How was rinse-free washing, which has revolutionized the laundry process, accomplished?

In February 2023, Lion launched Acron Smart Care, a laundry detergent (for delicates) with fabric-softening ingredients. This product, which challenges conventional wisdom by enabling the washing of clothes without washing, was developed and refined over approximately four years from conception to launch. Playing a central role in the laboratory was researcher Takei, in charge of fabric care product development. We spoke to him in detail about the process of developing the product’s features.

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Product Introduction

Make clean in short time and environmentally friendly laundry a reality by rinse-free washing Acron Smart Care, a laundry detergent (for delicates) with fabric-softening ingredients

Thanks to the realization of our rinse-free washing technology, this laundry detergent (for delicates) eliminates the rinse stage, which accounts for 70% of the laundry process and can damage clothes. This product not only makes quick and eco-friendly laundry a reality, it also satisfies the desire to preserve and wear one’s favorite clothes for longer periods of time while providing a completely new method of washing and caring for one’s favorite clothes.

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Benefits born from a “rinse-free” detergent

It was back in 2019 when Takei first hit upon the idea of developing a rinse-free laundry detergent. At that time, Takei was part of a new team that was tasked to create the seeds of technology from which new products would blossom. Rather than working on a specific product, this team’s job was to come up with one idea after another. He remarked that there were times when he’d draft 1,000 ideas and then discuss them with his fellow team members. Among those ideas, just what was it that led the team to decide to develop a rinse-free laundry detergent?

“Reducing the number of rinse stages is beneficial for the environment as doing so also reduces the amount of water and electricity used during washing. Several companies were already producing laundry detergents with a single rinse stage at the time, so the concept of reducing the number of rinse stages was not all that unusual. Still, we thought that some consumers might be wary of the idea of a rinse-free washing stage. So, we reasoned that this product could compete in the market if it could offer laundry detergency with the same cleaning strength as conventional products—even without rinsing—and could bring a benefit that convinces customers to consider making the switch from their conventional washing habits to try this new product.” 

Together with his team, Takei considered the value rinse-free washing could provide. 

 Initially, one of the candidates was to cut down on the amount of time spent doing laundry. Most washing machines are designed to have two rinse stages in one wash cycle. This means that after the first wash, the wastewater is emptied, fresh water is added, rinsed, drained and spun and the cycle is repeated. If the rinse stages were entirely removed, though, laundry times could theoretically be reduced by half at the very least.

Comparison between conventional and rinse-free laundry process

The rinse-free laundry detergent’s development was also spurred by the realization that eliminating the rinse process can considerably reduce the amount of water consumed; if commercialized, the detergent would be environmentally friendly and contribute to realizing a resource-circulating society.

Comparison of reductions in water, electricity, and CO2 emissions by number of rinses (2 times/0 times)

Moreover, it was anticipated that eliminating the rinse stage would do less damage to clothes because it would cut down on the total amount of time they are submerged in water, which only needs to be drained once. The team verified on a trial basis that there would be fewer wrinkles and less sagging after rinse-free washing. 

 Pondering the possibility of applying this value to laundry detergents (for delicates)—where minimizing damage to clothing is especially important—Takei started working on the rinse-free technology that would eventually be known as Acron Smart Care. 

New technology that makes rinse-free washing a reality

Each member of Takei’s research team is responsible for a certain theme and leads its development. As rinse-free technology was Takei’s theme, he conducted a number of experiments on the subject, starting with decreasing the surfactant content in detergent. 

Although surfactants are designed to remove soil from clothing, they might still be present on clothing after washing. For this reason, in a conventional laundry process, any remaining surfactant is removed during the rinse stage. In other words, to accomplish rinse-free washing, the maximum amount of surfactant must be removed during the wash stage. 

“We considered reducing the amount of surfactant used in laundry process to allow it to be thoroughly rinsed away during the washing stage. Reduced surfactant, however, leads to reduced detergency, which must be compensated for through other functional ingredients. Moreover, as there’s no longer a rinse stage, it was important to prevent the soil from redepositing on the clothes after it’s removed. Our research thus began with a search for the functional ingredients that would satisfy two requirements: high detergency and anti-soil redeposition ability.” 

Experiments were extensively conducted with a variety of functional ingredient compositions being explored

Takei reduced the surfactant concentration to about half that of conventional detergents and searched for functional ingredients that work effectively even under such conditions. Lion’s research laboratories have accumulated knowledge regarding various ingredients because adding ingredients other than surfactants to detergents has been done in products developed up to this point. However, it is impossible to refer directly to previous findings. Because the majority of the previous findings were obtained under conditions of relatively high surfactant concentration, and it was unknown how the functional ingredients would work under conditions of low surfactant concentration. Takei was forced to attempt each one on their own after realizing the knowledge he already possessed could not be applied. 

“Our hypothesis was that if the ingredients were structured in such a way that they could efficiently approach the soil on the clothes and surround it once it was removed, we could achieve both high detergency and anti-soil redeposition ability. In the end, however, we had no way of knowing how the ingredients would work until we tested them. We put all of our effort into continuing our experiments. First, we tried it on a small piece of cloth, and when that seemed to work, we moved on to clothing, trying over 100 different ingredients. When we finally managed to find the one, I was ecstatic.” 

 It was decided to incorporate the functional ingredients discovered by Researcher Takei into a new product; a laundry detergents (for delicates) in the Acron line. The ingredient was also given the name of the new product into which it would be incorporated—the Acron Smart Care ingredient. 

 As shown in the figure below, the Acron Smart Care ingredient surrounds soil and not only removes it from the clothes, but also prevents it from redepositing. 

Illustration of the Acron Smart Care ingredient function

The Acron Smart Care ingredient—which was discovered during an analysis of its detergency against sebum stains—performed admirably when it came to meeting the demands of laundry detergents (for delicates), as it was found to be capable of effectively removing wine and cosmetic stains.

Results of washing experiments with Acron Smart Care on various types of soil

Additionally, it was demonstrated that rinse-free washing using Acron Smart Care had the same detergency ability for sebum stains as that demonstrated by conventional Acron, which uses a one-rinse washing method, and that the amount of residual surfactant left on the clothes was identical. 

*Click here to see a video of a detergency experiment with the Acron Smart Care ingredient. (Japanese only) 

 The most noticeable difference was in the wrinkling and sagging of clothes. Compared to a two-rinse wash, it was obvious that a rinse-free washing resulted in fewer wrinkles and less sagging. 

Comparison of wrinkling and sagging by number of rinses

(→Details of the technology: Research case study URL) 

A future in which rinse-free washing becomes the standard

This time, Takei was in charge of not only nurturing technology in its early stages before it became commercially viable but its eventual commercialization. 

 “There was a chance that as I was on a new team cultivating the seeds of the new technology, others would handle the product’s commercialization once it reached that stage. However, I personally requested to take charge of that as well, which was a rewarding yet pressure-filled experience. To effectively communicate the value of the product—which was to offer an unprecedented washing experience—the research institute was involved in product communication and packaging development through consumer surveys and other methods. We needed to think from the perspective of consumers, not researchers.” 

 Takei was instrumental in the research and commercialization of Acron Smart Care, the rinse-free laundry detergent launched in February 2023. Takei expressed his satisfaction as a researcher at seeing his creation on store shelves. 

 Several technologies developed to achieve rinse-free washing have been patented. In April 2023, a poster presentation on this technology was made at an international conference hosted by academic associations related to fats, oils and surfactants,* where it was lauded as an excellent technology that contributes to reducing environmental burden.  

* Presentations given at the 2023 AOCS Annual Meeting & Expo

Takei reporting his results at the conference

Currently, Takei is conducting various studies, such as improving the Acron Smart Care ingredient, in order to make this rinse-free washing technology more widely used. 

“Rinse-free washing is something that many may not be familiar with right now, but I’m sure those who use it will be pleased with the results. Hopefully, in five or ten years time, it will become the standard worldwide. Rinse-free washing provides an environmentally friendly way of taking care of your clothes. We will continue working to improve Acron Smart Care and create new products to make its use even more widespread.” 

 Products, contents, and affiliations are as of the time of the interview. (Interviewed Aug 2023) 

Researcher Takei 
Since joining the Company, he has been a member of a new team within the department tasked with fabric care product development, where he has been responsible for discovering the future seeds of technology and their commercialization.