Whitening mechanism of fluorescent whitening agent

It is necessary to understand the white increase of fluorescent white agent. First of all, we must understand the relationship between light and color. Ancient Greek philosopher Aristotle believes that light is color, and the existence of light can have color, because there is no sight without it. The only source of the color of all objects, when the light stimulates the human retinal, it forms color sensation. Without light, there is no color. A kind of electromagnetic wave from the sun, other celestial bodies, flames, and artificial light sources. Its range is wide. When the wavelength is too long (infrared area) or too short (ultraviolet light zone), the human eye cannot be distinguished.

Only the narrow light zone between the wavelength range between 380 and 760 nanometers is the visible light area of the human eye. The longest wavelengths of the balanced distribution of the visible light region have been found to be red, and then orange, yellow, green, blue, and purple in order. You can also see it when you pass through the prism.

The type of light source, the absorption of objects and reflective light can determine the color of the objects we see. When the light is irradiated to an opaque object, the surface of the object will absorb most of the visible light, and reflect part of the visible light, and the color of the reflection of light is the nature of the object. For example, a piece of lemon yellow and yellow fabrics absorb almost all colors except yellow except yellow. White objects almost reflect all the colors in the light, while black objects absorb almost all colors. The color of any object can only be seen in the white light. In fact, the light itself is not completely colorless.

A fluorescent whitening agent is a color conditioning agent, which has a bright and white effect, and is widely used in many fields such as papermaking, textiles, and washing agents. There are about 15 basic structures of fluorescent whitening agents and nearly 400 structures. There are two types of fluorescent whitening agents that are allowed to be added to the detergent of clothing: di -styrene -based pedibin (such as CBS, etc.) and bisotinorine amine (such as 33#, etc.).

The principle of fluorescent whitening agent is to absorb ultraviolet light that is not visible in the light, and emit visible blue light. After superimposed with the yellow light from the fabric, it complements the white light to increase the white light emitted by the fabric. Bright white, this is the bright white effect. The fluorescent whitening agent can absorb the invisible ultraviolet light. The wavelength of the original incident was more visible in the range of 400-600 nm, which made the product look white, brighter and more bright.

It can be seen that the fluorescent whitening agent is different from the addition of the adding blue whitening. The former lies in the latter to reduce the light. When the light is strong, it can greatly exceed 10%. In the past, people believed that the objects that could make 100%reflection of incident light should be the whitening. After the fluorescent whitening agent came out, people got this white. From the perspective of people's visual consciousness, the blue tone is white than the white tone. Therefore, within a certain limit, the increase of blue saturation can be added.

Since the fluorescent whitening agent has the function of bleaching, how does it work? The whitening characteristics of the fluorescent whitening agent are determined by the special structure of its molecule. Its hair color group has a co -pyramid system that can occur in π → π*jump. The most common systems are benzene, rings, triazine, ethylene groups, five -yuan heter ring, and other thick ring systems. The electronic system with a small degree of common levels generally only absorbs the light of the short wavelength. As the common cricket system increases, the wavelength of absorption of light increases, the more vulnerable to the electrons will be stimulated. Requirements for fluorescent whitening agents.

In order to improve the comprehensive utilization performance of fluorescent white agents, color aid groups also need to be introduced, including pushing electronic groups (such as alkyo, alkyl, substituted amino groups, etc.) and pull electronic groups (such as sulfonate, cyano, carboxyl group, etc. ), These groups will affect the nature and strength of fluorescence. Some groups have less influence on the color system, but can change the application performance of fluorescent white agents and affinity for fiber and plastic. The structure of the fluorescent whitening agent cannot contain nitro, nitroin or heavy nitrogen groups. Although they can increase the sun exposure, these groups will weaken or even completely eliminate fluorescence.

So how does the fluorescent whitening agent work in the white substance? The fluorescent whitening agent is presented in different substances. In the field of detergent or textile printing and dyeing, the whitening agent has water -soluble it. Its state in plastic matrix is a process of dissolution and gathering. It is refined and dispersed or even dissolved in it with various additives after melting with various additives through plastic matrix. Therefore, there are two possibilities in plastic fluorescent whitening agents: the ideal state of the ideal state of a single molecule in a fiber baaine or detergent in the plastic is uniformly dissolved in the polymer matrix, or it exists in refined particles or other forms.

When using fluorescent whitening agents, the biggest problem encounters is the yellowing phenomenon after the fluorescent whitening agent is added. This is caused by the poor solubility of the substrate to the fluorescent whitening agent. At this time, because the amount of fluorescent whitening agent is difficult to control and the impact of migration in the substrate, the substrate of the fluorescent whitening agent whitening is often easy to yellow.