Environmentally friendly organic pigment and preparation method thereof

Abstract

The invention discloses a kind of environment-friendly organic pigment and preparation method thereof, belong to the field of organic pigment technology, comprise the following steps: S1, adopt TLC method to monitor whether diazotization reaction is completed, monitor to the completion of reaction, reactant liquor is subjected to nanofiltration treatment, remove unreacted sodium nitrite and sodium sulfate, obtain the diazonium salt after nanofiltration treatment;S2, the diazonium salt after nanofiltration treatment and 5 acetoacetamido benzimidazolone are mixed in microchannel reactor, after mixing, add weak acid, then temperature jump is increased to 85 DEG C, the diazonium salt after nanofiltration treatment and 5 acetoacetamido benzimidazolone carry out coupling reaction, filter washing, dry after pulverizing, obtain pigment crude product. The purity of the environment-friendly organic pigment finally prepared by the present invention is high, safe and environmentally friendly to environment and people, does not contain 24 kinds of aromatic amines with carcinogenicity.

Description

Technical Field

[0001] The present invention relates to the technical field of organic pigments, and in particular to an environmentally friendly organic pigment and a preparation method thereof. Background Art

[0002] Pigment printing pastes are made by mechanically grinding pigments (colorants), dispersants, wetting agents, and water. With the exception of carbon black (black) and titanium dioxide (white), all other colorants are organic pigments. Organic pigments are categorized by their chemical structure into azo pigments (>50%), heterocyclic pigments (<11%), and phthalocyanine pigments (29%). Azo pigments are the most widely used, primarily in yellow, orange, and red colors. Heterocyclic pigments are primarily red and purple, while phthalocyanine pigments are primarily blue and green. Azo pigments are primarily affected by carcinogenic aromatic amines. According to the Colour Index, 56 organic pigments are affected by carcinogenic aromatic amines, of which 25 (44.6%) are 3,3'-dichlorobenzidine (DCB), affecting the majority of yellow and orange pigments. The International Agency for Research on Cancer (IARC) has designated DCB as a carcinogenic chemical.

[0003] There are three main amines: 3,3'-dichlorobenzidine (DCB), 3,3'-dimethylbenzidine (DMB), and 2-methyl-5-nitroaniline (Brilliant Red G color base). Seven organic pigments are implicated: CI Pigment Yellow 12 (Benzidine Yellow G), CI Pigment Yellow 16 (Permanent Yellow 7G), CI Pigment Yellow 17 (Permanent Yellow 2G), CI Pigment Yellow 77 (Permanent Golden GR), CI Pigment Orange 13 (Permanent Orange G), CI Pigment Red 8 (Permanent Red F4R), and CI Pigment Red 22 (Brilliant Red G). However, most organic pigments inevitably contain trace amounts of unreacted aromatic amine residues, and organic pigments synthesized from DCB can also contain DCB exceeding the limit of 30 mg / kg. There are numerous cases where DCB content in organic pigments synthesized from DCB has exceeded the limit in the processing and pigment printing of fabrics. During the preparation of organic pigments, in the diazo reaction step, sodium nitrite is unstable under acidic conditions, which will generate nitric oxide gas. Nitric oxide will react with oxygen to generate nitrogen dioxide, which will be released and pollute the environment. In addition, if the amount of sodium nitrite used is too much, it will oxidize the aromatic amine, consume the acid, increase the side reactions in the coupling reaction step, and cause the diazonium salt itself to decompose. Summary of the Invention

[0004] In order to overcome the shortcomings of the prior art, one of the purposes of the present invention is to provide a method for preparing an environmentally friendly organic pigment. The prepared environmentally friendly organic pigment has high purity, is safe and environmentally friendly to the environment and humans, and does not contain 24 carcinogenic aromatic amines.

[0005] A second object of the present invention is to provide an environmentally friendly organic pigment.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] An environmentally friendly organic pigment comprises the following steps: S1, subjecting a substituted aromatic amine, sulfuric acid, and excess sodium nitrite to a diazotization reaction at a reaction temperature of 0 to 5°C to generate a diazonium salt, monitoring the completion of the diazotization reaction by TLC, and after completion of the reaction, subjecting the reaction solution to nanofiltration to remove unreacted sodium nitrite and sodium sulfate, thereby obtaining a nanofiltered diazonium salt;

[0008] S2, mixing the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone in a microchannel reactor, adding a weak acid after mixing, and then increasing the temperature to 85 ° C., the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are coupled to react, filtered, washed, dried and crushed to obtain a crude pigment;

[0009] S3, wetting cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, adding the crude pigment to the cellulose nanocrystal (CNCs) colloid to obtain an environmentally friendly benzimidazolone organic pigment suspension, and ultrasonically stirring and dispersing the environmentally friendly benzimidazolone organic pigment suspension with a cell crusher to obtain the environmentally friendly benzimidazolone organic pigment;

[0010] The general structural formula of the substituted aromatic amine is as follows:

[0011]

[0012] X is selected from one of CH3, Cl, NO2, and SO3H; Y is selected from one of OCH3, H, and NO2.

[0013] Furthermore, in step S1, the molar ratio of the substituted aromatic amine to the sulfuric acid is 1:2.5-4.

[0014] Furthermore, in step S2, after adding the weak acid, the pH of the solution is 4-7.

[0015] Furthermore, in step S2, the weak acid is one of acetic acid or citric acid.

[0016] Furthermore, in step S3, the crude pigment is added to the cellulose nanocrystals (CNCs) colloid, and the mass ratio of the crude pigment to the cellulose nanocrystals is 1:1.

[0017] The second object of the present invention is to provide an environmentally friendly organic pigment prepared by the above-mentioned preparation method.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] (1) The present invention provides a method for preparing an environmentally friendly organic pigment. The present invention uses non-carcinogenic aromatic amines to prepare diazonium salts, and 5-acetoacetamidobenzimidazolone is used as a coupling component. Twenty-four carcinogenic aromatic amines will not be generated during the preparation and detection of the organic pigment. After the diazonium salt is generated, the TLC method is used to monitor whether the diazotization reaction is completed. After the reaction is completed, the reaction solution is subjected to nanofiltration treatment to remove unreacted sodium nitrite and sodium sulfate, so that the diazotization reaction is terminated and the stability of the diazonium salt is maintained. No side reactions will occur during the diazotization reaction to generate by-products, which will increase the side reactions of the subsequent coupling reaction and reduce the difficulty of purifying the organic pigment. In addition, because too much sodium nitrite is used in the diazotization reaction, the oxidizing property of sodium nitrite will also cause the diazonium salt itself to decompose.

[0020] (2) The present invention provides a method for preparing an environmentally friendly organic pigment. The microchannel reactor has excellent mass and heat transfer performance. The diazonium salt treated by nanofiltration and 5-acetoacetamidobenzimidazolone are mixed in the microchannel reactor. After mixing, a weak acid is added, and then the temperature is increased to 85°C, which exceeds the temperature range of 70°C to 80°C where the diazonium salt is easily decomposed and coupled, thereby avoiding the side reaction of coupling between the diazonium salts.

[0021] (3) The present invention provides a method for preparing an environmentally friendly organic pigment, in which a crude pigment is added to a cellulose nanocrystal (CNCs) colloid. The existing method for preparing organic pigments usually disperses the crude pigment in an organic phase, such as a trichlorobenzene solvent. However, most organic phases are volatile, harmful to the environment and organisms, and unsafe and environmentally friendly. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be noted that, under the premise of no conflict, the embodiments or technical features described below can be arbitrarily combined to form new embodiments.

[0023] Cellulose nanocrystals (CNCs) powder was purchased from ScienceK Co., Ltd (Huzhou);

[0024] The microchannel reactor was a Corning high-throughput microchannel G1 reactor;

[0025] The ultrasonic crusher was purchased from Ningbo Xinzhi.

[0026] Example 1

[0027] This embodiment provides a method for preparing an environmentally friendly organic pigment, comprising the following steps: S1, subjecting a substituted aromatic amine in a molar ratio of 1:2.5 to a diazotization reaction with sulfuric acid and an excess of sodium nitrite at a reaction temperature of 0° C. to generate a diazonium salt, monitoring the completion of the diazotization reaction by TLC, and after the reaction is completed, subjecting the reaction solution to nanofiltration to remove unreacted sodium nitrite and sodium sulfate, thereby obtaining a nanofiltered diazonium salt;

[0028] S2, the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are mixed in a microchannel reactor, and after mixing, acetic acid is added, the pH of the solution is 4, and then the temperature is increased to 85 ° C., the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are coupled to react, filtered, washed, dried and crushed to obtain a crude pigment;

[0029] S3, wetting cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, adding a crude pigment to the cellulose nanocrystal (CNCs) colloid to obtain an environmentally friendly benzimidazolone organic pigment suspension, and ultrasonically stirring and dispersing the environmentally friendly benzimidazolone organic pigment suspension using a cell crusher to obtain an environmentally friendly benzimidazolone organic pigment;

[0030] The general structural formula of the substituted aromatic amine is as follows:

[0031]

[0032] Example 2

[0033] This embodiment provides a method for preparing an environmentally friendly organic pigment, comprising the following steps:

[0034] S1. A substituted aromatic amine in a molar ratio of 1:3 is subjected to a diazotization reaction with sulfuric acid and an excess of sodium nitrite at a reaction temperature of 5° C. to generate a diazonium salt. The completion of the diazotization reaction is monitored by TLC. After the completion of the reaction is detected, the reaction solution is subjected to nanofiltration to remove unreacted sodium nitrite and sodium sulfate, thereby obtaining a diazonium salt after nanofiltration.

[0035] S2, the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are mixed in a microchannel reactor, and after mixing, citric acid is added, the pH of the solution is 5, and then the temperature is increased to 85 ° C., the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are coupled to react, filtered, washed, dried and crushed to obtain a crude pigment;

[0036] S3, wetting cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, adding a crude pigment to the cellulose nanocrystal (CNCs) colloid to obtain an environmentally friendly benzimidazolone organic pigment suspension, and ultrasonically stirring and dispersing the environmentally friendly benzimidazolone organic pigment suspension using a cell crusher to obtain an environmentally friendly benzimidazolone organic pigment;

[0037] The general structural formula of the substituted aromatic amine is as follows:

[0038]

[0039] Example 3

[0040] This embodiment provides a method for preparing an environmentally friendly organic pigment, comprising the following steps:

[0041] S1. A substituted aromatic amine in a molar ratio of 1:4 is subjected to a diazotization reaction with sulfuric acid and an excess of sodium nitrite at a reaction temperature of 3° C. to generate a diazonium salt. The completion of the diazotization reaction is monitored by TLC. After the completion of the reaction is detected, the reaction solution is subjected to nanofiltration to remove unreacted sodium nitrite and sodium sulfate, thereby obtaining a diazonium salt after nanofiltration.

[0042] S2, the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are mixed in a microchannel reactor, and after mixing, acetic acid is added, the pH of the solution is 7, and then the temperature is increased to 85 ° C., the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone are coupled to react, filtered, washed, dried and crushed to obtain a crude pigment;

[0043] S3, wetting cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, adding a crude pigment to the cellulose nanocrystal (CNCs) colloid to obtain an environmentally friendly benzimidazolone organic pigment suspension, and ultrasonically stirring and dispersing the environmentally friendly benzimidazolone organic pigment suspension using a cell crusher to obtain an environmentally friendly benzimidazolone organic pigment;

[0044] The general structural formula of the substituted aromatic amine is as follows:

[0045]

[0046] X is selected from one of CH3, Cl, NO2, and SO3H; Y is selected from one of OCH3, H, and NO2.

[0047] Example 4

[0048] This embodiment provides a method for preparing an environmentally friendly organic pigment, comprising the following steps:

[0049] S1. Performing a diazotization reaction on a substituted aromatic amine with sulfuric acid and an excess of sodium nitrite at a reaction temperature of 0 to 5° C. to generate a diazonium salt. The completion of the diazotization reaction is monitored by TLC. After the completion of the reaction is detected, the reaction solution is subjected to nanofiltration to remove unreacted sodium nitrite and sodium sulfate to obtain a nanofiltration-treated diazonium salt.

[0050] S2, mixing the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone in a microchannel reactor, adding citric acid after mixing, and then increasing the temperature to 85° C., and performing a coupling reaction between the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone, filtering, washing, drying and crushing to obtain a crude pigment;

[0051] S3, wetting cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, adding a crude pigment to the cellulose nanocrystal (CNCs) colloid to obtain an environmentally friendly benzimidazolone organic pigment suspension, and ultrasonically stirring and dispersing the environmentally friendly benzimidazolone organic pigment suspension using a cell crusher to obtain an environmentally friendly benzimidazolone organic pigment;

[0052] The general structural formula of the substituted aromatic amine is as follows:

[0053]

[0054] Experimental example

[0055] 100 g of each sample of the environmentally friendly organic pigment provided in Examples 1 to 4 was taken and the aromatic amine content was tested by gas chromatography-mass spectrometry according to the EN 14362-1:2012(E) method. The test results were 97 ppm as shown in Table 1.

[0056] Table 1 Aromatic amine content detected in an environmentally friendly organic pigment provided in Examples 1 to 4

[0057] Group Example 1 Example 2 Example 3 Example 4 Aromatic amine content (g) 0.05 0.12 0.15 0.08

[0058] As shown in Table 1, the aromatic amine content detected in the environmentally friendly organic pigment provided in Examples 1 to 3 is all around 0.1 g, indicating that the aromatic amine content of the environmentally friendly organic pigment prepared by the preparation method of the environmentally friendly organic pigment provided by the present invention is around 0.1%, which is extremely low and environmentally friendly and safe for users and the environment.

[0059] The above embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and replacements made by technicians in this field on the basis of the present invention fall within the scope of protection required by the present invention.

Claims

1. A method for preparing an environmentally friendly benzimidazolone organic pigment, characterized in that: The following steps are involved: S1. Performing a diazotization reaction on a substituted aromatic amine, sulfuric acid, and an excess of sodium nitrite at a reaction temperature of 0 to 5° C. to generate a diazonium salt. The completion of the diazotization reaction is monitored by TLC. After the completion of the reaction is detected, the reaction solution is subjected to nanofiltration to remove unreacted sodium nitrite and sodium sulfate to obtain a nanofiltration-treated diazonium salt. S2, mixing the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone in a microchannel reactor, adding a weak acid after mixing, and then increasing the temperature to 85 ° C., the nanofiltration treated diazonium salt and 5-acetoacetamidobenzimidazolone undergo a coupling reaction, filtering, washing, drying and crushing to obtain a crude pigment; S3, wetting cellulose nanocrystals (CNCs) as a dispersant and stabilizer with ethanol to obtain a cellulose nanocrystal (CNCs) colloid, adding the crude pigment to the cellulose nanocrystal (CNCs) colloid to obtain an environmentally friendly benzimidazolone organic pigment suspension, and ultrasonically stirring and dispersing the environmentally friendly benzimidazolone organic pigment suspension with a cell crusher to obtain the environmentally friendly benzimidazolone organic pigment; The general structural formula of the substituted aromatic amine is as follows: X is selected from one of CH3, Cl, NO2, and SO3H; Y is selected from one of OCH3, H, and NO2.

2. The method for preparing an environmentally friendly benzimidazolone organic pigment according to claim 1, wherein: In step S1, the molar ratio of the substituted aromatic amine to the sulfuric acid is 1:2.5-4.

3. The method for preparing an environmentally friendly benzimidazolone organic pigment according to claim 1, wherein: In step S2, after adding a weak acid, the pH of the solution is 4-7.

4. The method for preparing an environmentally friendly benzimidazolone organic pigment according to claim 1, wherein: In step S2, the weak acid is one of acetic acid or citric acid.

5. The method for preparing an environmentally friendly benzimidazolone organic pigment according to claim 1, wherein: In step S3, the crude pigment is added to the cellulose nanocrystals (CNCs) colloid, and the mass ratio of the crude pigment to the cellulose nanocrystals is 1:

40.

6. An environmentally friendly benzimidazolone organic pigment prepared by the preparation method of an environmentally friendly benzimidazolone organic pigment according to any one of claims 1 to 5.