Synthesis method of plant extract cardanol modified benzotriazole ultraviolet absorbent

Abstract

The invention relates to the technical field of ultraviolet absorbents, in particular to a synthetic method of a plant extract cardanol modified benzotriazole ultraviolet absorbent, which comprises the following steps: S1, diazotization reaction, S2, cardanol modification, S3, coupling reaction, S4, reduction reaction, and S5, synthesis of a target product. The synthesis method of the benzotriazole ultraviolet absorbent, provided by the invention, has the advantages of simple reaction conditions, green production and relatively strong weather resistance of the product.

Description

Technical Field

[0001] The present application relates to the technical field of ultraviolet absorbers, and in particular to a method for synthesizing a benzotriazole ultraviolet absorber modified with plant extract cardanol. Background Art

[0002] Ultraviolet light absorbers are a type of light stabilizer that can absorb the ultraviolet light in sunlight and fluorescent light sources without changing themselves. Under sunlight and fluorescence, polymer materials undergo auto-oxidation reactions due to the action of ultraviolet light, which leads to the degradation of polymers and deterioration of appearance and mechanical properties. After adding ultraviolet light absorbers, ultraviolet light can be selectively absorbed, turning it into harmless energy that is released or consumed. Ultraviolet light absorbers can be divided into benzophenones, salicylates, triazines, benzotriazoles (also known as benzotriazoles) and substituted acrylonitriles according to their structures. Ultraviolet light absorbers have been widely used in various products, including plastics, coatings, textiles and care products, and in the development of UV-resistant fibers and clothing.

[0003] The Chinese invention patent with publication number CN113480488A discloses a liquid or low melting point benzotriazole ultraviolet absorber and a preparation method thereof. Using cardanol (or hydrogenated cardanol) as a raw material, a liquid or low melting point benzotriazole ultraviolet absorber is obtained according to a conventional preparation method.

[0004] This technical solution uses cashew nut monophenol as a raw material when producing benzotriazole ultraviolet absorbers. Since there is only one hydroxyl group on the benzene ring of cashew nut monophenol, the positioning effect is poor, resulting in more ultraviolet absorbers produced as by-products, and lower purity and yield. At the same time, the ultraviolet absorbers produced by this technical solution have poor weather resistance and tend to turn yellow when exposed to sunlight for a long time, affecting their appearance. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for synthesizing a benzotriazole ultraviolet absorber with simple reaction conditions, green production and strong weather resistance of the product.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions: A method for synthesizing a benzotriazole ultraviolet absorber modified by plant extract cardanol comprises the following steps: S1: Diazotization reaction: Add substituted or unsubstituted o-nitroaniline and dilute hydrochloric acid to the reactor, mix well, slowly add sodium nitrite solution dropwise under low temperature, and continue stirring to react to obtain diazo compound A. S2: Cardanol modification: Cardanol was mixed with 20% nitric acid, and stirred continuously under heating conditions for reaction, and then steam distilled to obtain the intermediate product nitrocardanol. S3: Coupling reaction: Add nitrocardanol and organic solvent to the reactor, add alkaline catalyst after complete dissolution, slowly drop diazo liquid A under low temperature stirring condition, and react to obtain intermediate product B. S4: Reduction reaction: Add intermediate product B and anhydrous ethanol to the reactor, stir evenly, add metal catalyst, slowly drop concentrated hydrochloric acid under stirring and heating conditions, and react to obtain intermediate product C. S5: Synthesis of target product: Add intermediate product C, sodium nitrite, nitrous acid and dilute hydrochloric acid into the reactor, continue to stir the reaction, add a reducing agent after the reaction is completed and heat to obtain the target product, cardanol-modified benzotriazole ultraviolet absorber.

[0007] By adopting the above technical scheme, the main purpose of this technical scheme is to use the long carbon chain on the benzene ring of cardanol to replace the alkoxy group on the benzene ring of the traditional benzotriazole ultraviolet absorber, so as to achieve the effect of modification and green production.

[0008] Traditional benzotriazole absorbers are generally prepared by reacting o-nitroaniline with phenol and then reacting alkyl sodium with hydroxyl to generate benzotriazole ultraviolet absorbers. In the two steps of reacting o-nitroaniline with phenol and reacting alkyl sodium with the intermediate product to generate the target product, the reaction end point is difficult to control, and more by-products are easily generated, resulting in low purity and yield of the final product and high production cost. The cardanol used in the present technical solution is a type of natural phenolic compound from cereals or plants extracted from cashew nut shell liquid (CNSL). As a natural plant extract, the material cost is lower than that of the traditional production method. When reacting cardanol with a diazo compound A, in order to increase the selectivity of the reaction position and reduce the generation of by-products, the present technical solution uses a diazotization reaction to first replace a nitro group on the benzene ring of cardanol, and then react the intermediate product with a diazo compound A, thereby improving the selectivity of the reaction and greatly increasing the yield of the ortho-substituted product of cardanol, thereby improving the purity and yield of the reaction product and reducing the production cost.

[0009] Benzotriazole ultraviolet absorbers are often added to plastics, coatings, cosmetics and other products. However, due to the presence of alkoxy groups in benzotriazole ultraviolet absorbers, such ultraviolet absorbers not only have obvious photodegradation effects and poor weather resistance, but are also prone to yellowing and reduced ultraviolet absorption capacity under long-term exposure to light sources. At the same time, due to the presence of alkoxy groups, the dispersion effect in resin and rubber materials is poor, which makes the use scope of such ultraviolet absorbers small. The technical solution uses cardanol as a raw material, so that the original alkoxy group is replaced by the long carbon chain of cardanol in the final product, and the carbon chain is more stable, so that the benzotriazole ultraviolet absorber produced by the technical solution has stronger weather resistance and can still maintain whiteness under long-term light exposure. At the same time, the presence of the long carbon chain makes the benzotriazole ultraviolet absorber produced by the technical solution easier to disperse in polyester materials, thereby expanding the scope of use.

[0010] In the present invention, the substituted or unsubstituted o-nitroaniline in step S1 includes one or a combination of o-nitroaniline, chloro-o-nitroaniline and bromo-o-nitroaniline.

[0011] Through the above technical scheme, when there is a substituent on o-nitroaniline, the ultraviolet absorber finally produced has good weather resistance.

[0012] In the present invention, the substituted or unsubstituted o-nitroaniline in step S1 is chloro-o-nitroaniline.

[0013] Through the above technical solution, operators have found through experiments that when the substituent on o-nitroaniline is chlorine, the ultimately produced ultraviolet absorber has higher stability in resin and rubber materials.

[0014] In the present invention, the cardanol in step S2 includes one or more combinations of cardanol and cardanol diphenol, and the structure of the cardanol is as follows: (R=-C 15 H 31-2n , where n = 0 to 3) The structure of the cashew nut diphenol is shown below: (R=C 15 ~C 17 , containing 1-3 double bonds).

[0015] Through the above technical scheme, cardanol, as a type of natural phenolic compound from cereals or plants extracted from cashew nut shell liquid (CNSL), conforms to the current general direction of green production. Since cardanol contains a variety of biophenols, this technical scheme uses cashew monophenol and cashew diphenol, so that in the final product, the long carbon chain on cardanol or cashew diphenol replaces the methoxy group on the benzene ring of the traditional benzotriazole ultraviolet absorber, so that the ultraviolet absorber produced by this technical scheme has better weather resistance. At the same time, due to the position of the substituents on the benzene ring of cardanol and cashew diphenol, they have better selectivity when undergoing substitution reaction with diazo compound A, thereby improving the purity of the final product.

[0016] In the present invention, the cardanol in step S2 is cardanol.

[0017] Through the above technical solution, since cashew diphenol has two hydroxyl groups on the benzene ring, when it reacts with substituted or unsubstituted o-nitroaniline, the positioning effect is more obvious and the by-product content is lower.

[0018] In the present invention, the metal catalyst in step S3 is one or a combination of active iron powder and active zinc powder.

[0019] According to the above technical solution, when performing the reduction reaction, it is necessary to add relatively active metal powder as a catalyst to increase the reaction rate. Active iron powder and active zinc powder are relatively active and have a good catalytic effect in this technical solution.

[0020] In the present invention, the reaction temperature in steps S1 and S3 is 0-5°C.

[0021] According to the above technical solution, since hydrochloric acid, nitrous acid and sodium nitrite are easily heated to produce harmful gases, the reaction temperature needs to be maintained in a relatively low range in this technical solution to reduce the decomposition of nitrous acid and sodium nitrite and the volatilization of hydrochloric acid.

[0022] In the present invention, the reducing agent in step S5 is one or a combination of phosphorous acid and hypophosphorous acid.

[0023] Through the above technical solution, when removing the amino group on the benzene ring, adding a reducing agent can accelerate the reaction rate, thereby improving the reaction efficiency and making the reaction more thorough.

[0024] The synthetic method of the present invention has the following beneficial effects: 1. The cardanol used in this technical solution is a type of natural phenolic compound from cereals or plants extracted from cashew nut shell liquid (CNSL). As a natural plant extract, the material cost is lower than that of the traditional production method; 2. This technical solution uses cardanol as a raw material, so that the original alkoxy group in the final product is replaced by the long carbon chain of cardanol, and the stability of the carbon chain is relatively strong, so that the benzotriazole ultraviolet absorber produced by this technical solution has strong weather resistance; 3. When coupling cardanol with diazo compound A, in order to increase the selectivity of the reaction position and reduce the generation of by-products, the present technical solution uses a diazotization reaction to first replace a nitro group on the benzene ring of cardanol, and then react the intermediate product with diazo compound A, thereby improving the selectivity of the reaction and significantly increasing the yield of the ortho-substituted product of cardanol.

[0025] Generally, the present invention recommends the following steps to synthesize benzotriazole ultraviolet absorbers: S1: Diazotization reaction: Add chloro-o-nitroaniline and dilute hydrochloric acid to the reactor, mix well, slowly add sodium nitrite solution under low temperature, and continue stirring to react to obtain diazo compound A. S2: Cardanol modification: Cardanol was mixed with 20% nitric acid, and stirred continuously under heating conditions for reaction, and then steam distilled to obtain the intermediate product nitrocardanol. S3: Coupling reaction: Add nitro-cashew phenol and liquid benzene to the reactor, add sodium hydroxide after they are completely dissolved, and slowly drop diazo liquid A under low temperature stirring to obtain intermediate product B. S4: Reduction reaction: Add intermediate product B and anhydrous ethanol to the reactor, stir evenly, add active zinc powder, slowly drop concentrated hydrochloric acid under stirring and heating conditions, and react to obtain intermediate product C S5: Synthesis of target product: Add intermediate product C, sodium nitrite, nitrous acid and dilute hydrochloric acid into the reactor, continue to stir the reaction, add hypophosphorous acid after the reaction is completed and heat to obtain the target product, cardanol-modified benzotriazole ultraviolet absorber. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is the liquid chromatogram of the target product of Example 2.

[0027] Figure 2 It is the liquid chromatogram of the target product of Comparative Example 2.

[0028] Figure 3 This is the NMR spectrum of the target product in Example 2. DETAILED DESCRIPTION

[0029] The present invention is further described below through specific implementation modes, but the protection scope of the present invention is not limited thereto.

[0030] Preparation Example 1: S1: Diazotization reaction: Add 173g of chloro-o-nitroaniline (1mol) and 500ml of dilute hydrochloric acid into a reaction kettle, mix well, then slowly drop 200g of 20% sodium nitrite solution under low temperature, and continue stirring to react to obtain diazo compound A. S2: Modification of cardanol: 380 g of cardanol (1.2 mol) was mixed with 20% nitric acid, and the mixture was stirred under heating conditions for reaction, and then steam distilled to obtain the intermediate product nitro cardanol. S3: Coupling reaction: Add nitro-cashew phenol and 500 ml of liquid benzene to the reactor. After they are completely dissolved, add 40 g of sodium hydroxide. Slowly drop diazo liquid A under low temperature stirring to obtain intermediate product B. S4: Reduction reaction: Add intermediate product B and 500 ml of anhydrous ethanol to the reactor, stir evenly, add 20 g of active zinc powder, slowly drop 200 ml of concentrated hydrochloric acid under stirring and heating conditions to obtain intermediate product C. S5: Synthesis of target product: Add intermediate product C, 500 ml of sodium nitrite nitrite solution and 100 ml of dilute hydrochloric acid into a reactor, continue stirring to react, add 50 g of hypophosphorous acid after the reaction is completed and heat to obtain the target product, cardanol-modified benzotriazole ultraviolet absorber.

[0031] The difference between Preparation Example 2 and Preparation Example 1 is that the raw material selected in step S2 of Preparation Example 2 is cashew nut monophenol.

[0032] The difference between Preparation Example 3 and Preparation Example 1 is that the substituted or unsubstituted o-nitroaniline selected in step S1 of Preparation Example 3 is o-nitroaniline.

[0033] The difference between Preparation Example 4 and Preparation Example 1 is that the substituted or unsubstituted o-nitroaniline selected in step S1 of Preparation Example 4 is bromo-o-nitroaniline.

[0034] The difference between Preparation Example 5 and Preparation Example 1 is that in Preparation Example 5, no reducing agent is added in step S5.

[0035] The difference between Preparation Example 6 and Example 1 is that the cardanol is not subjected to diazotization reaction treatment. The specific process is as follows: A1: Diazotization reaction: add 173g of chloro-o-nitroaniline (1mol) and 500ml of dilute hydrochloric acid to a reactor, mix well, slowly drop 200g of 20% sodium nitrite solution under low temperature conditions, and continue to stir to react to obtain diazo compound A. A2: Coupling reaction: add cashew diphenol and 500ml of liquid benzene to a reactor, add 40g of sodium hydroxide after complete dissolution, and slowly drop diazo liquid A under low temperature stirring conditions to obtain intermediate product B. A3: Reduction reaction: Add intermediate product B and 500 ml of anhydrous ethanol to the reactor, stir evenly, then add 20 g of active zinc powder, slowly dropwise add 200 ml of concentrated hydrochloric acid under stirring and heating conditions to obtain intermediate product C.

[0036] The difference between Preparation Example 7 and Preparation Example 6 is that the raw material selected in Step A2 is cashew nut monophenol.

[0037] The modified polyester particles were prepared by mixing the various examples and comparative examples in the proportions shown in the following table: The adhesive is polyurethane resin, and the dispersant is composed of sodium hexametaphosphate and glyceryl stearate in a weight ratio of 1:2. The adhesive and dispersant do not have ultraviolet absorption function.

[0038] Detection Methods Liquid chromatography was used to perform liquid phase analysis on the products of each preparation example to obtain the purity and yield of each product.

[0039] The modified polyester particles prepared in each embodiment and comparative example were melt-drawn and woven into fabrics for ultraviolet irradiation experiments to obtain the ultraviolet absorption rates of each embodiment and comparative example.

[0040] The modified polyester particles prepared in each embodiment and comparative example were melt-drawn and woven into fabrics for a long-term ultraviolet irradiation experiment to observe the color changes of each embodiment and comparative example.

[0041] The test results are shown in the following table: Product purity (%) Product yield (%) Example 1 99.4 81.3 Example 2 96.5 79.6 Example 5 84.9 73.8 Comparative Example 1 88.1 80.2 Comparative Example 2 76.4 74.1 Conclusion: According to the data of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 in the above table, when synthesizing benzotriazole ultraviolet absorbers, the raw material cardanol is first subjected to diazotization treatment, and a nitro group is first substituted on the benzene ring of cardanol, and then the intermediate product is reacted with substituted or unsubstituted o-nitroaniline, thereby improving the selectivity of the reaction, and greatly increasing the yield of the ortho-substituted product of cardanol, thereby improving the purity and yield of the reaction product. However, in the traditional synthesis method, there is no such treatment step, so that the yield and purity of the traditional synthesis method are low. At the same time, the product yield and purity of cashew diphenol as the raw material are greater than the product yield and purity of cashew monophenol as the raw material. This is due to the positioning effect of the two hydroxyl groups on cashew bisphenol, which makes it When it is substituted with substituted or unsubstituted o-nitroaniline, the position of substitution is relatively determined, and there is only one hydroxyl group on the benzene ring of cashew monophenol, and the positioning is not obvious. It is easy to produce more by-products during the reaction, and a diazotization reaction is required to achieve the positioning effect.

[0042] Conclusion: It can be seen from the data of Example 1 and Example 5 in the above table that the purity and yield of the product are significantly increased after the reducing agent is added in step 5 of the present technical solution. This is because the presence of the reducing agent can accelerate the decomposition of the substituents on the benzene ring, which is more efficient than thermal decomposition. UV transmittance (%) Horizontal return angle (°) Example 1 0.2 179 Example 2 0.8 175 Comparative Example 1 12.1 126 Comparative Example 2 15.9 112 Comparative Example 3 0.5 177

[0043] Conclusion: It can be seen from the data of Example 1 and Comparative Example 3 in the above table that the benzotriazole ultraviolet absorber produced by the present technical scheme has not only lower ultraviolet transmittance but also higher horizontal recovery angle than the commercially available benzotriazole ultraviolet absorbers, which indicates that the benzotriazole ultraviolet absorber produced by the present technical scheme has relatively excellent ultraviolet absorption function and meets the requirements on the market.

[0044] Conclusion: It can be seen from the data of Example 1 and Example 2 in the above table that when the benzotriazole ultraviolet absorber is produced by the present technical scheme, the ultraviolet absorption function of the ultraviolet absorber produced by using cashew diphenol as the raw material is better than that of the ultraviolet absorber produced by using cashew monophenol as the raw material. This is because the principle of benzotriazole ultraviolet absorbers absorbing ultraviolet rays is that the hydroxyl group on the benzene ring and the nitrogen ring form a chelate ring composed of intramolecular hydrogen bonds. After absorbing ultraviolet light, the intramolecular hydrogen bonds are destroyed to form unstable high-energy ionic compounds. When not irradiated by ultraviolet rays, excess energy is released to restore the original low-energy stable state, thereby absorbing ultraviolet light. Therefore, the ultraviolet absorption function of the ultraviolet absorber produced by using cashew diphenol containing two hydroxyl groups on the benzene ring as the raw material is better.

[0045] Conclusion: It can be seen from the data of Example 1 and Comparative Example 3 in the above table that the benzotriazole ultraviolet absorber produced by the present technical scheme can still maintain white color under long-term ultraviolet irradiation, and does not turn yellow until 48 hours of continuous irradiation, compared with the commercially available benzotriazole ultraviolet absorber. The commercially available benzotriazole ultraviolet absorber turns yellow after 24 hours of irradiation, and the yellow color is very obvious after 48 hours of continuous irradiation, indicating that the benzotriazole ultraviolet absorber produced by the present technical scheme has excellent weather resistance and can be used for objects that need to be exposed to the sun for a long time. This is because by using cardanol as a raw material, the original alkoxy group in the final product is replaced by the long carbon chain of cardanol, and the carbon chain is more stable, so that the benzotriazole ultraviolet absorber produced by the present technical scheme has stronger weather resistance.

[0046] Conclusion: It can be seen from the data of Example 1, Example 3 and Example 4 in the above table that when the substituent on o-nitroaniline is chlorine, the produced UV absorber has good weather resistance, and the modified polyester particles added with the UV absorber can still remain white under long-term ultraviolet rays, indicating that in this technical solution, it is more appropriate to use chloro-o-nitroaniline as a raw material.

[0047] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for synthesizing a benzotriazole ultraviolet absorber modified by plant extract cardanol, characterized in that: The steps include: S1: Diazotization reaction: Add substituted or unsubstituted o-nitroaniline and dilute hydrochloric acid to the reactor, mix well, slowly add sodium nitrite solution dropwise under low temperature, and continue stirring to react to obtain diazo compound A. S2: Cardanol modification: Cardanol was mixed with 20% nitric acid, and stirred continuously under heating conditions for reaction, and then steam distilled to obtain the intermediate product nitrocardanol. S3: Coupling reaction: Add nitrocardanol and organic solvent to the reactor, add alkaline catalyst after complete dissolution, slowly drop diazo liquid A under low temperature stirring condition, and react to obtain intermediate product B. S4: Reduction reaction: Add intermediate product B and anhydrous ethanol to the reactor, stir evenly, add metal catalyst, slowly drop concentrated hydrochloric acid under stirring and heating conditions, and react to obtain intermediate product C. S5: Synthesis of target product: Add intermediate product C, sodium nitrite, nitrous acid and dilute hydrochloric acid into the reactor, continue to stir the reaction, add a reducing agent after the reaction is completed and heat to obtain the target product, cardanol-modified benzotriazole ultraviolet absorber.

2. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 1, characterized in that: The substituted or unsubstituted o-nitroaniline in step S1 includes one or a combination of o-nitroaniline, chloro-o-nitroaniline and bromo-o-nitroaniline.

3. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 2, characterized in that: The substituted or unsubstituted o-nitroaniline in step S1 is chloro-o-nitroaniline.

4. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 1, characterized in that: The cardanol in step S2 includes one or more combinations of cardanol and cardanol diphenol, and the structure of the cardanol is as follows: (R=-C 15 H 31-2n , where n = 0 to 3) The structure of the cashew nut diphenol is shown below: (R=C 15 ~C 17 , containing 1-3 double bonds).

5. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 4, characterized in that: The cardanol in step S2 is cardanol.

6. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 1, characterized in that: The metal catalyst in step S3 is one or a combination of active iron powder and active zinc powder.

7. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 1, characterized in that: The reaction temperature in steps S1 and S3 is 0-5°C.

8. The method for synthesizing a plant extract cardanol-modified benzotriazole ultraviolet absorber according to claim 1, characterized in that: The reducing agent in step S5 is one or a combination of phosphorous acid and hypophosphorous acid.

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