Application and safety of optical brighteners/fluorescent whitening agent

2020/11/16

1. How fluorescent whitening agents work

 

It is well known that white matter tends to absorb slightly the blue light in visible light, which to some extent causes the lack of blue color, making it slightly yellow and old. Fluorescent brighteners are somehow dyed to a certain whiteness of textile, paper, plastic, detergent and other substrates, when exposed to sunlight or other light sources containing ultraviolet light, the fluorescent whitening agent will absorb the invisible ultraviolet light (wavelength 300 ~ 400nm) and emit the bright blue-violet fluorescence (wavelength 420 ~ 480nm) , and complement with the yellow light on the substrate to get the white light, thus has whitening effect on the article. Because fluorescent brighteners convert invisible ultraviolet light into visible light, increasing the intensity of the reflected light, the objects look whiter and brighter.


The addition of a certain variety and appropriate amount of fluorescent whitening agent in the detergent can not only improve the appearance of the detergent, but also increase the whiteness or brightness of the washed fabric, improve the washing effect, and make the white fabric white and bright, brighten up a light-colored fabric. Therefore, the fluorescent whitening agent has become one of the important auxiliaries in the fabric detergent formulation. The textile industry is the earliest application field of fluorescent brightener, natural fiber, synthetic fiber fabrics after refining after bleaching still with yellowish. Fluorescent brightener can absorb ultraviolet light and emit blue-violet fluorescence characteristics of the yellow, so that the fabric whitening. At the same time, it can be used to increase the brightness of the fabric, so that the light-colored fabric bright.

 

2. Whether the more the fluorescent whitening agent is added, the better

 

The answer is no. Fluorescent brighteners should be used in trace amounts. Otherwise, the effect is counterproductive, because the intensity of yellow light on the fabric is limited, the necessary fluorescent whitening agent emitted complementary color light-blue-violet fluorescence is limited. With the increase of the concentration of the fluorescent whitening agent on the fabric, the intensity of its blue-violet fluorescence also increases, it emits blue-violet fluorescence and yellow light on the fabric cancel each other, the fabric whitening effect is the best. And once the blue-violet fluorescence intensity is greater than the yellow light intensity on the fabric, the appearance color of the fluorescent whitening agent itself will also appear, it will cause the reduction of whitening effect so fluorescence. Whitening agents are not used as much as the better.It works best in the right amount.

 

3. Safety of fluorescent whitening agents

 

From the beginning of the last century, fluorescent whitening agent has developed from being mainly used in textile to being mainly used in detergent and soap, paper making, all kinds of textiles and plastics, coatings, anti-counterfeiting and other industries. Up to now, it has been used for more than 70 years at home and abroad. At present, there has never been a case of illness or personal injury caused by fluorescent whitening agent. Moreover, some of the nearly 400 fluorescent whitening agents with structural registration numbers have long since been eliminated after years. Dozens of commonly used varieties still being produced and used in the world have been proved to be low toxic or basically non-toxic by toxicological data, it’s safe to use. It has been proved that the fluorescent whitening agent is safe not only for consumers, but also for the workers who produce the fluorescent whitening agent. But why are concerns about fluorescent whitening agents being reiterated? This is because: First, people may only see the early hypothesis and unproven descriptions that fluorescent whitening agents can slow blood clotting or cause cancer, and did not take note of the later toxicologists after scientific rigorous research reached the opposite conclusion; second, some businesses in order to promote the sale of their products, with the aid of the mass media wantonly exaggerated the toxicity of fluorescent whitening agents and the possible harm to the human body, this is also one of the main reasons for people’s misunderstanding of fluorescent whitening agents.