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Adhesive solutions for a thinner core

Source:Ringier Nonwovens     Date:2014-10-10
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THIN IS IN in the diaper market. Wherever you are in the world, hygiene manufacturers are looking at aspects of diaper construction to create competitive products with less bulk. This has brought the core construction under scrutiny as it is the thickest part of the diaper.

Evan Yuan of HB Fuller Asia Pacific

Evan Yuan, Asia Pacific senior R&D chemist and technical service manager for Hygiene at H.B. Fuller, collaborates with manufacturers to design lighter, better disposable diapers

Evan Yuan, who has a postgraduate degree from the Chinese Academy of Sciences, has been talking to us about the vital role adhesives play in achieving core integrity and how consideration of the adhesive solution in the early stages of the design can make a significant difference to the size, performance and competitiveness of the final product. At the Asia Disposable Hygiene and Personal Care Products Summit last June in Shanghai, Mr. Yuan’s  thought-provoking presentation attracted considerable interest.

Mr. Yuan is instrumental in translating the market requirements into added value product developments for core integrity at H.B. Fuller, where he is Asia Pacific senior R&D chemist and technical service manager for Hygiene. His team carries out extensive evaluations manufacturers working with adhesive solution providers to help achieve increasingly thinner cores without  without compromising performance of hygienic disposable articles, and gives invaluable service to customers to understand the adhesive performance within the final product.

The drive for thinner cores

Opening the conversation with some background on why the trend towards thinner cores has proved particularly popular in the Western world, Mr. Yuan said, “Reducing the size of the diaper core delivers benefits for the end user and the supply chain, as well as making good environmental sense.  

While the thinner core trend in the Western world has been particularly noticeable in the last couple of years, the traditional high fluff content thicker diaper still dominates in emerging markets. Mr. Yuan said he expects the trend in thinner cores is likely to grow, particularly as consumers see the benefits of improved comfort and fit. “Babies benefit from a more comfortable and better fitting product, while adult consumers benefit from enhanced discretion,” he explained.

“Manufacturers can make material savings and the reduced bulk impacts the supply chain as there is less product to transport and store; plus shelf space is optimized,” Mr. Yuan said. “This approach also brings environmental benefits with less energy consumption and less end-product waste.”

A partnership approach to R&D

The core is the thickest part of the diaper, so is the obvious focus of research. “R&D investment has recently accelerated with manufacturers and suppliers collaborating together on development projects. This partnership approach is likely to continue given the desire to create even thinner hygiene products,” Mr. Yuan confirmed.

This approach is very much a global phenomenon, with all the major brands particularly in Europe having already made significant strides forward. “Initially diapers developed with less bulk failed to deliver on performance and in the European market, where competition is intense, consumers will not tolerate compromised performance,” he explained. “To successful reduce the size of the core, the contribution of adhesive solutions to its integrity needs to be understood and designed into the core structure at the outset.”

Understanding core integrity

A typical core is made up of fluff and SAP, which absorbs, distributes and holds the fluid to prevent leakage until the diaper is changed. In addition, there is an acquisition layer which sits on the top of the core to wick the moisture away from the wearer and distribute it to the core quickly and efficiently.

“In modern baby diapers, the core is wrapped in nonwoven or sometimes tissue. This is where the adhesive is applied to fix the core. In many diapers the core is enclosed by overlaps at the sides which are laminated together or manufacturers use the ‘C-fold’ core wrap, meaning the nonwoven is wrapped around the entire core,” explained Mr. Yuan.

“Most adult incontinence diapers have a more simple structure with the fluff core directly between the top-sheet and back-sheet substrate, with the adhesive solution fixing the structure together.  Whatever the design the core fixation adhesive is a fundamental part of the puzzle which makes up the diaper core,” he added.

thinner, lighter infant diapers

Reducing the size of the diaper core means baby is more comfortable in a better fitting product

Creating optimal solutions

A technical understanding of all factors of core integrity is required to make sure the core structure performs, stays intact and does not separate when wet, or shift and clump. The adhesive solution and measurement methods are a fundamental part of delivering this absorbent core strength, combined with other factors including fiber length and fiber entanglement, pad density, SAP distribution; core shape and structure, and liquid distribution. “Working in close collaboration with hygiene manufacturers, we can help look at the impact of varying the amounts of core fixation adhesive on core integrity by keeping other core parameters consistent,” Mr. Yuan said.

In line with this approach, as there are multiple types of adhesive technology to choose from, his team also identifies the best core fixation adhesive for the customer. While the traditional standard construction adhesive can be used, he said manufacturers can now benefit from speciality core adhesives which penetrate the porous core. “Speciality core adhesives from H.B. Fuller are based on an enhanced delayed crystallization effect, which means the adhesive can flow and fix a greater number of fibres before it reaches its final bond strength. This makes stronger mechanical anchoring and a high wet strength more achievable,” Mr. Yuan explained.

“Early consideration and testing of the options available can make a significant difference. At H.B. Fuller we have a wealth of technical knowledge and experience, combined with our comprehensive Full-CareTM range of premium hot melt adhesives. We are well-placed to work in partnership with manufacturers, helping them to address their industry challenges, progress new concepts and deliver the latest hygiene solutions.”

He confirmed that another approach being used for thinner cores is to create a fluff-less diaper, which requires a complete redesign of the core in which the SAP can be fixed in different ways within other substrates.

“There are already some of these concepts out in the market-place in which adhesive technology can play an important role,” he noted.

Creating thinner cores for diaper products is set to continue with innovation being accelerated through the effective collaboration of manufacturers and suppliers to develop optimal solutions. This trend is increasingly seen in  emerging markets, where it is clear that adhesives will play a vital role in the construction of the core.

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