Cross-laminated timber pioneer KLH is the only manufacturer who started an industrial CLT production already in the last century (1999). Since then, KLH not only improved the product itself but also the production line. Repeatedly, the Styrian company expanded, modernised and optimised its production site in Teufenbach-Katsch.
At the beginning of one of the latest projects was the idea to use two adhesives with different open times instead of one. “The thought behind this was to further increase our machines’ flexibility and throughput capacity”, tells us managing director Johannes Habenbacher. When producing thin panels with few layers, open time as wells as pressing time can be reduced significantly without sacrificing adhesion quality.
Quality comes first
KLH’s managing director Johannes Habenbacher is satisfied with the outcome of the project and wants to make the most of Flex A’s potential in the future. © Günther Jauk
As a rule, adhesives of the Loctite HB S Purbond product line are admitted for only one precisely defined open time – depending on the catalyst added. With Flex A, the goal was not to develop a new type of adhesive, but to use the optimal product with precisely defined characteristics for every batch that enters the press. This was done by online-mixing of a “fast” (with a minimum open time of 4 minutes) and a “slow” (open time of up to 70 minutes) adhesive. Henkel’s Flex A system had been in the concept stage for a while and now, the company found the first suitable industrial partner, namely KLH, for the successful market launch of this system.
“Apart from the technical implementation, quality assurance was a major challenge”, says Dr. Andreas Neumüller of Holzforschung Austria. For this purpose, Henkel developed a new testing procedure for the immediate determination of adhesive reactivity. “Understandably, cost efficiency plays a central role for our customers. When it comes to load-bearing wood structures, however, the top priority is always a safe construction in line with building law”, explains Dr. Christian Lehringer, Head of Henkel Engineered Wood Europe.
Exact dosage
Market leader Oest is responsible for the adhesive application. Contrary to previous CLT-projects, where the focus was on the exact dosage to be applied on the wood, the challenge of this project was the precise mix ratio. “Only when the mixing and dosage process is absolutely reliable, the desired characteristics can be guaranteed”, says Neumüller with regard to the importance of the application system.
More precisely, Oest implemented a Kontitop Z dosage aggregate with servo dosage technology for Henkel’s 1K-PUR-adhesives. The two Henkel Loctite HB-S Purbond adhesives react differently and can be applied either separately or with different mix ratios. Furthermore, Oest built a portal for two adhesive application tables for the first time.
The second dimension
For practical purposes, the project partners opted for a handful of pre-defined mix ratios. “In theory, any mix ratio is possible, of course. However, for everyday work there is a need for clearly defined times and therefore also for pre-defined mix-ratios”, explains Neumüller. Based on previous data and experience, the machine operator can estimate the necessary open time of a batch and set the optimal mix ratio accordingly.
For Lehringer, Flex A opens up a second dimension when it comes to flexibility: “Already now, our clients could adapt their open time exactly to the minute by using the HB-S-line. With Flex A, manufacturers are also more time-independent during the single pressing processes. This increases throughput and as a result also cost efficiency.”
Enormous potential
KLH implemented the new system during the winter revision of 2017/18. After the final inspection by Holzforschung Austria, production started in January. For the moment, the Styrian company uses few different mix ratios. “Flex A has an enormous potential. In order to make the most of the possibilities, other production steps need to be adapted first”, says Habenbacher regarding the company’s future plans.
Successful project
The new kindergarten in Teufenbach-Katsch was one of the first projects which used elements glued together by using the Flex A system © KLH
For Lehringer, Flex A is a showcase project in many respects. “Flex A allows us to further confirm our status as technological leader in the area of certified 1K-PUR-adhesives.” As to the project schedule, the involved partners agree: “Everybody has done their part in a reliable and professional way. The motivated and technically sophisticated collaboration of all project partners was the key to the success of this project.”