From the first disposable baby diaper by CHUX, now Johnson & Johnson, in 1949 to Kimberly Clark’s introduction of adult diapers in 1984, the disposable hygiene industry has come a long way. These products have changed the world. They have transformed how people live our daily lives in a variety of ways. And now, as manufacturers explore and experiment with new disposable hygiene core designs, the future for these products is even more exciting.
In the beginning
Early disposable diaper designs were very simple—yet they were still considered luxurious. The core was a stack of 15 to 25 sheets of tissue paper. They could hold an estimated 100 ml of fluid, which meant they needed to be changed after every use. Plus, they did not have the features we see today, like elasticised waistbands, leg cuffs, re-fastenable ear tabs, and wetness indicators.
But parents came to love disposable diapers, and their popularity grew. Competition among manufacturers grew as well. Just one year after the original tissue-core diaper was released, the first fluff core (made of cellulose wadding) by Paulistrom was introduced. It was cut, sized and put in reusable panties to help with fluid absorption and distribution, as well as improved performance.
Superabsorbent polymer becomes the game changer
Disposable hygiene made another big leap in the 1980s with superabsorbent baby diapers. This began when Unicharm introduced superabsorbent polymer (SAP) in Japan.
Compared to an all-fluff core, SAP could hold greater volumes of fluid, even under pressure. But SAP alone tends to absorb and wick fluid slowly, so fluff had to stay for absorption speed and wicking. To increase absorption, manufacturers began to add greater amounts of SAP to the fluff in the core matrix.
Core designs today
Currently, there are multiple sets of fluff to SAP ratios used by manufacturers in traditional style cores. The most common two—and where the use of adhesives are most critical—are:
50% fluff to 50% SAP
At this ratio, the fluff fibres are entangled to create a pad that keeps the SAP in place and supports core integrity. To improve core integrity even more, a core wrap can be used. The wrap surrounds the fluff/SAP and is sealed with a core adhesive.
70% SAP to 30% fluff
Manufacturers find themselves facing more challenges at this ratio. At 70% SAP, a core wrap and a core adhesive are needed to prevent the loss of SAP powder. Bostik has seen that a core at this ratio that does not use an adhesive will immediately fail the Conditioned Core Cracking Test because there is too much loose SAP powder. The core adhesive helps keep the SAP in place to improve core performance.
The future of fluff-free cores
As product producers look towards reducing the thickness of their cores, fluff-free cores are an option. With these designs—and incorporating new SAP that has better wicking and absorption speed—SAP stabilisation is more important. No fluff means there are no cellulose fibres to hold the SAP powder in place, and adhesives become even more critical. The pre-compound or compound core, which typically consist of multiple layers of nonwoven or tissue with SAP, is one option. Another is the channel core which features channels free of absorbent material. (Note that some producers do include fluff in their channel core designs.)
If exploring new core designs is in your sights, we strongly recommend involving Bostik’s core adhesive experts in the early stages of development. With our expertise, we can help you quickly identify the nonwoven adhesive solutions that best meet your design needs.
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