Adidas has agreed to subscribe for 3 million euros ($3.65 million) worth of shares in the company's planned initial public offering, bringing the total investment it has secured to 58 million euros, Spinnova said in a statement.
"We are an ideal match with the ambitious and pioneering Adidas sustainability strategy," Spinnova CEO and co-founder Janne Poranen said.
Spinnova is building its first commercial factory in Finland with strategic partner and wood raw material supplier Suzano, and is also building a pilot facility for fibre production out of leather waste.
It said Adidas wanted to secure access to "significant volumes" of its patented fibre in future.
A 500 million euro sustainability bond Adidas issued last September was five times oversubscribed, with proceeds earmarked for investing in renewable energy production and projects to promote recycled materials.
Adidas has pledged to shift to using only recycled polyester from 2024 and is also involved in research cooperation with another Finnish start-up, Infinite Fiber, to develop a process that can transform used clothes into a cotton-like material.
($1 = 0.8218 euros)
(This story corrects description of company in headline)
(Reporting by Emma Thomasson; editing by Jason Neely)