Fluorescent whitening agent as well as preparation method and application thereof

Abstract

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

Description

Technical Field

[0001] The invention relates to the technical field of fluorescent whitening agents, in particular to a fluorescent whitening agent and a preparation method and application thereof. Background Art

[0002] As an important fine chemical product, fluorescent whitening agent has a wide range of applications and good market prospects in industry. At present, a large amount of fluorescent whitening agent is mainly added to paper, cotton cloth, and coating to improve whiteness. However, the existing fluorescent whitening agent has low dispersibility. When the concentration of fluorescent whitening agent is high, the molecules will overlap and cause the quenching of the fluorescent whitening agent. At the same time, the light resistance of the existing fluorescent whitening agent is poor, which affects the whitening effect. Therefore, a fluorescent whitening agent with high dispersibility and light resistance is urgently needed to improve the whitening effect and practicality of the fluorescent whitening agent. Summary of the invention

[0003] Based on this, it is necessary to provide a fluorescent whitening agent and its preparation method and application to address the above problems. The fluorescent whitening agent provided by the present invention has good dispersibility and light resistance, 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 brightener, the structural formula of which is shown in formula (1),

[0005]

[0006] In formula (1), n ​​and m are each independently selected from a natural number 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, wherein M is selected from -H, -Na or -K.

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

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

[0009] A mixture of cyanuric chloride and ice water is subjected to a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid, and then aromatic amine is added to carry out a second condensation reaction to obtain a stilbene triazine molecular skeleton;

[0010] Alternatively, a mixture of cyanuric chloride and water is subjected to a first condensation reaction with aromatic amine, and then 4,4′-diaminostilbene-2,2′-disulfonic acid is added to conduct a second condensation reaction to obtain a stilbene triazine molecular skeleton;

[0011] The distyryl triazine molecular skeleton is subjected to a third condensation reaction with an amino polyethylene glycol derivative to obtain the fluorescent whitening agent, wherein the amino polyethylene glycol derivative has a structural formula as shown in formula (2). In formula (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 carrying out a first condensation reaction of a mixture of cyanuric chloride and ice water with 4,4′-diaminostilbene-2,2′-disulfonic acid and then adding aromatic amine to carry out a second condensation reaction, the aromatic amine is selected from aniline;

[0014] Alternatively, in the step of carrying out a first condensation reaction of the ice-water mixture of cyanuric chloride and aromatic amine and then adding 4,4'-diaminostilbene-2,2'-disulfonic acid to carry out a second condensation reaction, the aromatic amine is selected from p-aminobenzenesulfonic acid or aniline-2,5-disulfonic acid monosodium salt.

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

[0016]

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

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

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

[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° C.-103° C., and refluxed for 3 h-5 h.

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

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

[0023] The invention discloses an application of the fluorescent brightener as described above in paper fiber whitening, textile fiber whitening and coating whitening.

[0024] The above-mentioned fluorescent whitening agent has a special molecular structure. On the one hand, the fluorescent whitening agent has high stability, and the ether bonds in the fluorescent whitening agent molecules can form strong hydrogen bonds with the hydroxyl groups in the fiber, effectively improving the light resistance and practicality of the fluorescent whitening agent; on the other hand, the steric hindrance between the fluorescent whitening agent molecules is large, and the molecules are not easy to aggregate, which is conducive to improving the dispersion and reducing the quenching of the fluorescent whitening agent molecules, thereby improving the whitening effect and light resistance of the fluorescent whitening agent.

[0025] Therefore, the fluorescent whitening agent provided by the present invention has good dispersibility and light resistance, thereby improving the whitening effect and practicality of the fluorescent whitening agent, and has a wide range of application fields and good market prospects. DETAILED DESCRIPTION

[0026] For ease of understanding of the present invention, the present invention 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. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those generally understood by those skilled in the art of the present invention. The terms used herein in the specification of the present invention are only for the purpose of describing specific implementation methods or embodiments, and are not intended to limit the present invention. The optional scope of the term "and / or" used herein includes any one of two or more related listed items, and also includes any and all combinations of related listed items, and the combinations include any two related listed items, any more related listed items, or all related listed items.

[0028] The fluorescent whitening agent provided by the present invention has a structural formula as shown in formula (1):

[0029]

[0030] In formula (1), n ​​and m are each independently selected from a natural number 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, wherein M is selected from -H, -Na or -K.

[0031] The above-mentioned fluorescent whitening agent has a special molecular structure. On the one hand, the fluorescent whitening agent has high stability, and the ether bonds in the fluorescent whitening agent molecules can be oriented after drying. The lone pair of electrons of the oxygen atom is exposed to the outside, and can form upper and lower hydrogen bonds with the hydroxyl groups in cellulose, effectively improving the light resistance and practicality of the fluorescent whitening agent; on the other hand, the steric hindrance between the fluorescent whitening agent molecules is large, and the molecules are not easy to aggregate, which is conducive to improving the dispersibility and reducing the quenching of the fluorescent whitening agent molecules, thereby improving the whitening effect and light resistance of the fluorescent whitening agent.

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

[0033] Preferably, the n and the m are each independently selected from natural numbers ranging from 2 to 40, which is beneficial to further improve the dispersibility and light resistance 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 the n and the m may be the same or different.

[0034] More preferably, the n and the 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, subjecting a mixture of cyanuric chloride and ice water to a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid, and then adding aromatic amine to a second condensation reaction to obtain a stilbene triazine molecular skeleton;

[0037] Alternatively, a mixture of cyanuric chloride and water is subjected to a first condensation reaction with aromatic amine, and then 4,4′-diaminostilbene-2,2′-disulfonic acid is added to conduct a second condensation reaction to obtain a stilbene triazine molecular skeleton;

[0038] S2, subjecting the distyryl triazine molecular skeleton to a third condensation reaction with an amino polyethylene glycol derivative to obtain the fluorescent whitening agent, wherein the amino polyethylene glycol derivative has a structural formula as shown in formula (2), In formula (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 aminopolyethylene 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 aminopolyethylene glycol derivative is a mixture, n and / or R1 in the structural formulas of the compounds are different.

[0040] In step S1, cyanuric chloride is subjected to two condensation reactions in sequence with two raw materials to prepare a stilbene triazine molecular skeleton, wherein the two raw materials are 4,4′-diaminostilbene-2,2′-disulfonic acid and aromatic amine. It can be understood that the ice-water mixture of cyanuric chloride can first undergo a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid and then undergo a second condensation reaction with aromatic amine, or can first undergo a first condensation reaction with aromatic amine and then undergo a second condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid.

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

[0042] In order 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 subjected to condensation reaction 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 ice-water mixture of cyanuric chloride is sequentially subjected to condensation reaction with the aromatic amine and the 4,4′-diaminostilbene-2,2′-disulfonic acid.

[0044] It can be understood that the first condensation reaction and the second condensation reaction in the present invention both adopt the existing technology in the art, and the present invention has no special restrictions on this. Specifically, water and ice are added to a flask, and cyanuric chloride is added at a temperature of 0°C to obtain an ice-water mixture of cyanuric chloride, and then 4,4'-diaminobenzylbenzene-2,2'-disulfonic acid or aromatic amine is added dropwise to carry out a first condensation reaction. After the first condensation reaction is completed, another raw material is added to carry out a second condensation reaction.

[0045] In order to further improve the efficiency of the condensation reaction, in the first condensation reaction step, it is preferred to adjust the pH of the system to ≤ 5 and the temperature to ≤ 5°C.

[0046] In order to further improve the efficiency of the condensation reaction, in the second condensation reaction step, it is preferred to adjust the pH of the system to ≤ 9 and the temperature to ≤ 60°C.

[0047] In one embodiment, in the first condensation reaction and the second condensation reaction steps, a pure alkali solution is used to adjust the pH of the system.

[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 distyryl triazine molecular skeleton is as shown in Formula (3), Formula (4), Formula (5) or Formula (6),

[0051]

[0052] In step S2, a distyryl triazine molecular skeleton is subjected to a condensation reaction 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 the dispersibility and light resistance.

[0053] In one embodiment, the molar ratio of the distyryl triazine molecular skeleton 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° C.-103° C., and reflux is performed for 4 h-5 h.

[0055] Preferably, in the third condensation reaction step, the pH of the system is adjusted to 9-10, the temperature is 95° C.-102° C., and reflux is performed for 4 h-5 h.

[0056] Specifically, a liquid alkali solution is used to adjust the pH of the system.

[0057] It should be noted that the present invention has no 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 make choices 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 normal pressure.

[0058] The present invention also provides a use of the fluorescent whitening agent as described above in whitening paper fibers, textile fibers and coatings.

[0059] Hereinafter, the fluorescent whitening agent and its preparation method and application will be further described by the following specific examples. However, it will be understood by those skilled in the art that the following examples are only used to illustrate the present invention and should not be regarded as limiting the scope of the present invention. If no specific conditions are specified in the examples, the conditions are carried out according to conventional conditions or the conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be obtained commercially.

[0060] Example 1

[0061] In a four-necked flask, add water and ice, add 10g of cyanuric chloride at 0°C, then add 100g of 4,4′-diaminostilbene-2,2′-disulfonic acid solution (concentration of 10%) dropwise to carry out a first condensation reaction, control the temperature to ≤5°C, and add soda ash solution (concentration of 10%) dropwise to control the pH to ≤5. After the first condensation reaction is completed, add 5g of aniline for a second condensation reaction, control the temperature to ≤30°C, and add soda ash solution (concentration of 10%) dropwise to control the pH to ≤9 to obtain a distilbene triazine molecular skeleton, whose structural formula is shown in formula (3-1), wherein the molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid and aniline is 1:0.49:1.01.

[0062] Continue to add aminopolyethylene glycol derivatives, the structural formula of which is shown in formula (2-1), wherein the molar ratio of distyryl triazine molecular skeleton to aminopolyethylene glycol derivative is 1:2.2, and at the same time, add liquid alkali solution (concentration of 32%) dropwise to control the pH to 9-10, reflux at 100° C. for 4 hours to obtain a fluorescent whitening agent, the structural formula of which is shown in formula (1-1),

[0063]

[0064] Example 2

[0065] In a four-necked flask, add water and ice, add 10g of cyanuric chloride at 0°C, then add 9.35g of p-aminobenzenesulfonic acid dropwise for a first condensation reaction, control the temperature to ≤5°C, and add soda ash solution (concentration of 10%) dropwise to control the pH to ≤4. After the first condensation reaction is completed, add 98g of 4,4′-diaminostilbene-2,2′-disulfonic acid solution (concentration of 10%) for a second condensation reaction, control the temperature to ≤60°C, and add soda ash solution (concentration of 10%) dropwise to control the pH to ≤7 to obtain a distilbene triazine molecular skeleton, whose structural formula is shown in formula (4-1), wherein the molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid and p-aminobenzenesulfonic acid is 1:0.49:1.0.

[0066] Continue to add amino polyethylene glycol derivatives, the structural formula of which is shown in formula (2-2), wherein the molar ratio of the distyryl triazine molecular skeleton to the amino polyethylene glycol derivative is 1:2.1, and at the same time, add a liquid alkali solution (concentration of 32%) to control the pH to 9-10, reflux at 100° C. for 4 hours to obtain a fluorescent whitening agent, the structural formula of which is shown in formula (1-2),

[0067]

[0068] Example 3

[0069] In a four-necked flask, add water and ice, add 10g of cyanuric chloride at 0°C, then add 9.35g of p-aminobenzenesulfonic acid dropwise for a first condensation reaction, control the temperature to ≤5°C, and add soda ash solution (concentration of 10%) dropwise to control the pH to ≤4. After the first condensation reaction is completed, add 98g of 4,4′-diaminostilbene-2,2′-disulfonic acid solution (concentration of 10%) for a second condensation reaction, control the temperature to ≤60°C, and add soda ash solution (concentration of 10%) dropwise to control the pH to ≤7 to obtain a distilbene triazine molecular skeleton, whose structural formula is shown in formula (4-1), wherein the molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid and p-aminobenzenesulfonic acid is 1:0.5:1.0.

[0070] Continue to add aminopolyethylene glycol derivatives, the structural formula of which is shown in formula (2-3), wherein the molar ratio of the distyryl triazine molecular skeleton to the aminopolyethylene glycol derivative is 1:2.5, and at the same time, add a liquid alkali solution (concentration of 32%) to control the pH to 9-10, reflux at 100° C. for 4 hours to obtain a fluorescent whitening agent, the structural formula of which is shown in formula (1-3),

[0071]

[0072] Example 4

[0073] In a four-necked flask, add water and ice, add 10 g of cyanuric chloride at 0°C, then add 14.9 g of aniline-2,5-disulfonic acid monosodium salt dropwise for a first condensation reaction, control the temperature to ≤5°C, and add a soda ash solution (10% concentration) dropwise to control the pH to ≤3. After the first condensation reaction is completed, add 98 g of 4,4′-diaminostilbene-2,2′-disulfonic acid for a second condensation reaction, control the temperature to ≤60°C, and add a soda ash solution (10% concentration) dropwise to control the pH to ≤6 to obtain a distilbene triazine molecular skeleton, the structural formula of which is shown in formula (5-1), wherein the molar ratio of cyanuric chloride, 4,4′-diaminostilbene-2,2′-disulfonic acid and aniline-2,5-disulfonic acid monosodium salt is 1:0.49:1.0.

[0074] Continue to add aminopolyethylene glycol derivatives, whose structural formula is shown in formula (2-4), wherein the molar ratio of distyryl triazine molecular skeleton to aminopolyethylene glycol derivative is 1:2.2, and at the same time, add liquid alkali solution (concentration of 32%) dropwise to control the pH to 9-10, reflux at 100° C. for 3 hours to obtain a fluorescent whitening agent, whose structural formula is shown in formula (1-4),

[0075]

[0076]

[0077] Example 5

[0078] The difference between Example 5 and Example 1 is that the first amino polyethylene glycol derivative (whose structural formula is shown in Formula 2-5) and the second amino polyethylene glycol derivative (whose structural formula is shown in Formula 2-6) are added simultaneously to carry out condensation reaction with the distyryl triazine molecular skeleton, and the structural formulas of the obtained fluorescent whitening agents are shown in Formula (1-5), Formula (1-6), and Formula (1-7).

[0079]

[0080]

[0081] Example 6

[0082] The difference between Example 6 and Example 1 is that a third amino polyethylene glycol derivative (whose structural formula is shown in Formula 2-1) and a fourth amino polyethylene glycol derivative (whose structural formula is shown in Formula 2-7) are added simultaneously to carry out condensation reaction with the distyryl triazine molecular skeleton, and the structural formulas of the obtained fluorescent whitening agents are shown in Formula (1-1), Formula (1-8), and Formula (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 is subjected to a condensation reaction with ethanolamine, and then kneaded by acid precipitation and dried to obtain a fluorescent whitening agent having a structural formula as shown in Formula (7):

[0086]

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 2 is that the obtained distyryl triazine molecular skeleton is subjected to a condensation reaction with diethanolamine, and then kneaded by acid precipitation and dried to obtain a fluorescent whitening agent having a structural formula as shown in Formula (8):

[0089]

[0090] Comparative Example 3

[0091] The difference between Comparative Example 3 and Example 4 is that the obtained distyryl triazine molecular skeleton is subjected to a condensation reaction with diethylamine and concentrated by nanofiltration. The structural formula of the obtained fluorescent whitening agent is shown in Formula (9):

[0092]

[0093] Comparative Example 4

[0094] The difference between Comparative Example 4 and Example 1 is that the obtained distyryl triazine molecular skeleton is subjected to a condensation reaction with the compound shown in formula (10), and the structure of the obtained fluorescent whitening agent is shown in formula (11).

[0095]

[0096] The fluorescent brighteners prepared in all the embodiments and comparative examples were applied on the surface of paper. The applied concentration of each fluorescent brightener was the highest yellowing point concentration (the concentration of the fluorescent brightener used when the paper reached 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 tested after irradiation with ultraviolet light for 1 hour.

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

[0098] Table 1

[0099]

[0100]

[0101] Table 2

[0102]

[0103] Table 3

[0104]

[0105] According to the results of Tables 1 to 3, when the molecular skeleton of the diphenylethylene triazine group is the same, the highest yellowing point concentration of the fluorescent whitening agent obtained in the embodiment is higher than the highest yellowing point concentration of the fluorescent whitening agent obtained in the comparative example, and at the highest yellowing point concentration, the CIE whiteness of the paper is higher. Therefore, the fluorescent whitening agent of the present invention has good dispersibility, and the molecules are not easy to agglomerate and cause quenching, and have a good whitening effect. At the same time, after 1 hour of ultraviolet light irradiation, the fluorescent whitening agent obtained in the embodiment still has a good whitening effect, while the whiteness of the paper obtained in the comparative example is significantly reduced after 1 hour of ultraviolet light irradiation. Therefore, the fluorescent whitening agent of the present invention has good light resistance. In summary, the fluorescent whitening agent provided by the present invention has good dispersibility and light resistance, thereby improving the whitening effect and practicality of the fluorescent whitening agent, and has a wide range of applications and good market prospects.

[0106] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described 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 above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A fluorescent whitening agent, characterized in that: The structural formula of the fluorescent whitening agent is shown in formula (1), In formula (1), n ​​and m are each independently selected from a natural number 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, wherein M is selected from -H, -Na or -K.

2. The fluorescent whitening agent according to claim 1, characterized in that The n and the m are each independently selected from natural numbers of 5-20.

3. A method for preparing a fluorescent whitening agent as claimed in claim 1 or 2, characterized in that: The preparation method comprises the following steps: A mixture of cyanuric chloride and ice water is subjected to a first condensation reaction with 4,4′-diaminostilbene-2,2′-disulfonic acid, and then aromatic amine is added to carry out a second condensation reaction to obtain a stilbene triazine molecular skeleton; Alternatively, a mixture of cyanuric chloride and water is subjected to a first condensation reaction with aromatic amine, and then 4,4′-diaminostilbene-2,2′-disulfonic acid is added to conduct a second condensation reaction to obtain a stilbene triazine molecular skeleton; The distyryl triazine molecular skeleton is subjected to a third condensation reaction with an amino polyethylene glycol derivative to obtain the fluorescent whitening agent, wherein the amino polyethylene glycol derivative has a structural formula as shown in formula (2). In formula (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.

4. The method for preparing a fluorescent whitening agent according to claim 3, characterized in that: The molar ratio of the cyanuric chloride to the 4,4′-diaminobenzylbenzene-2,2′-disulfonic acid and the aromatic amine is 1:(0.45-0.50):(0.95-1.05).

5. The method for preparing a fluorescent whitening agent according to claim 3, characterized in that: In the step of carrying out a first condensation reaction of a mixture of cyanuric chloride and ice water with 4,4′-diaminostilbene-2,2′-disulfonic acid, and then adding aromatic amine to carry out a second condensation reaction, the aromatic amine is selected from aniline; Alternatively, in the step of carrying out a first condensation reaction of the ice-water mixture of cyanuric chloride and aromatic amine and then adding 4,4'-diaminostilbene-2,2'-disulfonic acid to carry out a second condensation reaction, the aromatic amine is selected from p-aminobenzenesulfonic acid or aniline-2,5-disulfonic acid monosodium salt.

6. The method for preparing a fluorescent whitening agent according to claim 3, characterized in that: The structural formula of the distyryl triazine molecular skeleton is shown in Formula (3), Formula (4), Formula (5) or Formula (6), 7. The method for preparing a fluorescent whitening agent according to claim 3, characterized in that: The molar ratio of the distyryl triazine molecular skeleton to the amino polyethylene glycol derivative is 1:2.1 to 1:2.

5.

8. The method for preparing a fluorescent whitening agent according to claim 3, characterized in that: In the first condensation reaction step, the pH of the system is adjusted to ≤5 and the temperature is ≤5°C; And / or, in the second condensation reaction step, the pH of the system is adjusted to ≤ 9 and the temperature is ≤ 60° C.; And / or, in the third condensation reaction step, the pH of the system is adjusted to 9-10, the temperature is adjusted to 90° C.-103° C., and refluxed for 3 h-5 h.

9. The method for preparing a fluorescent whitening agent according to claim 8, characterized in that: In the first condensation reaction and the second condensation reaction steps, a pure alkali solution is used to adjust the pH of the system; And / or, in the third condensation reaction step, a liquid alkali solution is used to adjust the pH of the system.

10. Use of the fluorescent whitening agent according to claim 1 or 2 in whitening paper fibers, textile fibers and coatings.

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