A stable acid-resistant brightener and its preparation process

Abstract

The invention relates to the field of D21H21 / 30, and in particular to a stable acid-resistant brightener and a preparation process thereof. The preparation raw materials at least include cyanuric chloride, a sulfonic acid compound, an amine compound and an amino acid. Glycine and glutamic acid are added by design to carry out a condensation reaction, and a liquid fluorescent brightener containing an asymmetric structure is obtained after the reaction, thereby greatly improving the storage stability of the liquid fluorescent brightener. Meanwhile, the liquid fluorescent brightener with a symmetrical structure and the liquid fluorescent brightener with an asymmetric structure generated after the reaction have a composite whitening effect, and the optical behaviors generated by the liquid fluorescent brighteners of different components do not interfere with each other, thereby greatly improving the whitening effect of the stable acid-resistant brightener, solving the problem that the surface of the obtained paper is dark and the whiteness is not high in the process of applying the fluorescent brightener to papermaking, and ensuring the whiteness, water solubility and anti-cation interference ability of the product.

Description

Technical Field

[0001] The invention relates to the field of D21H21 / 30, in particular to a stable acid-resistant brightener and a preparation process thereof. Background Art

[0002] Fluorescent whitening agents have the function of brightening and brightening, and are widely used in the fields of papermaking, textile coatings, etc. Among them, bistriazine amino diphenylethylene type fluorescent whitening agents are widely used in the fields of papermaking, printing and dyeing due to their high cost performance and good whitening performance. In recent years, due to the continuous increase in paper mills and printing and dyeing factories, the demand for fluorescent whitening agents has increasingly tended to have high whitening performance, small dosage and low cost.

[0003] Surface sizing is an indispensable step in the papermaking process. Glue is applied when the paper has a certain strength and the surface is not completely dry, so as to achieve the whitening effect of the paper. However, the price of the fluorescent brightener hexasulfonic acid in the prior art is relatively high. Therefore, it is of great significance to prepare a fluorescent brightener for high-white paper production to solve the problem of the expensive price of the existing fluorescent brightener.

[0004] Chinese patent CN104312197A discloses a method for preparing fluorescent whitening agent hexasulfonic acid using cyanuric chloride, aniline-2,5-disulfonic acid, 4,4-diaminostilbene-2,2-disulfonic acid and diethanolamine as raw materials. The method has high whiteness and stable storage when applied to papermaking, but has high cost of use, which is not conducive to cost saving.

[0005] Chinese patent CN101429344A discloses a whitening agent for paper surface sizing. The fluorescent whitening agent hexasulfonic acid is prepared by using cyanuric chloride, aniline-2,4-disulfonic acid, aniline-2,5-disulfonic acid, 4,4-diaminostilbene-2,2-disulfonic acid and morpholine as raw materials. The whiteness and yield of the obtained product are greatly improved, the storage stability is improved, and the yellowing point is improved. However, the introduction of the morpholine group is not conducive to environmental protection.

[0006] Aiming at the problem that the fluorescent brightener prepared in the prior art is not stable enough, so that amine substances are precipitated or stink, and the surface of the obtained paper is dark and the whiteness is not high during the application in papermaking, the present invention designs a preparation process of a stable acid-resistant brightener, which has simple process, low production cost, high product whiteness, good whitening effect, strong water solubility and anti-cation interference ability, meets the production and application requirements of high white paper, and has high market application value. Summary of the invention

[0007] In order to solve the above problems, the present invention provides a stable acid-resistant brightener, the raw materials for preparing the stable acid-resistant brightener include at least cyanuric chloride, sulfonic acid compounds, amine compounds and amino acids.

[0008] As a preferred technical solution, the sulfonic acid substance is selected from one or a combination of 4,4'-diaminostilbene-2,2'-disulfonic acid, p-aminobenzenesulfonic acid, sodium p-aminobenzenesulfonate, aniline-2,5-bissulfonic acid monosodium salt, and aniline-2,5-bissulfonic acid;

[0009] As a preferred technical solution, the amine compound is selected from one or a combination of aniline, diethanolamine, diisopropanolamine, and diethylamine;

[0010] As a preferred technical solution, the amino acid is selected from one or a combination of glycine, glutamic acid, alanine, arginine, serine, and leucine; preferably, the amino acid is a mixture of glutamic acid and glycine; preferably, the molar ratio of glutamic acid to glycine is (0-1): (0.1-1.2);

[0011] The inventors found in the process of exploration that in the traditional production process of liquid fluorescent whitening agent, diethanolamine or diethylamine is used to carry out the third step condensation reaction at high temperature to generate a liquid fluorescent whitening agent with a symmetrical structure, but the storage stability of this liquid fluorescent whitening agent is insufficient, and after a short period of storage, the whitening agent will precipitate or stink. Based on the system of the present invention, by designing the addition of amino acids for the third step condensation reaction, especially when the introduced amino acid is a mixture of glycine and glutamic acid with a molar ratio of (0-1): (0.1-1.2), a liquid fluorescent whitening agent containing an asymmetric structure is obtained after the reaction, which greatly improves the storage stability of the liquid fluorescent whitening agent. At the same time, the liquid fluorescent whitening agent with a symmetrical structure and the liquid fluorescent whitening agent with an asymmetric structure generated after the reaction have a composite whitening effect, and the optical behaviors generated by the liquid fluorescent whitening agents of different components do not interfere with each other, which greatly improves the whitening effect of the stable acid-resistant whitening agent, solves the problem that the surface of the obtained paper is dark and the whiteness is not high when the fluorescent whitening agent is used in papermaking, and ensures the whiteness, water solubility and anti-cation interference ability of the product. The inventors analyzed that the reason may be that the whitening effect of the fluorescent whitening agent is related to the fluorescence intensity emitted by the whitening agent on paper, and the fluorescence intensity is related to the fluorescence quantum yield. The symmetrical liquid fluorescent whitening agent and the asymmetrical liquid fluorescent whitening agent contained in the system work together. Since they do not interfere with each other's optical behavior, the fluorescence quantum yield of each component and the fluorescence intensity after compounding are improved, thereby improving the whitening effect on paper.

[0012] Another aspect of the present invention provides a preparation process of a stable acid-resistant brightener, which comprises at least the following steps:

[0013] (1) adding cyanuric chloride to an ice-water mixture, and beating to obtain a cyanuric chloride solution;

[0014] (2) adding a sulfonic acid compound, an amine compound, and an amino acid to the pulped cyanuric chloride solution to perform condensation reactions in sequence to obtain a mixed product;

[0015] (3) Desalting and concentrating the mixed product to obtain a stable acid-resistant brightener.

[0016] In the actual research and development, production and application of whitening agents, the inventors found that the selection and dosage of sulfonic acid compounds and amine compounds in the raw materials for preparing whitening agents directly affect the acid resistance, whitening performance and stability of the whitening agent. In the prior art, cyanuric chloride is reacted with sodium p-aminobenzenesulfonate, 4,4'-diaminobenzene-2,2'-disulfonic acid and di-n-propylethanolamine to prepare tetrasulfonic acid, which increases the storage time of the whitening agent to a certain extent. However, the whitening agent is easy to precipitate under acidic conditions, and in the process of being applied to papermaking, there is a problem that the surface of the obtained paper is dark and the whiteness is not high. During the exploration process, the inventors found that by using specific preparation raw materials and controlling the molar ratio of each reaction raw material, on the one hand, each raw material is fully reacted during the reaction, avoiding the influence of raw material residue on subsequent condensation reaction, reducing the generation of by-products, and ensuring product quality; on the other hand, a stable acid-resistant whitening agent containing symmetrical and asymmetrical structures is generated, the whitening effect of the whitening agent is improved, and the acid resistance and stability of the product are ensured.

[0017] As a preferred technical solution, the raw materials for preparing the stable acid-resistant brightener include cyanuric chloride, p-aminobenzenesulfonic acid, 4,4'-diaminostilbene-2,2'-disulfonic acid, diethanolamine, and amino acid; the molar ratio of cyanuric chloride, p-aminobenzenesulfonic acid, 4,4'-diaminostilbene-2,2'-disulfonic acid, diethanolamine, and amino acid is (0.5-1.5): (1-1.5): (0.3-1): (0-1): (0-1);

[0018] The preparation process of the stable acid-resistant brightener comprises at least the following preparation steps:

[0019] S1, subjecting p-aminobenzenesulfonic acid and cyanuric chloride to a first step condensation reaction in the presence of an acid binding agent;

[0020] S2, continue to add 4,4-diaminobenzylbenzene-2,2-disulfonic acid to carry out the second step condensation reaction;

[0021] S3, first adding diethanolamine, and then adding amino acid to carry out the third step condensation reaction to obtain a mixture of symmetrical and asymmetrical liquid fluorescent whitening agents;

[0022] S4. Cooling the mixture obtained in S3 to 60-65° C., and desalting and concentrating the mixture through a nanofiltration membrane to obtain a stable acid-resistant brightener.

[0023] As a preferred technical solution, the first condensation reaction in step S1 specifically comprises the following steps:

[0024] a. Add cyanuric chloride to the ice-water mixture, cool in an ice bath to keep the temperature below 0°C, and beat for 50-70 minutes;

[0025] b. Then add p-aminobenzenesulfonic acid and stir for 50-70 minutes;

[0026] c. Add an acid binding agent to adjust the system pH to 1.5-5, control the temperature to 0-30° C., and maintain this pH for 100-120 minutes to obtain a contraction reaction system containing a contraction product.

[0027] Preferably, the mass ratio of borneol to water in the ice-water mixture is (200-300): (250-350); the mass ratio of cyanuric chloride to the ice-water mixture is (25-35): (500-600);

[0028] Preferably, the molar ratio of p-aminobenzenesulfonic acid to cyanuric chloride is (0.8-1.2):1;

[0029] Preferably, the acid binding agent is selected from one of Na2CO3 solution, NaHCO3 solution and NaOH solution; preferably, the acid binding agent is NaOH solution or Na2CO3 solution with a mass concentration of 15-20%;

[0030] The inventors found in the process of exploration that cyanuric chloride is first added to an ice-water mixture, the temperature is controlled to be below 0°C, and after beating for 50-70 minutes, p-aminobenzenesulfonic acid is added for reaction, and a NaOH solution or Na2CO3 solution with a mass concentration of 15-20% is used as an acid binding agent. On the one hand, it is avoided that the hydrolysis of cyanuric chloride produces by-products that affect its condensation reaction with p-aminobenzenesulfonic acid, resulting in reduced product purity and performance. On the other hand, p-aminobenzenesulfonic acid and cyanuric chloride in a molar ratio of (0.8-1.2):1 are uniformly and fully reacted, avoiding the residual p-aminobenzenesulfonic acid from affecting the second step condensation reaction, reducing the generation of by-products, and ensuring the whitening performance of the product.

[0031] Preferably, the structural formula of the condensed product is:

[0032]

[0033] As a preferred technical solution, the second step condensation reaction in step S2 is specifically as follows: 4,4-diaminobenzylbenzene-2,2-disulfonic acid is uniformly added to the first step condensation reaction system after the first step condensation reaction is completed, and the pH of the system is controlled to be 3.5-8 under the condition of the presence of an acid binding agent, and the temperature is raised to 20°C-50°C for the second step condensation reaction, and the disappearance of the amino value is taken as the reaction end point to obtain a second step condensation reaction system containing a second condensation product. By controlling the pH of the system to be 3.5-8 and carrying out the second step condensation reaction at a temperature of 20°C-50°C, the generation of a large amount of by-products due to excessively high temperature or pH is avoided, which seriously affects the quality and comprehensive performance of the product.

[0034] Preferably, the molar ratio of the 4,4-diaminobenzylbenzene-2,2-disulfonic acid to the condensation product is (0.8-1.2):1;

[0035] The structural formula of the dicondensation product is:

[0036]

[0037] As a preferred technical solution, the third step condensation reaction in step S3 is specifically as follows: diethanolamine is first added to the dicondensation reaction system after the second step condensation reaction is completed, and then an amino acid is added, an acid binding agent is used to adjust the system pH to 5.5-11, and the temperature is raised to 75°C to 120°C for the third step condensation reaction for 150-180 minutes to obtain a stable acid-resistant whitening agent mixture containing symmetrical and asymmetrical structures.

[0038] Preferably, the molar ratio of diethanolamine, amino acid and dicondensation product is (1-1.2):(1.15-1.3):2; preferably, the molar ratio of glycine to glutamic acid is 1:(1-1.5);

[0039] During the research process, the inventors found that by controlling the amino acids to a combination of glycine and glutamic acid in a molar ratio of 1:(1-1.5), and controlling the molar ratio of diethanolamine, amino acid, and dicondensation product to (1-1.2):(1.15-1.3):2, the third step condensation to obtain a stable acid-resistant whitening agent mixture containing symmetrical and asymmetrical structures can be fully and thoroughly reacted, and the obtained whitening agent has good solubility and stability.

[0040] As a preferred technical solution, the temperature of desalination and concentration in step S4 is 60-65° C. Preferably, the model of the nanofiltration membrane is NF8040HR.

[0041] Preferably, the nanofiltration desalination and concentration can be stopped when the mass concentration of chloride ions in the mixture in step S4 is lower than 0.8%.

[0042] In the prior art, the inorganic salts and organic hydrolyzed small molecules produced during the reaction of the whitening agent are removed by acid precipitation process to achieve the purpose of product purification, but the stability of the liquid fluorescent whitening agent cannot be effectively guaranteed. Most products will produce precipitation after less than three months, which seriously affects the use effect of the whitening agent. In addition, when the nanofiltration membrane is used for separation and purification in the prior art, the temperature needs to be controlled below 40°C to avoid excessive temperature causing changes in the internal structure of the nanofiltration membrane element and thus causing irreversible chronic damage. However, the membrane flux is small and the production efficiency is very low, which is not conducive to large-scale industrial production. During the exploration, the inventor It was found that based on the introduction of a mixture of glycine and glutamic acid in the third step condensation reaction, a specific NF8040HR nanofiltration membrane was used to desalt and concentrate the stable acid-resistant brightener mixture containing symmetrical and asymmetrical structures obtained in step S3, thereby achieving high-throughput desalination and concentration at 60-65°C without affecting the organic membrane elements, thereby improving production efficiency; in addition, by controlling the nanofiltration membrane desalination and concentration to a mass concentration of chloride ions in the mixture below 0.8%, the inorganic salt content and impurities in the brightener were reduced, the purity of the brightener was improved, and the storage stability of the product was ensured.

[0043] As a preferred technical solution, the raw materials for preparing the stable acid-resistant brightener include cyanuric chloride, 4,4'-diaminostilbene-2,2'-disulfonic acid, aniline, diethanolamine, and amino acid; the molar ratio of cyanuric chloride, 4,4'-diaminostilbene-2,2'-disulfonic acid, aniline, diethanolamine, and amino acid is (0.5-1.5): (0.3-1): (1-1.5): (0-1): (0-1);

[0044] As a preferred technical solution, the preparation method of the stable acid-resistant brightener comprises at least the following steps:

[0045] S1, adding cyanuric chloride to an ice-water mixture, cooling in an ice bath to keep the temperature below 0°C, and beating for 50-70 minutes; then adding 4,4-diaminobenzylbenzene-2,2-disulfonic acid and stirring for 50-70 minutes; adding an acid binding agent to adjust the system pH to 1.5-5, controlling the temperature to 0-30°C, and maintaining this pH for 100-120 minutes to obtain a contraction reaction system containing a contraction product;

[0046] S2, adding aniline dropwise at a uniform rate to the first condensation reaction system after the first condensation reaction is completed, controlling the system pH to 3.5-8 under the condition of the presence of an acid binding agent, raising the temperature to 20°C-50°C for the second condensation reaction, and taking the disappearance of the amino value as the reaction end point to obtain a second condensation reaction system containing a second condensation product;

[0047] S3, first add diethanolamine to the dicondensation reaction system after the second step condensation reaction is completed, and then add amino acids, use an acid binding agent to adjust the system pH to 5.5-11, raise the temperature to 75°C-120°C for the third step condensation reaction for 150-180min, and obtain a stable acid-resistant brightener mixture containing symmetrical and asymmetrical structures;

[0048] S4. Cooling the mixture obtained in S3 to 40-80° C., desalting and concentrating the mixture through a nanofiltration membrane until the mass concentration of chloride ions in the mixture is less than 0.8, thereby obtaining a stable acid-resistant brightener.

[0049] As a preferred technical solution, the raw materials for preparing the stable acid-resistant brightener include cyanuric chloride, aniline-2,5-bissulfonic acid monosodium salt, 4,4'-diaminostilbene-2,2'-disulfonic acid, diethylamine, and amino acid; the molar ratio of cyanuric chloride, aniline-2,5-bissulfonic acid monosodium salt, 4,4'-diaminostilbene-2,2'-disulfonic acid, diethylamine, and amino acid is (0.5-1.5): (1-1.5): (0.3-1): (0-1): (0-1);

[0050] As a preferred technical solution, the preparation method of the stable acid-resistant brightener comprises at least the following steps:

[0051] S1, adding cyanuric chloride to an ice-water mixture, cooling in an ice bath to keep the temperature below 0°C, and beating for 50-70 minutes; then adding aniline-2,5-bissulfonic acid monosodium salt and stirring for 50-70 minutes; adding an acid binding agent to adjust the system pH to 1.5-5, controlling the temperature to 0-30°C, and maintaining this pH for 100-120 minutes to obtain a contraction reaction system containing a contraction product;

[0052] S2, uniformly adding 4,4'-diaminostilbene-2,2'-disulfonic acid to the first condensation reaction system after the first condensation reaction is completed, controlling the system pH to 3.5-8 under the condition of the presence of an acid binding agent, raising the temperature to 20°C-50°C for the second condensation reaction, and taking the disappearance of the amino value as the reaction end point to obtain a dicondensation reaction system containing a dicondensation product;

[0053] S3, first add diethylamine to the dicondensation reaction system after the second step condensation reaction is completed, then add amino acid, use acid binding agent to adjust the system pH to 5.5-11, raise the temperature to 75°C-120°C for the third step condensation reaction for 150-180min, and obtain a stable acid-resistant brightener mixture containing symmetrical and asymmetrical structures;

[0054] S4. Cool the mixture obtained in S3 to 60-65° C., and desalt and concentrate the mixture through a nanofiltration membrane until the mass concentration of chloride ions in the mixture is less than 0.8 to obtain a stable acid-resistant brightener.

[0055] The third aspect of the present invention provides an application of a preparation process of a stable acid-resistant brightener, which is applied to the field of high-white paper production.

[0056] Beneficial Effects

[0057] 1. Aiming at the problem that the fluorescent brightener prepared in the prior art is not stable enough, so that amine substances are precipitated or stink, and the surface of the obtained paper is dark and the whiteness is not high during the application in papermaking, the present invention designs a preparation process of a stable acid-resistant brightener, which has simple process, low production cost, high product whiteness, good whitening effect, strong water solubility and anti-cation interference ability, meets the production and application requirements of high white paper, and has high market application value.

[0058] 2. Based on the system of the present invention, amino acids are added to carry out the third step condensation reaction by design, especially when the introduced amino acids are a mixture of glycine and glutamic acid in a molar ratio of (0-1): (0.1-1.2), a liquid fluorescent whitening agent containing an asymmetric structure is obtained after the reaction, which greatly improves the storage stability of the liquid fluorescent whitening agent. At the same time, the liquid fluorescent whitening agent with a symmetrical structure and the liquid fluorescent whitening agent with an asymmetric structure generated after the reaction have a composite whitening effect, and the optical behaviors of the liquid fluorescent whitening agents of different components do not interfere with each other, which greatly improves the whitening effect of the stable acid-resistant whitening agent, solves the problem that the surface of the obtained paper is dark and the whiteness is not high in the process of applying the fluorescent whitening agent to papermaking, and ensures the whiteness, water solubility and anti-cation interference ability of the product.

[0059] 3. In the present invention, by adopting specific preparation raw materials and controlling the molar ratio of each reaction raw material, on the one hand, each raw material is fully reacted during the reaction, avoiding the influence of raw material residue on the subsequent condensation reaction, reducing the generation of by-products, and ensuring product quality; on the other hand, a stable acid-resistant brightener containing symmetrical and asymmetrical structures is generated, thereby improving the whitening effect of the brightener.

[0060] 4. The present invention is designed to first add cyanuric chloride to an ice-water mixture, control the temperature to be below 0°C, add p-aminobenzenesulfonic acid to react after beating for 50-70 minutes, and use a NaOH solution or a Na2CO3 solution with a mass concentration of 15-20% as an acid binding agent. On the one hand, it is avoided that the by-products produced by the hydrolysis of cyanuric chloride affect its condensation reaction with p-aminobenzenesulfonic acid, resulting in reduced product purity and performance. On the other hand, p-aminobenzenesulfonic acid and cyanuric chloride in a molar ratio of (0.8-1.2):1 are uniformly and fully reacted to avoid the residual p-aminobenzenesulfonic acid affecting the second step condensation reaction, reduce the generation of by-products, and ensure the whitening performance of the product.

[0061] 5. The present invention, based on the introduction of a mixture of glycine and glutamic acid in the third step condensation reaction, uses a specific NF8040HR nanofiltration membrane to desalt and concentrate the stable acid-resistant brightener mixture containing symmetrical and asymmetrical structures obtained in step S3, thereby achieving high-flux desalination and concentration at 60-65° C. without affecting organic membrane elements, thereby improving production efficiency; in addition, by controlling the nanofiltration membrane to desalt and concentrate until the mass concentration of chloride ions in the mixture is lower than 0.8%, the inorganic salt content and impurities in the brightener are reduced, the purity of the brightener is improved, and the storage stability of the product is ensured. DETAILED DESCRIPTION

[0062] Example 1

[0063] Embodiment 1 of the present invention provides a stable acid-resistant brightener, wherein the raw materials for preparing the same include cyanuric chloride, p-aminobenzenesulfonic acid, 4,4'-diaminobenzene-2,2'-disulfonic acid, diethanolamine, and amino acid;

[0064] The amino acids are a combination of glutamic acid and glycine;

[0065] Embodiment 1 of the present invention provides a preparation process of a stable acid-resistant brightener, comprising the following steps:

[0066] (1) Add 250 g of water and 300 g of flake ice to a 2000 mL four-necked bottle, cool in an ice bath to keep the temperature below 0° C., add 30 g of cyanuric chloride and beat for 1 hour, add 28 g of p-aminobenzenesulfonic acid to the above solution, stir for 1 hour, adjust the pH to 3 with a 15% NaOH solution, maintain this pH for 2 hours, control the temperature at 20° C., until the pH is stable, and the first condensation reaction is completed;

[0067] (2) adding 29.2 g of 4,4-diaminobenzylbenzene 2,2-disulfonic acid to step (1) at a uniform rate, adjusting the pH to 4.8 with a 15% by mass NaOH solution, maintaining the pH at 4.8 for 2.5 hours, controlling the temperature at 35° C., and reacting until the amino value disappears, thereby completing the second step condensation reaction;

[0068] (3) First add 5.9 g of diethanolamine to step (2), then add 3.0 g of glycine and 5.9 g of glutamic acid, then heat to 100° C., adjust pH to 8 with 15% NaOH solution, and react for 3 hours;

[0069] (4) The feed liquid is cooled to 65°C and desalted and concentrated through a nanofiltration membrane. When the CI- concentration is less than 0.8, the nanofiltration is stopped to obtain a four-component stable acid-resistant whitening agent.

[0070] The stable acid-resistant whitening agent comprises component I, component II, component III and component IV;

[0071] Among them, the structure of component I is:

[0072]

[0073] The structure of component II is:

[0074]

[0075] The structure of component III is:

[0076]

[0077] The structure of component IV is:

[0078]

[0079] Example 2

[0080] Embodiment 2 of the present invention provides a stable acid-resistant brightener, wherein the raw materials for preparing the same include cyanuric chloride, 4,4'-diaminostilbene-2,2'-disulfonic acid, aniline, diethanolamine, and amino acid;

[0081] The amino acids are a combination of glutamic acid and glycine;

[0082] Embodiment 2 of the present invention provides a preparation process of a stable acid-resistant brightener, comprising the following steps:

[0083] (1) Add 250 g of water and 300 g of flake ice to a 2000 mL four-necked bottle, cool in an ice bath to keep the temperature below 0° C., add 30 g of cyanuric chloride and beat for 1 hour, add 30.4 g of 4,4-diaminobenzylbenzene 2,2-disulfonic acid to the above solution, stir for 1 hour, adjust the pH to 3 with a 15% NaOH solution, maintain this pH for 2 hours, and control the temperature at 20° C. until the pH is stable and the first condensation reaction is completed;

[0084] (2) 18.2 g of aniline was uniformly added dropwise to step (1), and the pH was adjusted to 4.8 with a 15% by mass NaOH solution. The pH was maintained at 35° C. for 2.5 hours, and the reaction was continued until the amino group disappeared. The second step condensation reaction was completed.

[0085] (3) First add 7.0 g of diethanolamine to step (2), then add 3.7 g of glycine and 7.0 g of glutamic acid, then heat to 100° C., adjust pH to 8 with 15% NaOH solution, and react for 3 hours;

[0086] (4) The feed liquid is cooled to 65°C and desalted and concentrated through a nanofiltration membrane. When the CI- concentration is less than 0.8, the nanofiltration is stopped to obtain a four-component stable acid-resistant whitening agent.

[0087] The stable acid-resistant whitening agent comprises component I, component II, component III and component IV;

[0088] Among them, the structure of component I is:

[0089]

[0090] The structure of component II is:

[0091]

[0092] The structure of component III is:

[0093]

[0094] The structure of component IV is:

[0095]

[0096] Example 3

[0097] Embodiment 3 of the present invention provides a stable acid-resistant brightener, wherein the raw materials for preparing the same include cyanuric chloride, aniline-2,5-bissulfonic acid monosodium salt, 4,4'-diaminobenzene-2,2'-disulfonic acid, diethylamine, and amino acid;

[0098] The amino acids are a combination of glutamic acid and glycine;

[0099] Embodiment 3 of the present invention provides a preparation process of a stable acid-resistant brightener, comprising the following steps:

[0100] (1) Add 250 g of water and 300 g of flake ice to a 2000 mL four-necked bottle, cool in an ice bath to keep the temperature below 0° C., add 30 g of cyanuric chloride and beat for 1 hour, add 44.9 g of p-aniline-2,5-bissulfonic acid monosodium salt to the above solution, stir for 1 hour, adjust the pH to 3 with a 15% mass fraction NaOH solution, maintain this pH for 2 hours, control the temperature at 20° C., until the pH is stable, and the first condensation reaction is completed;

[0101] (2) adding 35.7 g of 4,4'-diaminostilbene-2,2'-disulfonic acid to step (1) at a uniform rate, adjusting the pH to 4.8 with a 15% by mass NaOH solution, maintaining the pH at 4.8 for 2.5 hours, controlling the temperature at 35°C, and reacting until the amino value disappears, thereby completing the second step condensation reaction;

[0102] (3) First add 7.2 g of diethylamine to step (2), then add 6.5 g of glycine and 1.5 g of glutamic acid, then heat to 100° C., adjust pH to 8 with 15% NaOH solution, and react for 3 hours;

[0103] (4) The feed liquid is cooled to 65°C and desalted and concentrated through a nanofiltration membrane. When the CI- concentration is less than 0.8, the nanofiltration is stopped to obtain a four-component stable acid-resistant whitening agent.

[0104] The stable acid-resistant whitening agent comprises component I, component II, component III and component IV;

[0105] Among them, the structure of component I is:

[0106]

[0107] The structure of component II is:

[0108]

[0109] The structure of component III is:

[0110]

[0111] The structure of component IV is:

[0112]

[0113] Example 4

[0114] The embodiment of the present invention provides a stable acid-resistant brightener, and the specific implementation method is the same as that of Example 1, except that a soda ash solution with a mass fraction of 20% is used as an acid binding agent to adjust the pH of each step.

[0115] Performance Testing Methods

[0116] 1. Enhance whiteness: Weigh 0.5g of Examples 1-4 respectively, and dilute to 500mL of sample solution with water. Dye bath preparation: 50mL of sample solution and 10mL of 10% sodium sulfate solution, add water to 200mL. After the dye bath is prepared, place the dye vat in a water bath for dyeing, weigh 5g of cotton cloth and dye at room temperature, and keep turning it over, raise the temperature to 50℃ within 30min, continue dyeing at this temperature for 30min, take out after dyeing, wash with water and dry. Under this condition, measure the whiteness value of the standard sample and the test sample respectively.

[0117] Whitening intensity = W1 (whiteness value of sample) / W2 (whiteness value of standard sample). See Table 1 for performance test results.

[0118] 2. Low temperature stability: The brightener prepared in Example 1-4 is placed at 4°C for 24 hours. If no precipitation is observed after 24 hours, the low temperature stability of the brightener is recorded as "qualified".

[0119] Table 1

[0120]

[0121]

Claims

1. A stable acid-resistant brightener, characterized in that: The raw materials for its preparation include cyanuric chloride, p-aminobenzenesulfonic acid, 4,4'-diaminobenzene-2,2'-disulfonic acid, diethanolamine, and amino acid; The amino acids are a combination of glutamic acid and glycine; The preparation process of the stable acid-resistant brightener comprises the following steps: (1) Add 250 g of water and 300 g of flake ice to a 2000 mL four-necked bottle, cool in an ice bath to keep the temperature below 0° C., add 30 g of cyanuric chloride and beat for 1 hour, add 28 g of p-aminobenzenesulfonic acid to the above solution, stir for 1 hour, adjust the pH to 3 with a 15% NaOH solution, maintain this pH for 2 hours, control the temperature at 20° C., until the pH is stable, and the first condensation reaction is completed; (2) adding 29.2 g of 4,4-diaminostilbene 2,2-disulfonic acid to step (1) at a uniform rate, adjusting the pH to 4.8 with a 15% by mass NaOH solution, maintaining the pH at 4.8 for 2.5 hours, controlling the temperature at 35° C., and reacting until the amino value disappears, thereby completing the second step condensation reaction; (3) First add 5.9 g of diethanolamine to step (2), then add 3.0 g of glycine and 5.9 g of glutamic acid, then heat to 100° C., adjust pH to 8 with 15% NaOH solution, and react for 3 hours; (4) cooling the feed liquid to 65° C., desalting and concentrating the feed liquid through a nanofiltration membrane, and stopping the nanofiltration when the CI- concentration is less than 0.8 to obtain a four-component stable acid-resistant brightener; The stable acid-resistant whitening agent comprises component I, component II, component III and component IV; Among them, the structure of component I is: The structure of component II is: The structure of component III is: The structure of component IV is:

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