A fluorescent whitening composition, its preparation method and application

Abstract

The present invention relates to the field of fluorescent whitening, and discloses a fluorescent whitening composition, a preparation method and an application thereof. The fluorescent whitening composition comprises the following components in parts by weight: 30-45 parts of acrylate emulsion, 5-12 parts of fluorescent whitening agent, 1-5 parts of modified additive, and 10-25 parts of deionized water; the fluorescent whitening agent is an amino-functionalized nano-titanium dioxide grafted and modified fluorescent matrix, and the modified fluorescent matrix is prepared by carrying out a first-step nucleophilic substitution reaction between cyanuric chloride and p-aminobenzenesulfonic acid and then carrying out a second-step nucleophilic substitution reaction with the fluorescent matrix 4,4'-diaminostilbene-2,2'-disulfonic acid; the modified additive is prepared by covalently grafting and coating graphene oxide on the surface of nano-silica and grafting glycidyl versatate. By adding the fluorescent whitening agent and the modified additive, the present invention can improve the whiteness of paper, has an obvious effect of inhibiting paper yellowing, and can effectively improve the tensile strength, tearing degree, water resistance and aging resistance of paper.

Description

Technical Field

[0001] The present invention belongs to the technical field of fluorescent whitening, and particularly relates to a fluorescent whitening composition, a preparation method thereof, and an application thereof. Background Art

[0002] A fluorescent whitening agent is an organic compound that can absorb ultraviolet light and emit blue or blue-violet fluorescence. For a substance adsorbed with a fluorescent whitening agent, on the one hand, it can reflect the visible light irradiated on the object, and at the same time, it can convert the absorbed invisible ultraviolet light (wavelength 300 - 400 nm) into blue or blue-violet visible light and emit it. Since blue and yellow are complementary colors, the yellow in the article matrix is eliminated, making it appear white and bright; on the other hand, it increases the light emission rate of the object, and the intensity of the emitted light exceeds the intensity of the original visible light projected onto the object being treated. Therefore, when people look with their eyes, the whiteness of the object increases, thus achieving the purpose of whitening.

[0003] The popularization of high-yield pulp is of great significance for alleviating problems such as the shortage of wood pulp resources and environmental pollution that the pulp and paper industry has long faced. High-yield pulp not only has a high pulping yield (up to 80% - 95%), low pollution, but also has a higher bulk and opacity of the formed paper, and has a broad application prospect in the pulp and paper industry. However, high-yield pulp has a high lignin content and is prone to photoinduced yellowing, which limits its application in high-quality paper products. The use of fluorescent whitening agents can effectively alleviate this problem. Among them, stilbene-type fluorescent whitening agents are the most widely used fluorescent whitening agents in the paper-making industry, having advantages such as significant whitening effect, good ultraviolet absorption performance, and high fluorescence quantum yield. However, they also have disadvantages such as poor water solubility, serious photoinduced yellowing phenomenon, easy loss during coating, and poor binding ability with fibers. The heat resistance aging and ultraviolet aging resistance of the paper after its application for paper coating need to be further improved. Summary of the Invention

[0004] To solve the deficiencies mentioned in the above background art, the purpose of the present invention is to provide a fluorescent whitening composition, a preparation method thereof, and an application thereof. By adding a fluorescent whitening agent and a modified additive, the whiteness of the paper can be increased, the effect of inhibiting paper yellowing is obvious, and it can effectively improve the tensile strength, tearing degree, water resistance, and aging resistance of the paper.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A fluorescent whitening composition, comprising the following components in parts by weight: 30 - 45 parts of acrylate emulsion, 5 - 12 parts of fluorescent whitening agent, 1 - 5 parts of modified additive, and 10 - 25 parts of deionized water;

[0007] The fluorescent brightener is an amino-functionalized nano-titanium dioxide grafted and modified fluorescent matrix. The modified fluorescent matrix is prepared by performing a first-step nucleophilic substitution reaction of cyanuric chloride with sulfanilic acid and then a second-step nucleophilic substitution reaction with the fluorescent matrix 4,4-diaminostilbene-2,2-disulfonic acid. The structural formula of the modified fluorescent matrix is as follows:

[0008]

[0009] The modified additive is prepared by covalently grafting and coating graphene oxide on the surface of nano-silica and grafting glycidyl versatate.

[0010] Preferably, the preparation method of the fluorescent brightener comprises the following steps:

[0011] A. Take cyanuric chloride and deionized water in a reactor, place it in an ice-water bath and stir evenly. Dissolve sulfanilic acid in deionized water and add it to the reactor. Adjust the pH value of the system to 6, control the reaction temperature at 0-5°C, and react for 2-3 h to obtain a primary product;

[0012] B. Dissolve 4,4-diaminostilbene-2,2-disulfonic acid and anhydrous potassium carbonate in deionized water, adjust the pH value of the system to 7-8 to obtain a mixed solution. Add the mixed solution to the primary product, continue to adjust the pH value of the system to 7-8, and then react at 45-60°C for 2-4 h to obtain a modified fluorescent matrix;

[0013] C. Ultrasonically disperse nano-titanium dioxide in a mixed solution of ethanol and deionized water, add glacial acetic acid dropwise to adjust the pH value of the system to 4-5, raise the temperature to 70-85°C, slowly add 3-aminopropyltriethoxysilane dropwise, and react for 6-8 h after the addition is completed. After the reaction is completed, centrifuge, wash, and dry to obtain amino-functionalized nano-titanium dioxide;

[0014] D. Add amino-functionalized nano-titanium dioxide to the modified fluorescent matrix, raise the temperature to 80-95°C, adjust the pH value of the system to 9-10, react for 2-4 h, and then perform suction filtration, washing, and drying to obtain the fluorescent brightener.

[0015] Preferably, the molar ratio of cyanuric chloride, sulfanilic acid, 4,4-diaminostilbene-2,2-disulfonic acid, anhydrous potassium carbonate, and amino-functionalized nano-titanium dioxide is 1:1.05-1.5:0.5-0.8:0.5-0.8:0.6-1.

[0016] Preferably, the preparation method of the modified additive comprises the following steps:

[0017] (1) Take nano-silica and ultrasonically disperse it in absolute ethanol. Add γ-glycidoxypropyltrimethoxysilane and reflux under nitrogen for 2 - 4 h. After the reaction is completed, cool it to room temperature, wash and dry it to prepare modified nano-silica;

[0018] (2) Take graphene oxide and ultrasonically disperse it in deionized water to obtain a dispersion. Take lysine and dissolve it in deionized water, adjust the pH value of the system to 7 - 8 to obtain a mixed solution. Mix the dispersion and the mixed solution and ultrasonically disperse them, and react at 25 - 40 °C for 18 - 24 h. After the reaction is completed, wash and dry it to prepare modified graphene oxide;

[0019] (3) Take modified graphene oxide and modified nano-silica in a reactor, add deionized water and ultrasonically disperse it, then react at 40 - 50 °C for 16 - 24 h. After the reaction is completed, wash and dry it to prepare a composite additive;

[0020] (4) Take the composite additive and dissolve it in butyl acetate and ultrasonically disperse it. Add triphenylphosphine, heat up to 90 - 120 °C, then add glycidyl versatate and react for 8 - 12 h. After the reaction is completed, filter, wash and dry it to prepare a modified additive.

[0021] Preferably, in the step (2), the mass ratio of graphene oxide to lysine is 1:3 - 5.

[0022] Preferably, in the step (3), the mass ratio of modified graphene oxide to modified nano-silica is 2 - 3:1.

[0023] Preferably, in the step (4), the mass ratio of the composite additive to glycidyl versatate is 1:4 - 8.

[0024] The preparation method of the fluorescent whitening composition as described above includes the following steps: Stir and mix acrylate emulsion, fluorescent whitening agent, modified additive and deionized water, with a stirring speed of 60 - 120 rpm and a time of 0.5 - 1 h. After the stirring is completed, the fluorescent whitening composition is obtained.

[0025] An application of the fluorescent whitening composition as described above in paper, and the fluorescent whitening composition is used for surface coating of paper.

[0026] The beneficial effects of the present invention:

[0027] The present invention uses cyanuric chloride and sulfanilic acid as raw materials, 4,4-diaminostilbene-2,2-disulfonic acid as the fluorescent matrix, and then connects the aminated nano-titanium dioxide with the modified fluorescent matrix through nucleophilic substitution to prepare a fluorescent brightener. The introduction of multiple sulfonic acid groups can increase the water solubility of the fluorescent brightener and improve the binding strength between the fluorescent brightener and the paper fiber. The nano-titanium dioxide latex particles contained in the fluorescent brightener are evenly adsorbed on the paper surface, effectively filling the fiber gaps, making the binding between fibers closer, effectively improving the mechanical properties of the paper, reducing the water absorption capacity of single fibers at the same time, and improving the water resistance of the paper. In addition, nano-titanium dioxide has high whiteness and strong coloring power, and can play a role in physical whitening after being coated on the paper surface, significantly improving the whiteness of the paper. Moreover, nano-titanium dioxide has antibacterial, deodorant, and mildew-proof effects, and the introduction of nano-titanium dioxide particles can enable the fluorescent brightener to play a role in shielding ultraviolet rays while exerting an optical whitening effect, effectively inhibiting the yellowing of the paper caused by ultraviolet light irradiation.

[0028] The present invention uses γ-glycidoxypropyltrimethoxysilane to modify nano-silica particles to make their surfaces carry epoxy groups, and then uses lysine with a diamine structure as a bridge to covalently graft and coat graphene oxide on the surface of nano-silica to prepare a composite additive. It can not only increase the layer spacing of graphene oxide, facilitate the dispersion of graphene oxide, but also increase the contact area between graphene oxide and the matrix, improve the compatibility between the composite additive and the matrix. The addition of the composite additive can endow the paper with excellent mechanical properties and heat insulation properties. In addition, the carboxyl group on the surface of the composite additive reacts with the epoxy group on the surface of glycidyl versatate, thereby introducing a tertiary carbon hydrophobic group on the surface of the composite additive to improve the water resistance of the paper. At the same time, the added acrylate emulsion has the function of bonding and film-forming, can adjust the tensile strength of the paper, enhance the bearing capacity of the paper, and prevent it from cracking due to uneven tension during use. The fluorescent brightening composition prepared by the present invention can improve the whiteness of the paper, has an obvious effect of inhibiting paper yellowing, and can effectively improve the tensile strength, tearing degree, water resistance and aging resistance of the paper. Detailed implementation manners

[0029] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0030] Example 1 A preparation method of a fluorescent brightener includes the following steps:

[0031] A. Take 5.9 g of cyanuric chloride and 20 mL of deionized water in a reactor, place it in an ice-water bath and stir evenly. Dissolve 6.2 g of sulfanilic acid in deionized water and add it to the reactor. Adjust the pH value of the system to 6, control the reaction temperature at 4 °C, and react for 3 h to obtain a primary product.

[0032] B. Take 6.6 g of 4,4'-diaminostilbene-2,2'-disulfonic acid and 6.2 g of anhydrous potassium carbonate and dissolve them in deionized water. Adjust the pH value of the system to 7 to obtain a mixed solution. Add the mixed solution to the primary product, continue to adjust the pH value of the system to 7, and then place it at 45 - 60 °C and react for 2 - 4 h to obtain a modified fluorescent matrix.

[0033] C. Take 4 g of nano-titanium dioxide and ultrasonically disperse it in a mixed solution of 80 mL of ethanol and 20 mL of deionized water. Dropwise add glacial acetic acid to adjust the pH value of the system to 5, heat up to 80 °C, and slowly dropwise add 5.2 g of 3-aminopropyltriethoxysilane. After the dropping is completed, react for 7 h. After the reaction is completed, centrifuge, wash, and dry to obtain amino-functionalized nano-titanium dioxide.

[0034] D. Add 7.8 g of amino-functionalized nano-titanium dioxide to the modified fluorescent matrix, heat up to 95 °C, adjust the pH value of the system to 9, react for 4 h, and then filter, wash, and dry to obtain a fluorescent brightener.

[0035] Example 2 A preparation method of a modified additive includes the following steps:

[0036] (1) Take 1 g of nano-silica and ultrasonically disperse it in 50 mL of absolute ethanol. Add 1.4 g of γ-glycidoxypropyltrimethoxysilane, reflux and react under nitrogen for 2 h. After the reaction is completed, cool to room temperature, wash, and dry to prepare modified nano-silica.

[0037] (2) Take 0.8 g of graphene oxide and ultrasonically disperse it in 150 mL of deionized water to obtain a dispersion. Take 3.2 g of lysine and dissolve it in deionized water, add 1 mL of 4.2 mg / mL sodium hydroxide solution to obtain a mixed solution. Mix the dispersion and the mixed solution and ultrasonically disperse them, place at 30 °C and react for 24 h. After the reaction is completed, wash and dry to prepare modified graphene oxide.

[0038] (3) Take 1 g of modified graphene oxide and 0.5 g of modified nano-silica in a reactor, add 100 mL of deionized water and ultrasonically disperse, and then place at 45 °C and react for 18 h. After the reaction is completed, wash and dry to prepare a composite additive.

[0039] (4) Dissolve 1 g of the composite additive in 40 mL of butyl acetate and disperse it by ultrasonic treatment. Add 0.004 g of triphenylphosphine, heat up to 100 °C, and then add 4.7 g of glycidyl versatate and react for 12 h. After the reaction is completed, filter by suction, wash, and dry to prepare the modified additive.

[0040] Example 3 A fluorescent whitening composition, comprising the following components in parts by weight: 32 parts of acrylate emulsion, 5 parts of the fluorescent whitening agent prepared in Example 1, 1 part of the modified additive prepared in Example 2, and 10 parts of deionized water.

[0041] The preparation method of the above fluorescent whitening composition comprises the following steps: Stir and mix the acrylate emulsion, fluorescent whitening agent, modified additive, and deionized water at a stirring speed of 80 rpm for 40 min, and after the stirring is completed, the fluorescent whitening composition is obtained.

[0042] Example 4 A fluorescent whitening composition, comprising the following components in parts by weight: 40 parts of acrylate emulsion, 8 parts of the fluorescent whitening agent prepared in Example 1, 3 parts of the modified additive prepared in Example 2, and 18 parts of deionized water.

[0043] The preparation method of the above fluorescent whitening composition is the same as that of Example 3.

[0044] Example 5 A fluorescent whitening composition, comprising the following components in parts by weight: 44 parts of acrylate emulsion, 12 parts of the fluorescent whitening agent prepared in Example 1, 5 parts of the modified additive prepared in Example 2, and 23 parts of deionized water.

[0045] The preparation method of the above fluorescent whitening composition is the same as that of Example 3.

[0046] Comparative Example 1 A fluorescent whitening composition, comprising the following components in parts by weight: 32 parts of acrylate emulsion, 5 parts of commercially available fluorescent whitening agent VBL, 1 part of the modified additive prepared in Example 2, and 10 parts of deionized water.

[0047] The preparation method of the above fluorescent whitening composition is the same as that of Example 3.

[0048] Comparative Example 2 A fluorescent whitening composition, comprising the following components in parts by weight: 32 parts of acrylate emulsion, 5 parts of the fluorescent whitening agent prepared in Example 1, and 10 parts of deionized water.

[0049] The preparation method of the above fluorescent whitening composition is the same as that of Example 3.

[0050] Performance testing

[0051] Make the poplar APMP on a paper making machine with a basis weight of 100 g / m 2For the circular paper, the fluorescent whitening compositions prepared in Examples 3-5 and Comparative Examples 1-2 were respectively coated on the paper surface, and the coating amount was 2 g / m 2 , and then performance tests were carried out:

[0052] (1) Mechanical property test: The tensile strength and tear strength of the coated paper were detected by a tensile strength tester and a tear strength tester, and the data results are shown in Table 1.

[0053] (2) Whiteness and yellowing return value test: After the paper sample was air-dried, it was placed in an ultraviolet aging chamber for ultraviolet aging test. The output power of the ultraviolet aging chamber was 5.3 mW / cm 2 , the temperature was set at 25 °C, the wavelength of the ultraviolet lamp tube was 340 nm, the paper sample was laid flat in the chamber, irradiated for 38 h, the whiteness was measured by a colorimeter, and the yellowing return value (PC value) was calculated. The data results are shown in Table 1.

[0054] (3) Ultraviolet light aging test: The paper sample was put into an ultraviolet aging chamber, the height of the light source was adjusted so that the paper sample was about 10 cm away from the light source, the light source was 254 nm ultraviolet light, and the irradiation time was 72 h. The data results are shown in Table 1.

[0055] (4) Dry heat aging test: Referring to GB / T 464-2008, the paper sample was put into a constant temperature drying oven, the aging temperature was 105 °C, and the aging time was 72 h. The data results are shown in Table 1.

[0056] (5) Water resistance test: The contact angle of the water droplet on the paper surface for 6 s was measured by a contact angle tester. The data results are shown in Table 1.

[0057] Table 1 Test results of sample performance

[0058]

[0059] It can be seen from the data in Table 1 that the fluorescent whitening compositions prepared in Examples 3-5 and Comparative Examples 1-2 of the present invention can endow the paper with excellent tensile strength and tear strength, and at the same time can significantly improve the whiteness of the paper, and have an obvious effect on inhibiting the yellowing of the paper. Its water contact angle increases, improving the water resistance and waterproofness of the paper.

[0060] In the description of this specification, the description referring to terms such as "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0061] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification is only to illustrate the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed.

Claims

1. A fluorescent whitening composition, characterized in that: The invention comprises the following components in parts by weight: 30-45 parts of acrylic emulsion, 5-12 parts of fluorescent brightener, 1-5 parts of modified additive, and 10-25 parts of deionized water; The fluorescent brightener is an amination-modified fluorescent matrix grafted with nano-titanium dioxide. The modified fluorescent matrix is ​​prepared by a first step nucleophilic substitution reaction between cyanuric chloride and p-aminobenzenesulfonic acid and a second step nucleophilic substitution reaction with the fluorescent matrix 4,4'-diaminostilbene-2,2'-disulfonic acid. The structural formula of the modified fluorescent matrix is ​​as follows: ； The modified additive is prepared by covalently grafting graphene oxide onto the surface of nano silicon dioxide and grafting tert-butyl glycidyl carbonate.

2. The fluorescent whitening composition according to claim 1, characterized in that The preparation method of the fluorescent whitening agent comprises the following steps: A. Take cyanuric chloride and deionized water in a reactor, place them in an ice water bath and stir them evenly, dissolve p-aminobenzenesulfonic acid in deionized water and add them to the reactor, adjust the pH value of the system to 6, control the reaction temperature to 0-5°C, react for 2-3h, and obtain the initial product; B. Dissolve 4,4'-diaminostilbene-2,2'-disulfonic acid and anhydrous potassium carbonate in deionized water, adjust the pH value of the system to 7-8 to obtain a mixed solution, add the mixed solution to the initial product, continue to adjust the pH value of the system to 7-8, and then place it at 45-60°C for 2-4 hours to obtain a modified fluorescent matrix; C. Ultrasonic dispersion of nano-titanium dioxide in a mixture of ethanol and deionized water, dropwise addition of glacial acetic acid to adjust the pH value of the system to 4-5, raise the temperature to 70-85°C, slowly dropwise addition of 3-aminopropyltriethoxysilane, react for 6-8 hours after the addition is completed, and after the reaction is completed, centrifugation, washing, and drying are performed to obtain amino-modified nano-titanium dioxide; D. Add amino nano-titanium dioxide to the modified fluorescent matrix, raise the temperature to 80-95°C, adjust the pH value of the system to 9-10, react for 2-4 hours, filter, wash and dry to obtain a fluorescent whitening agent.

3. The fluorescent whitening composition according to claim 2, characterized in that The molar ratio of cyanuric chloride, p-aminobenzenesulfonic acid, 4,4'-diaminobenzene-2,2'-disulfonic acid, anhydrous potassium carbonate and amino nano-titanium dioxide is 1:1.05-1.5:0.5-0.8:0.5-0.8:0.6-1.

4. The fluorescent whitening composition according to claim 1, characterized in that The preparation method of the modified additive comprises the following steps: (1) Nano-silica was ultrasonically dispersed in anhydrous ethanol, γ-glycidyloxypropyltrimethoxysilane was added, nitrogen was passed through the reflux reaction for 2-4 hours, and after the reaction was completed, it was cooled to room temperature, washed and dried to prepare modified nano-silica; (2) ultrasonically dispersing graphene oxide in deionized water to obtain a dispersion, dissolving lysine in deionized water, adjusting the pH value of the system to 7-8 to obtain a mixed solution, mixing the dispersion with the mixed solution and ultrasonically dispersing the mixture, reacting at 25-40° C. for 18-24 h, and washing and drying after the reaction to obtain modified graphene oxide; (3) taking modified graphene oxide and modified nano-silica into a reactor, adding deionized water for ultrasonic dispersion, and then reacting at 40-50°C for 16-24h. After the reaction is completed, washing and drying are performed to prepare a composite additive; (4) The composite additive is dissolved in butyl acetate and dispersed by ultrasonication, triphenylphosphine is added, the temperature is raised to 90-120°C, and then tert-butyl glycidyl carbonate is added to react for 8-12 hours. After the reaction is completed, the modified additive is prepared by filtration, washing and drying.

5. The fluorescent whitening composition according to claim 4, characterized in that: In the step (3), the mass ratio of modified graphene oxide to modified nano-silicon dioxide is 2-3:

1.

6. The fluorescent whitening composition according to claim 4, characterized in that: In the step (4), the mass ratio of the composite additive to tert-butyl glycidyl carbonate is 1:4-8.

7. The method for preparing the fluorescent whitening composition according to claim 1, characterized in that: The method comprises the following steps: mixing acrylate emulsion, fluorescent whitening agent, modification additive and deionized water by stirring, the stirring speed is 60-120 rpm, the time is 0.5-1 hour, and the fluorescent whitening composition is obtained after the stirring is completed.

8. Use of the fluorescent whitening composition according to claim 1 in paper, characterized in that: The fluorescent whitening composition is used for coating the surface of paper.

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