Fluorescent whitening agents, processes for their preparation and use

Abstract

This invention relates to a fluorescent whitening agent, its preparation method, and its application. The fluorescent whitening agent has the structural formula shown in formula (1), in which n and m are each independently selected from natural numbers greater than or equal to 2, R1 and R2 are each independently selected from -OH, -COOM, -SH, or -SO3M, and R3, R4, R5, and R6 are each independently selected from -H, -COOM, or -SO3M, wherein M is selected from -H, -Na, or -K.

Description

Technical Field

[0001] This invention relates to the field of fluorescent whitening agents, and in particular to a fluorescent whitening agent, its preparation method, and its application. Background Technology

[0002] Optical brighteners, as important fine chemical products, have a wide range of applications and promising market prospects in industry. Currently, large amounts of optical brighteners are mainly added to paper, cotton fabrics, and coatings to improve whiteness. However, existing optical brighteners have low dispersibility; when the concentration is high, molecules may overlap, leading to quenching of the brightener. Furthermore, existing optical brighteners have poor lightfastness, thus affecting the whitening effect. Therefore, there is an urgent need for an optical brightener with high dispersibility and lightfastness to improve its whitening effect and practicality. Summary of the Invention

[0003] Therefore, it is necessary to address the above-mentioned problems by providing a fluorescent whitening agent, its preparation method, and its application. The fluorescent whitening agent provided by this invention has good dispersibility and lightfastness, thereby improving the whitening effect and practicality of the fluorescent whitening agent, and has a wide range of applications and good market prospects.

[0004] A fluorescent whitening agent, with the structural formula shown in formula (1),

[0005]

[0006] In equation (1), n ​​and m are each independently selected from natural numbers greater than or equal to 2, R1 and R2 are each independently selected from -OH, -COOM, -SH or -SO3M, R3, R4, R5 and R6 are each independently selected from -H, -COOM or -SO3M, where M is selected from -H, -Na or -K.

[0007] In one embodiment, n and m are each independently selected from natural numbers from 5 to 20.

[0008] A method for preparing the fluorescent whitening agent as described above includes the following steps:

[0009] A mixture of cyanuric chloride and ice water was subjected to a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid, followed by the addition of an aromatic amine to carry out a second condensation reaction, to obtain a stilbene triazine molecular skeleton.

[0010] Alternatively, a mixture of cyanuric chloride and ice water is subjected to a first condensation reaction with an aromatic amine, followed by the addition of 4,4′-diaminostilbene-2,2′-disulfonic acid to carry out a second condensation reaction, yielding a stilbene triazine molecular skeleton.

[0011] The stilbene triazine molecular backbone is subjected to a third condensation reaction with an amino polyethylene glycol derivative to obtain the fluorescent whitening agent, wherein the structural formula of the amino polyethylene glycol derivative is shown in formula (2). In equation (2), n is a natural number greater than or equal to 2, R1 is selected from -OH, -COOM, -SH or -SO3M, and M is selected from -H, -Na or -K.

[0012] In one embodiment, the molar ratio of the cyanuric chloride to the 4,4′-diaminostilbene-2,2′-disulfonic acid and the aromatic amine is 1:(0.45~0.50):(0.95~1.05).

[0013] In one embodiment, in the step of performing a first condensation reaction between a cyanuric chloride ice-water mixture and 4,4′-diaminostilbene-2,2′-disulfonic acid, followed by the addition of an aromatic amine for a second condensation reaction, the aromatic amine is selected from aniline;

[0014] Alternatively, in the step of a first condensation reaction between a cyanuric chloride-ice-water mixture and an aromatic amine, followed by a second condensation reaction with the addition of 4,4′-diaminostilbene-2,2′-disulfonic acid, the aromatic amine is selected from p-aminobenzenesulfonic acid or monosodium aniline-2,5-disulfonic acid.

[0015] In one embodiment, the structural formula of the stilbene triazine molecular skeleton is shown in formula (3), formula (4), formula (5) or formula (6).

[0016]

[0017] In one embodiment, the molar ratio of the stilbene triazine molecular backbone to the amino polyethylene glycol derivative is 1:2.1 to 1:2.5.

[0018] In one embodiment, during the first condensation reaction step, the pH of the system is adjusted to ≤5 and the temperature to ≤5°C;

[0019] And / or, in the second condensation reaction step, the pH of the system is adjusted to ≤9 and the temperature to ≤60℃;

[0020] And / or, in the third condensation reaction step, the pH of the system is adjusted to 9-10, the temperature is adjusted to 90℃-103℃, and the system is refluxed for 3-5 hours.

[0021] In one embodiment, in the first condensation reaction and the second condensation reaction steps, a soda ash solution is used to adjust the pH of the system;

[0022] And / or, in the third condensation reaction step, the pH of the system is adjusted using a liquid alkali solution.

[0023] The application of a fluorescent whitening agent as described above in paper fiber whitening, textile fiber whitening and coating whitening.

[0024] The aforementioned fluorescent whitening agents have a special molecular structure. On the one hand, fluorescent whitening agents have high stability, and the ether bonds in the fluorescent whitening agent molecules can form strong hydrogen bonds with the hydroxyl groups in the fibers, effectively improving the lightfastness and practicality of the fluorescent whitening agents. On the other hand, the steric hindrance between fluorescent whitening agent molecules is relatively large, and the molecules are not easy to aggregate, which is conducive to improving dispersibility, reducing the quenching of fluorescent whitening agent molecules, and thus improving the whitening effect and lightfastness of the fluorescent whitening agents.

[0025] Therefore, the fluorescent whitening agent provided by the present invention has good dispersibility and lightfastness, thereby improving the whitening effect and practicality of the fluorescent whitening agent, and has a wide range of applications and good market prospects. Detailed Implementation

[0026] To facilitate understanding of the present invention, it will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to make the disclosure of the present invention more thorough and complete.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments or examples only and is not intended to limit the invention. The optional scope of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items.

[0028] The fluorescent whitening agent provided by this invention has the structural formula shown in formula (1).

[0029]

[0030] In equation (1), n ​​and m are each independently selected from natural numbers greater than or equal to 2, R1 and R2 are each independently selected from -OH, -COOM, -SH or -SO3M, R3, R4, R5 and R6 are each independently selected from -H, -COOM or -SO3M, where M is selected from -H, -Na or -K.

[0031] The aforementioned fluorescent whitening agents possess a unique molecular structure. On one hand, they exhibit high stability, and the ether bonds within the molecules can align directionally after drying, exposing the lone pair electrons of the oxygen atoms. This allows them to form upper and lower hydrogen bonds with the hydroxyl groups in cellulose, effectively improving the lightfastness and practicality of the fluorescent whitening agents. On the other hand, the steric hindrance between fluorescent whitening agent molecules is relatively large, making them less prone to aggregation. This improves dispersibility, reduces quenching of fluorescent whitening agent molecules, and thus enhances the whitening effect and lightfastness of the fluorescent whitening agents.

[0032] Therefore, the fluorescent whitening agent provided by the present invention has good dispersibility and lightfastness, thereby improving the whitening effect and practicality of the fluorescent whitening agent, and has a wide range of applications and good market prospects.

[0033] Preferably, n and m are each independently selected from natural numbers from 2 to 40, which is beneficial to further improve the dispersibility and lightfastness of the fluorescent whitening agent, so as to further improve the whitening effect and practicality of the fluorescent whitening agent. It can be understood that n and m can be the same or different.

[0034] More preferably, n and m are each independently selected from natural numbers ranging from 5 to 20.

[0035] The present invention also provides a method for preparing the fluorescent whitening agent as described above, comprising the following steps:

[0036] S1. A mixture of cyanuric chloride and ice water was subjected to a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid, followed by the addition of an aromatic amine to carry out a second condensation reaction, to obtain a stilbene triazine molecular skeleton.

[0037] Alternatively, a mixture of cyanuric chloride and ice water is subjected to a first condensation reaction with an aromatic amine, followed by the addition of 4,4′-diaminostilbene-2,2′-disulfonic acid to carry out a second condensation reaction, yielding a stilbene triazine molecular skeleton.

[0038] S2. The stilbene triazine molecular skeleton is subjected to a third condensation reaction with an amino polyethylene glycol derivative to obtain the fluorescent whitening agent, wherein the structural formula of the amino polyethylene glycol derivative is shown in formula (2). In equation (2), n is a natural number greater than or equal to 2, R1 is selected from -OH, -COOM, -SH or -SO3M, and M is selected from -H, -Na or -K.

[0039] It should be noted that the amino polyethylene glycol derivative can be a single compound as shown in (2), or a mixture of two or more compounds as shown in (2). When the amino polyethylene glycol derivative is a mixture, the n and / or R1 in the structural formulas of the different compounds are different.

[0040] In step S1, cyanuric chloride undergoes two condensation reactions sequentially with two raw materials to prepare a stilbene triazine molecular skeleton. The two raw materials are 4,4′-diaminostilbene-2,2′-disulfonic acid and an aromatic amine. Understandably, the ice-water mixture of cyanuric chloride can undergo a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid, followed by a second condensation reaction with the aromatic amine; alternatively, it can undergo a first condensation reaction with the aromatic amine, followed by a second condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid.

[0041] Specifically, the aromatic amine is selected from aniline, aminobenzenesulfonic acid, or monosodium aniline-2,5-disulfonic acid.

[0042] To improve the efficiency of the condensation reaction, when the aromatic amine is selected from aniline, the ice-water mixture of cyanuric chloride is sequentially condensed with the 4,4′-diaminostilbene-2,2′-disulfonic acid and the aromatic amine.

[0043] In another embodiment, when the aromatic amine is selected from p-aminobenzenesulfonic acid or aniline-2,5-disulfonic acid monosodium salt, the cyanuric chloride ice-water mixture is sequentially condensed with the aromatic amine and the 4,4′-diaminostilbene-2,2′-disulfonic acid.

[0044] Understandably, both the first and second condensation reactions in this invention employ existing techniques in the art, and this invention does not impose any special limitations on them. Specifically, water and ice are added to a flask, and cyanuric chloride is added at 0°C to obtain an ice-water mixture of cyanuric chloride. Then, 4,4′-diaminostilbene-2,2′-disulfonic acid or an aromatic amine is added dropwise to carry out the first condensation reaction. After the first condensation reaction is completed, another raw material is added to carry out the second condensation reaction.

[0045] To further improve the efficiency of the condensation reaction, in the first condensation reaction step, it is preferable to adjust the pH of the system to ≤5 and the temperature to ≤5℃.

[0046] To further improve the efficiency of the condensation reaction, in the second condensation reaction step, it is preferable to adjust the pH of the system to ≤9 and the temperature to ≤60℃.

[0047] In one embodiment, the pH of the system is adjusted using a sodium carbonate solution in the first condensation reaction and the second condensation reaction steps.

[0048] In one embodiment, the molar ratio of the cyanuric chloride to the 4,4′-diaminostilbene-2,2′-disulfonic acid and the aromatic amine is 1:(0.45-0.5):(0.95-1.05).

[0049] Preferably, the molar ratio of the cyanuric chloride to the 4,4′-diaminostilbene-2,2′-disulfonic acid and the aromatic amine is 1:(0.49~0.50):(0.98~1.01).

[0050] Preferably, the structural formula of the stilbene triazine molecular skeleton is shown in formula (3), formula (4), formula (5) or formula (6).

[0051]

[0052] In step S2, the stilbene triazine molecular backbone is condensed with an amino polyethylene glycol derivative to prepare a fluorescent whitening agent with a special molecular structure, which effectively improves the molecular stability and steric hindrance of the fluorescent whitening agent, thereby improving its dispersibility and lightfastness.

[0053] In one embodiment, the molar ratio of the stilbene triazine molecular backbone to the amino polyethylene glycol derivative is 1:2.1 to 1:2.5.

[0054] Specifically, in the third condensation reaction step, the pH of the system is adjusted to 9-10, the temperature is 90℃-103℃, and the system is refluxed for 4-5 hours.

[0055] Preferably, in the third condensation reaction step, the pH of the system is adjusted to 9-10, the temperature is 95℃-102℃, and the system is refluxed for 4-5 hours.

[0056] Specifically, the pH of the system is adjusted using a liquid alkali solution.

[0057] It should be noted that the present invention does not have special requirements for the pressure of the first condensation reaction, the second condensation reaction, and the third condensation reaction. Those skilled in the art can select the appropriate pressure based on actual needs such as product quality, production efficiency, and production cost. In order to reduce production costs and simplify process conditions, the pressure of the first condensation reaction, the second condensation reaction, and the third condensation reaction in the present invention is preferably atmospheric pressure.

[0058] The present invention also provides the application of the fluorescent whitening agent as described above in paper fiber whitening, textile fiber whitening and coating whitening.

[0059] The following specific examples will further illustrate the fluorescent whitening agent, its preparation method, and its application. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified, specific conditions in the examples were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used, unless otherwise specified, are all commercially available conventional products.

[0060] Example 1

[0061] In a four-necked flask, water and ice were added. At 0°C, 10g of cyanuric chloride was added, followed by the dropwise addition of 100g of a 10% solution of 4,4′-diaminostilbene-2,2′-disulfonic acid to initiate the first condensation reaction. The temperature was controlled to be ≤5°C, and a 10% solution of sodium carbonate was added to control the pH to be ≤5. After the first condensation reaction was completed, 5g of aniline was added to initiate the second condensation reaction. The temperature was controlled to be ≤30°C, and a 10% solution of sodium carbonate was added to control the pH to be ≤9. The stilbene triazine molecular skeleton was obtained, and its structural formula is shown in formula (3-1). The molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid, and aniline was 1:0.49:1.01.

[0062] The amino-polyethylene glycol derivative, with the structural formula shown in formula (2-1), is then added. The molar ratio of the stilbene triazine molecular backbone to the amino-polyethylene glycol derivative is 1:2.2. Simultaneously, a 32% alkaline solution is added dropwise to control the pH at 9–10. The mixture is then refluxed at 100°C for 4 hours to obtain the fluorescent whitening agent, with the structural formula shown in formula (1-1).

[0063]

[0064] Example 2

[0065] In a four-necked flask, water and ice were added. At 0°C, 10g of cyanuric chloride was added, followed by the dropwise addition of 9.35g of p-aminobenzenesulfonic acid to initiate the first condensation reaction. The temperature was controlled at ≤5°C, and a 10% sodium carbonate solution was added to control the pH at ≤4. After the first condensation reaction was completed, 98g of a 10% solution of 4,4′-diaminostilbene-2,2′-disulfonic acid was added to initiate the second condensation reaction. The temperature was controlled at ≤60°C, and a 10% sodium carbonate solution was added to control the pH at ≤7. The stilbene triazine molecular skeleton was obtained, and its structural formula is shown in formula (4-1). The molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid, and p-aminobenzenesulfonic acid was 1:0.49:1.0.

[0066] The amino-polyethylene glycol derivative, with its structural formula shown in formula (2-2), is then added. The molar ratio of the stilbene triazine molecular backbone to the amino-polyethylene glycol derivative is 1:2.1. Simultaneously, a 32% alkaline solution is added dropwise to control the pH at 9–10. The mixture is then refluxed at 100°C for 4 hours to obtain the fluorescent whitening agent, with its structural formula shown in formula (1-2).

[0067]

[0068] Example 3

[0069] In a four-necked flask, water and ice were added. At 0°C, 10g of cyanuric chloride was added, followed by the dropwise addition of 9.35g of p-aminobenzenesulfonic acid to initiate the first condensation reaction. The temperature was controlled to be ≤5°C, and a 10% sodium carbonate solution was added to control the pH to be ≤4. After the first condensation reaction was completed, 98g of a 10% solution of 4,4′-diaminostilbene-2,2′-disulfonic acid was added to initiate the second condensation reaction. The temperature was controlled to be ≤60°C, and a 10% sodium carbonate solution was added to control the pH to be ≤7. The stilbene triazine molecular skeleton was obtained, and its structural formula is shown in formula (4-1). The molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid, and p-aminobenzenesulfonic acid was 1:0.5:1.0.

[0070] The amino-polyethylene glycol derivative, with its structural formula shown in formula (2-3), is then added. The molar ratio of the stilbene triazine molecular backbone to the amino-polyethylene glycol derivative is 1:2.5. Simultaneously, a 32% alkaline solution is added dropwise to control the pH at 9-10. The mixture is then refluxed at 100°C for 4 hours to obtain the fluorescent whitening agent, with its structural formula shown in formula (1-3).

[0071]

[0072] Example 4

[0073] In a four-necked flask, water and ice were added. At 0°C, 10g of cyanuric chloride was added, followed by the dropwise addition of 14.9g of monosodium aniline-2,5-disulfonic acid for the first condensation reaction. The temperature was controlled at ≤5°C, and a 10% sodium carbonate solution was added to control the pH at ≤3. After the first condensation reaction was completed, 98g of 4,4′-diaminostilbene-2,2′-disulfonic acid was added for the second condensation reaction. The temperature was controlled at ≤60°C, and a 10% sodium carbonate solution was added to control the pH at ≤6. The stilbene triazine molecular skeleton was obtained, and its structural formula is shown in formula (5-1). The molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid, and monosodium aniline-2,5-disulfonic acid was 1:0.49:1.0.

[0074] The amino-polyethylene glycol derivative, with its structural formula shown in formula (2-4), is then added. The molar ratio of the stilbene triazine molecular backbone to the amino-polyethylene glycol derivative is 1:2.2. Simultaneously, a 32% alkaline solution is added dropwise to control the pH at 9-10. The mixture is then refluxed at 100°C for 3 hours to obtain the fluorescent whitening agent, with its structural formula shown in formula (1-4).

[0075]

[0076]

[0077] Example 5

[0078] The difference between Example 5 and Example 1 is that a first amino polyethylene glycol derivative (with structural formulas shown in Formulas 2-5) and a second amino polyethylene glycol derivative (with structural formulas shown in Formulas 2-6) are simultaneously added to undergo a condensation reaction with the stilbene triazine molecular backbone. The resulting fluorescent whitening agent has the structural formulas shown in Formulas (1-5), (1-6), and (1-7).

[0079]

[0080]

[0081] Example 6

[0082] The difference between Example 6 and Example 1 is that a third amino polyethylene glycol derivative (with the structural formula shown in Formula 2-1) and a fourth amino polyethylene glycol derivative (with the structural formula shown in Formula 2-7) are simultaneously added to undergo a condensation reaction with the stilbene triazine molecular backbone. The resulting fluorescent whitening agent has the structural formulas shown in Formulas (1-1), (1-8), and (1-9).

[0083]

[0084] Comparative Example 1

[0085] The difference between Comparative Example 1 and Example 1 is that the obtained stilbene triazine molecular skeleton was subjected to a condensation reaction with ethanolamine, followed by acid precipitation, kneading, and drying. The resulting fluorescent whitening agent has the structural formula shown in formula (7).

[0086]

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 2 is that the obtained stilbene triazine molecular skeleton was subjected to a condensation reaction with diethanolamine, followed by acid precipitation, kneading, and drying. The resulting fluorescent whitening agent has the structural formula shown in formula (8).

[0089]

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Example 4 is that the obtained stilbene triazine molecular skeleton was subjected to a condensation reaction with diethylamine, and then concentrated by nanofiltration. The resulting fluorescent whitening agent has the structural formula shown in formula (9).

[0092]

[0093] Comparative Example 4

[0094] The difference between Comparative Example 4 and Example 1 is that the obtained stilbene triazine molecular skeleton was subjected to a condensation reaction with a compound as shown in Formula (10), and the resulting fluorescent whitening agent has the structural formula shown in Formula (11).

[0095]

[0096] All the fluorescent whitening agents prepared in the examples and comparative examples were applied to the surface of paper. The concentration of each fluorescent whitening agent was the highest yellowing point concentration (the concentration of fluorescent whitening agent used when the paper reaches the highest whiteness). After drying, the Ganz whiteness (CIE whiteness) of the paper was tested using Datacolor 650, and the CIE whiteness of the paper was also tested after 1 hour of ultraviolet light irradiation.

[0097] The test results of the fluorescent whitening agents prepared in all examples and comparative examples are shown in Tables 1 to 3.

[0098] Table 1

[0099]

[0100]

[0101] Table 2

[0102]

[0103] Table 3

[0104]

[0105] As shown in Tables 1-3, with the same stilbene triazine molecular skeleton, the highest yellowing point concentration of the fluorescent whitening agents prepared in the examples was higher than that of the fluorescent whitening agents prepared in the comparative examples. Furthermore, at the highest yellowing point concentration, the CIE whiteness of the paper was higher. Therefore, the fluorescent whitening agent of this invention has good dispersibility, and the molecules are less prone to aggregation leading to quenching, resulting in a better whitening effect. Simultaneously, after 1 hour of UV irradiation, the fluorescent whitening agent prepared in the examples still exhibited a good whitening effect, while the whiteness of the paper prepared in the comparative examples decreased significantly after 1 hour of UV irradiation. Therefore, the fluorescent whitening agent of this invention has better lightfastness. In summary, the fluorescent whitening agent provided by this invention has good dispersibility and lightfastness, thereby improving the whitening effect and practicality of the fluorescent whitening agent, and has a wide range of applications and a promising market prospect.

[0106] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A fluorescent whitening agent, characterized in that, The structural formula of the fluorescent whitening agent is shown in formula (1-4). 。 2. A method for preparing the fluorescent whitening agent as described in claim 1, characterized in that, The preparation method includes the following steps: A first condensation reaction is carried out between a cyanuric chloride-ice-water mixture and an aromatic amine, followed by a second condensation reaction with the addition of 4,4′-diaminostilbene-2,2′-disulfonic acid to obtain a stilbene triazine molecular skeleton. The molar ratio of the cyanuric chloride to the 4,4′-diaminostilbene-2,2′-disulfonic acid and the aromatic amine is 1:(0.45~0.50):(0.95~1.05). The aromatic amine is selected from the monosodium salt of aniline-2,5-disulfonic acid. The structural formula of the stilbene triazine molecular skeleton is shown in formula (5-1). ； The stilbene triazine molecular backbone is subjected to a third condensation reaction with an amino polyethylene glycol derivative to obtain the fluorescent whitening agent, wherein the molar ratio of the stilbene triazine molecular backbone to the amino polyethylene glycol derivative is 1:2.1 to 1:2.5, and the structural formula of the amino polyethylene glycol derivative is shown in formula (2-4). ; In the first condensation reaction step, the pH of the system is adjusted to ≤5 and the temperature to ≤5℃ using a soda ash solution; In the second condensation reaction step, the pH of the system is adjusted to ≤9 and the temperature to ≤60℃ using a sodium carbonate solution; In the third condensation reaction step, the pH of the system is adjusted to 9-10 using a liquid alkali solution, the temperature is adjusted to 90℃-103℃, and the system is refluxed for 3-5 hours.

3. The application of the fluorescent whitening agent as described in claim 1 in paper fiber whitening, textile fiber whitening, and coating whitening.

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