompanied us for almost 60 years. Many people contacted me with questions on how to apply these concepts and specially about a simple guideline they could use during manufacturing. This time, I will do my best to share some tips and suggestions on how to cash the benefits, explaining why this is an interesting opportunity to save money, while improving the performance of the diaper at the same time.
We all know that diaper softness is no longer just an extra, today is one of the most important requests that we get from our customers everywhere. New nonwoven technologies had to be implemented and they keep evolving because of this consumer need. Diaper softness is typically improved by replacing the backsheet with softer components; by using higher loft or higher GSM materials; and by embossing sophisticated 3D textures to give the optical illusion of softness. High loft materials unfortunately, have proven to be a liability risk, as they may end up with some of their nonwoven fibers de-bonding and in the mouth of babies. What is not so well known, is the fact that you can also improve diaper softness a great deal just by making a softer absorbent core. You have probably experienced a minor improvement in softness when you replaced the tissue wrapping material with a nonwoven core wrap while keeping everything else the same; imagine how much softer it can feel if you were able to change the whole core and replace it with a softer core, not just the wrapping. I know you may be tempted to change diaper core softness by just reducing pad density and keeping the same ingredients in your core construction, believe me, this is not going to work because you will end up with higher packaging costs and even potential pad integrity issues, and to make things worse, this is going against a market trend that I want to address next.
A better way to achieve softness, is by blending eucalyptus fluff into your core. How much eucalyptus you need to blend depends on the final product you want to make. Products that are made for low capacities, for example feminine liners or diaper booster pads, could be made without blending; products that are not subject to strong user activity, like under-pads and pet pads, can also use the eucalyptus fluff without the need to blend it with pine fluff. Other products, those that need higher integrity cores, like those cores used for baby diapers or pants (especially when used by toddlers), and like those used for adult underwear, should be blended with pine fluff to achieve the desired softness, but without sacrificing any pad integrity. Adult briefs, like those made with double drum formers, have the very best situation, they can take advantage of the density gradient created by using pine and eucalyptus at different layers in the same core. You can basically increase the number of fibers and the pad density by blending some eucalyptus, resulting in a more compact and softer core. In my opinion, you can achieve similar levels of perceived softness without having to spend as much money in backsheet improvements.
The need of thinner products is a global trend for baby diapers, consumers in mature markets prefer the thinner cores as they want their babies to use clothing with a better more ergonomic fit. They want their babies to look nice. For those consumers using adult products, it is a much more critical issue. They need briefs and disposable underwear to be more discreet, not just for their own dignity, but also to allow them to carry them while traveling or while on the move. They have to be much thinner, but without sacrificing a single bit of their performance. Thinner diapers are more ergonomic, and they are obviously more discreet than the thicker alternatives. From another point of view, there is also the added benefit to be able to save money on the packaging and during distribution. So thinner products do save money, but how thin should they be?
Recently, after reading hundreds of consumer reviews and after being invited into a few home user tests in the USA, I have seen that fluff-less cores have a tendency to be early leakers, especially after the second insult with urine. Avoiding the “early leakers” in fluff-less cores is a complex design problem, one that requires extensive engineering resources. Not many diaper factories have these resources. In my personal opinion, unless these fluff-less cores are balanced with the correct amount of cross-linked fibers (like curly) or use a much higher weight ADL, it is not uncommon for diapers made with some fluff to outperform the fluff-less variety, especially when they are insulted under certain specific body positions. For this reason, I do not see many diaper brands rushing to visit their OEMs to buy machines to make their diapers fluff-less, like the Pampers. Again, making thinner diapers is the natural advantage of blending short fibers with your regular fluff, but without the need to go all the way to being fluff-less.
In order to maximize the capacity of an absorbent core, you need to increase its pad utilization. You can improve diaper capacity by improving the wicking of the core. Increasing the ADL may help in this regard, but this can be expensive, in addition if you extend the ADL too much to cover a full pad width, or a full pad length, you will end up favoring leakages at the very edge of the core. This is the reason why an ADL needs to stay as a patch instead of full pad coverage. Increasing the capillarity of the core without increasing its cost is a much better alternative. This is where a eucalyptus blend can out shine pine alone. As you decrease the spacing between the fibers by increasing core density you also increase the capillarity, it is not the fibers themselves that hold most of the liquids as the spacings between these fibers, this is a well-known phenomenon in fluid dynamics. This is also why a core made with a blend of eucalyptus exhibits a higher pad utilization, something that it is not always easy to validate at the laboratory, but that you can confirm when you measure the maximum capacity before leakage (MCBL) with mannequins or better yet with home user tests done with real people.
Another requirement from consumers today is the need to sell a more environmental story, this is why products are starting to differentiate by using more sustainable materials. It is a known fact that eucalyptus is a better alternative to pine with regards to carbon capturing. CO2 is captured at a peak rate during the first years of the growth of the tree, so younger trees growing during their first years are more efficient than the older more mature trees ( *https://psmag.com/environment/young-trees-suck-up-more-carbon-than-old-ones ).
By using more eucalyptus trees instead of pine, the cutting cycle can be reduced to one third of the required time, and more trees will be replanted and in their peak CO2 capturing mode, for better net carbon sequestration. I also believe that post-consumer recycling, where diaper components are recycled instead of being thrown to the landfill or incinerated, is going to happen within a few more years, probably within the next 5 years or so. Once this is a reality, we will have a net negative carbon cycle and disposable diapers will be by far the best consumer alternative, for sure better than biodegradation, incineration, or cloth diaper use.
In summary, you can start saving money by blending eucalyptus fluff into your mill. Ok, but how do you go about doing it? First you need to take into account that you will need to increase the debulking in your diaper line. By how much should you increase the pad compression in the diaper line? Most likely around a 15 to 20% reduction when you use a 50% blend of eucalyptus and pine -the exact amount will depend on the humidity of the purchased pulp and the relative humidity in the plant, but probably as much as 25 or 30% if you do not need to blend it with pine. Keep in mind that due to pad resiliency after debulking, the actual physical reduction in the gap will not match the actual reduction in thickness of the core, so a bit of trial and error will be required. Even at its most conservative estimate, a reduction in product volume of 15% can easily translate into net product cost savings of at least 2% when you add packaging and distribution savings, and twice as much if you can avoid the need to blend it with pine fluff.
Keep also in mind that you will need to test for pad integrity to make sure that you have similar performance to the one you had before you added the eucalyptus blend. If needed, Diaper Testing International located in Houston can perform 3rd party testing for performance and pad integrity for a relatively low price. There is of course the possibility to add pad integrity hot melt adhesives as an option to increase pad integrity, keep it in your “tool box” as an option during your test trials. For 50% blends the need to use pad integrity hot melt adhesive will be minimal or unnecessary for most cases, but as you increase the blend of eucalyptus and reduce pine you may have to compensate with some specialty hot melt. This is a very similar situation to the one we already experienced when nonwoven replaced tissue wrapping, or when pad ratios were increased from 40% 10 years ago to the new SAP ratios that are higher than 60% today. The risk of the pad breaking apart increases with the increase in the SAP ratio. Pads made with 100% eucalyptus will probably also need a bit thicker ADL to compensate for the slower intakes of fluid that is expected of more dense pads. I expect this additional cost to be less than the savings obtained by the reduced packaging and distribution costs, with the benefit of the softness, the better wicking, and the environmental advantages. With very rare exceptions, I believe most products will find benefit if they are open to consider the blending of short and long fibers as I have explained.
Finally, do not believe what people tell you (not even me!), not until you are able to validate on your own, in your own diaper line, and with your own running conditions. That is probably the best advice I can give you today.