Toray develops waste-cutting adhesive film for fabrics

Adhesive products attached to fabric or clothing, such as stick-on body warmers and medical pads, have their adhesive surfaces protected by a liner known as release paper. This paper prevents them from sticking to skin or other substances, but it needs to be peeled off before their use. Materials manufacturer Toray Industries has developed an adhesive film that, even without release paper, does not stick to skin or other substances and adheres securely only to fabric. Because it does not damage fabric, wide-ranging applications in daily goods, healthcare, and apparel are expected. The elimination of release paper waste also leads to waste reduction.

Moriaki Niizaki, a development engineer at Toray's Environment & Mobility Development Center in Otsu City, was told by a customer about five years ago: "It is wasteful to just throw away the release paper." Upon looking into it, he found that a large amount was disposed of as waste, which led him to think, "Is it possible to develop an adhesive film that could be handled without using release paper?"

Although he discussed what materials to select with his colleagues, good ideas did not easily come to mind. One day, while Niizaki was making fried chicken at home, he noticed that using too little flour caused stickiness, while using too much resulted in a dry, smooth texture.

Thinking "Perhaps we should adjust the surface area covered by the flour," he tried sprinkling flour-like powder onto the adhesive film at the factory. However, the film production line became contaminated with powder, and there was also a risk that the physical properties of the powder might change at the delivery destination. He conducted repeated experiments to achieve a condition where "the surface behaves as if sprinkled with powder, without actually applying loose particles that could be buried or shed." As a result, he arrived at the idea that forming convex structures on the adhesive surface, like being sprinkled with powder, might work.

When convex structures of 10 to 20 micrometers were added to the adhesive surface, an adhesive film was created that did not stick to flat surfaces such as skin, metal, or plastic, but adhered selectively to wavy fibers. When underarm sweat pads and name stickers were prototyped using this, they attached properly to clothing while not sticking to other flat objects.

The prototyped adhesive film is 6 micrometers thick, and it can be made thinner or thicker than this. Confirming that peeling it off after applying does not damage fibers, Toray states that "it can also be used for delicate materials." The film is made of polyester, and an advantage is that the fabric does not become stiff when applied, preserving the natural drape and flexibility of the fabric. Toray foresees that it can be expanded into fields such as healthcare and apparel, in addition to daily necessities such as cooling sheets, pad-type diapers, and nursing pads.

Release paper peeled off during the use of stick-on body warmers and other products is discarded. According to Toray's estimates, using this new release-paper-free adhesive film for stick-on body warmers is expected to reduce waste by 247 tons annually. In addition, the weight of the body warmer excluding the heating element can be reduced by 60%, and the thickness can also be reduced by 38%, achieving "both product compactness and environmental impact reduction simultaneously."

Toray is working on creating environmentally friendly fibers and materials and created this adhesive film as part of those efforts. The company stated: "We want to continue creating products that can contribute to sustainability in the future." The achievements were announced by the company on April 21.