Carbazole modified acrylate polymer as well as preparation method and application thereof

Abstract

The invention discloses a carbazole modified acrylate polymer, a preparation method and application thereof, and belongs to the technical field of anode electrophoretic paint. The structural formula of the carbazole modified acrylate polymer is as follows: # imgabs0 #, the substance is neutralized by organic alkali to obtain an anionic polymer corrosion inhibitor with carboxyl, and the anionic polymer corrosion inhibitor is compounded with other micromolecular corrosion inhibitors to serve as an additive to be uniformly dispersed in a water-ethylene glycol system to obtain the additive-containing anodic electrophoretic paint. According to the present invention, the metal substrate has characteristics of good electrochemical corrosion resistance and certain fluorescence property, such that the purpose of forming the film with characteristics of uniform thickness, good adhesion, good solvent resistance and cross-linked network structure on the metal substrate so as to prevent the electrochemical corrosion of the metal is achieved.

Description

Technical Field

[0001] The present invention relates to a preparation method and application of an acrylate polymer fluorescent material, belonging to the technical field of anodic electrophoretic paint. Background Art

[0002] Electrophoretic coating is a coating method that uses an externally applied electric field to drive pigments, resins, and other particles suspended in an electrophoretic solution to migrate directionally and deposit on the electrode surface to form a uniform and dense coating. Electrophoretic coating can cover workpieces with complex geometries, such as automobile bodies, and the coating thickness is controllable with excellent adhesion. The electrophoretic paint directly affects the coating efficiency and final performance. Electrophoretic paints are classified into anodic electrophoretic paints and cathodic electrophoretic paints according to the deposition method. The former uses the workpiece as the anode to attract negatively charged paint particles, and the latter adsorbs positively charged paint particles with the workpiece as the cathode. Anodic electrophoretic paints are low-cost and have a mature process. They were widely used in the field of metal anti-corrosion in the early stage, but their corrosion resistance is relatively weak, which has promoted the continuous optimization of the material system.

[0003] With the improvement of environmental protection and performance requirements, acrylic resins have gradually become the mainstream of anodic electrophoretic paints. Acrylic resins are polymerized from acrylate monomers, and their molecular chains are rich in polar groups such as carboxyl groups. Anionic polymers are obtained by neutralizing carboxyl groups with organic bases and can be dispersed in water. By designing the types and proportions of monomers, the glass transition temperature, acid value, and stability of the resin can be changed, thereby optimizing the mechanical properties and chemical resistance of the coating.

[0004] The breakthrough progress of acrylic anodic electrophoretic paints is reflected in the field of functional modification. The salt spray resistance and wear resistance of the coating have been significantly improved by grafting fluorine-containing monomers or compounding with nanoparticles. In addition, the development of low-temperature curing technology reduces the risk of thermal deformation of the substrate while reducing energy consumption. At the environmental protection level, the waterborne acrylic system replaces the solvent-based formulation, and the VOC emissions are reduced by more than 80%, meeting the trend of green manufacturing. Currently, the application fields of acrylic anodic electrophoretic paints include automotive parts, household appliances, hardware, decorations, aluminum profiles, etc.

[0005] Based on the above background, the present invention uses carbazole-modified acrylate polymers. Firstly, heteroatoms are introduced through chemical modification to improve the electrochemical anti-corrosion performance of acrylate polymers for different metals. Secondly, crosslinkable carbazole groups are introduced, so that the deposited electrophoretic paint film has a crosslinked network structure. Thirdly, a planar conjugated structure is introduced, so that the polymer has a fluorescent function for characterizing the film-forming performance. Summary of the Invention

[0006] The object of the present invention is to use acrylate polymers as the main body, and by introducing carbazole monomers into the polymers, a method for preparing a polymer material with fluorescent function is provided, and then a film is prepared, which has excellent electrochemical anti-corrosion performance, mechanical properties, and fluorescent properties.

[0007] The present invention is achieved by the following technical methods:

[0008] A carbazole-modified acrylate polymer, the polymer structural formula is as follows:

[0009]

[0010] There is no special restriction on the ratio of m, n, and o, which can be adjusted according to needs. For example, the molar ratio of polymer feed is m∶n∶o = (5 - 30)∶(1 - 15)∶(0.01 - 5).

[0012] In polymer structural formula m, the corresponding R1 substituent is a straight-chain alkyl group, such as -(CH2) n -CH3, where n = 0 - 10, and when n = 0, it corresponds to a methyl group; or a branched-chain alkyl group with C4 - C12, or an alkyl chain containing a hydroxyl substituent (the alkyl chain is preferably the above-mentioned straight-chain alkyl group or branched-chain alkyl group). In m, R2 is a hydrogen atom or a methyl group; in n, R3 is a hydrogen atom or a methyl group; in n, R4 is an alkyl chain, such as -(CH2) n -, n = 0 - 5, or an alkyl chain containing an ester group, such as -COO-(CH2) n -, n = 0 - 5.

[0013] The preparation method of the above-mentioned carbazole-modified acrylate polymer includes the following steps:

[0014] Using the free radical polymerization method, the solvent can be an organic solvent such as isopropyl alcohol, n-butyl alcohol, ethanol, acetone, N,N-dimethylformamide, etc. The initiator is an azo compound. All monomers and the initiator are ultrasonically treated in an ice-water bath to be mixed evenly, and then heated for reaction. The reaction temperature is set to be about 5°C lower than the boiling point of the used solvent. After reacting for a period of time, a carbazole-modified acrylate polymer is obtained;

[0015] The monomers include the following:

[0016]

[0017] The above polymer is used in an anticorrosive coating, and is further compounded with benzotriazole for use in an anticorrosive coating; the mass ratio of benzotriazole to the polymer is (1 - 5)∶5.

[0018] A preparation method of an additive-containing anodic electrophoretic paint includes the following steps:

[0019] First, use organic bases containing amino groups such as N,N-dimethylethanolamine and triethylamine to neutralize the carboxyl groups in the polymer to form an anionic polymer with carboxyl groups. The degree of neutralization can be adjusted according to actual needs. The degree of neutralization is defined as the ratio of the amount of substance of amino groups in the neutralizing base to the amount of substance of carboxyl groups in the polymer (preferably, the molar percentage of neutralized carboxyl groups in the original total carboxyl groups is 50-100%); Take out the neutralized anionic polymer with carboxyl groups and disperse it evenly in a water-ethylene glycol system (water:

[0020] The volume ratio of ethylene glycol is preferably 2:3), and add benzotriazole for compounding to obtain anodic electrophoretic paint containing additives; The mass ratio of benzotriazole to the polymer is (1-5):5; The mass percentage concentration of the anionic polymer with carboxyl groups in the water-ethylene glycol system is 0.2-10 g / L, preferably 0.5-5 g / L;

[0021] Use the above anodic electrophoretic paint containing additives to deposit a protective film on the surface of the metal substrate. The anode is the metal substrate, and the cathode is a platinum sheet. Apply electricity at 30 V for 1-5 h, and a relatively dense film is deposited on the anode metal substrate.

[0022] The above method can be applied to the field of metal surface coating, such as automobiles, household appliances, and building materials, etc.

[0023] As is well known, carbazole has a rigid planar conjugated structure, so it can bring certain fluorescence properties to the polymer. In addition, the electrochemical polymerization property possessed by carbazole itself helps the cross-linking between polymers, further improving the thermal stability of the polymer, being beneficial for use in high-temperature environments, and the deposited electrophoretic paint film is a cross-linked network structure, improving the solvent resistance of the paint film. The said film is a corrosion-resistant film; The integrity of the film can be detected by fluorescence.

[0024] Advantages of the present invention:

[0025] The carbazole-modified acrylate polymer synthesized by the above method has a simple synthesis step and is suitable for large-scale production. It can be used as an additive and compounded with organic small molecule corrosion inhibitors for anodic electrophoretic paint, having good electrochemical corrosion prevention performance for various metals. And the carbazole-modified acrylate polymer has a fluorescence function, and can further improve the thermal stability of the polymer, being beneficial for use in high-temperature environments. When the carbazole-modified acrylate polymer is used as an additive for anodic electrophoretic paint, electrochemical cross-linking occurs during the film-forming process by applying electricity at room temperature, forming a cross-linked network structure, improving the solvent resistance of the paint film, and being more suitable for the preparation of anticorrosive coatings. Compared with traditional thermosetting acrylic resins, cross-linking can occur without heating, reducing energy consumption and being more environmentally friendly. Description of the Drawings

[0026] Figure 1Schematic structural diagram of N-vinylcarbazole modified acrylate polymer.

[0027] Figure 2 Nuclear magnetic spectrum of N-vinylcarbazole modified acrylate polymer.

[0028] Figure 3 Ultraviolet absorption diagram of polymers with different N-vinylcarbazole feeding ratios.

[0029] Figure 4 Steady-state fluorescence spectrum of N-vinylcarbazole modified acrylate polymer after film formation on different metal specimens.

[0030] Figure 5 I-T curve diagram of N-vinylcarbazole modified acrylate polymer on different metal specimens.

[0031] Figure 6 TEM diagram of N-vinylcarbazole modified acrylate polymer as an additive for anodic electrophoretic paint in the dispersion.

[0032] Figure 7 SEM diagram of N-vinylcarbazole modified acrylate polymer as an additive for anodic electrophoretic paint after electrodeposition film formation. Detailed implementation mode

[0033] The present invention will be further described below in conjunction with embodiments, but the present invention is not limited to the following embodiments.

[0034] Example 1

[0035] As Figure 1 shown, the free radical polymerization method is adopted, isopropanol is used as the solvent, and azobisisobutyronitrile is used as the initiator. The m monomers include three kinds, namely m1 methyl methacrylate, m2 isooctyl acrylate, and m3 2-hydroxyethyl methacrylate, the n monomer is acrylic acid, and the o monomer is N-vinylcarbazole. All monomers (the molar ratio of monomer m: monomer n: monomer o is 20:5:0.14, and the molar ratio of monomer m1: monomer m2: monomer m3 is 6:1:3) and the initiator are ultrasonically treated in an ice-water bath to make them evenly mixed. The experimental device includes: an electric heating mantle, a polytetrafluoroethylene stirring paddle, a constant pressure dropping funnel, and a thermometer. The temperature of the electric heating mantle is set to 80 °C. When it is heated to 80 °C, it is added dropwise into a five-necked flask containing the solvent isopropanol through the constant pressure dropping funnel within a certain time, and finally kept warm for a certain time. Then the heating mantle and the stirrer are turned off. After waiting for it to cool to room temperature, the product is discharged to obtain the carbazole modified acrylate polymer (NVC-AR). The feeding mass ratio of all monomers to the solvent is 1:1.

[0036] The above polymer was purified by reprecipitation with petroleum ether and tetrahydrofuran, and white powder was obtained after drying in vacuo at 40 °C. Taking the polymer with the molar ratio of o monomer feed of 0.14 as an example. 15 mg of the purified polymer was dissolved in 0.6 ml of deuterated dimethyl sulfoxide for 1H NMR test, as Figure 2 shown. * is the solvent peak of deuterated dimethyl sulfoxide, # and # is the water peak. It was found that a total of 7 groups of peaks appeared in the spectrum. After integrating the hydrogens in the polymer structure, it was found that the integral area ratio was basically consistent with the ratio of the corresponding hydrogen numbers. Among them, the monomer peak area ratio of monomer o∶monomer n∶monomer m3∶(monomer m1 + monomer m2) in the copolymer was about 1∶32∶24∶120, which was consistent with the feed molar ratio, indicating that the polymer segments had been formed. And the group of peaks (A) with chemical shift at 8.5 - 7.0 proved that the carbazole monomer was successfully grafted onto the polymer segments.

[0037] Example 2

[0038] Polymers with the molar ratio of monomer m2 to monomer o of 1∶(0, 0.14, 0.29, 0.43, 0.58, 0.72) were named 0NVC-AR, 0.14NVC-AR, 0.29NVC-AR, 0.43NVC-AR, 0.58NVC-AR, and 0.72NVC-AR respectively. Polymers with different carbazole feed ratios after neutralization (neutralization carboxyl ratio of 70%) at a concentration of 2 g / L were dispersed in a water-ethylene glycol system, and the curves obtained from UV absorption tests were as Figure 3 shown. The UV curves were plotted using Origin software, and four peaks could be obtained. The absorption of the carbazole-modified acrylate polymer at 262 nm corresponded to the π-π * electronic transition of the benzene ring in the carbazole group, the absorption peak at 292 nm corresponded to the n-π* electronic transition in the carbazole matrix, and the absorption peaks at 328 nm and 342 nm represented intramolecular transition absorption, that is, the electron transfer of S0 - S1 between conjugated molecules. It can be seen that compared with the unmodified one, the UV absorption peaks of the carbazole-modified acrylate polymer came from carbazole itself. And with the increase of the carbazole feed ratio, a hyperchromic effect occurred, further proving the successful preparation of the carbazole-modified acrylate polymer.

[0039] Example 3

[0040] After compounding 0.29NVC-AR with a concentration of 5 g / L after neutralization (neutralization carboxyl ratio of 70%) and copper corrosion inhibitor - benzotriazole, the mass ratio of benzotriazole to the polymer was 3∶5, and it was dispersed in a water-ethylene glycol system. At this time, the anode was a metal specimen and the cathode was a platinum sheet. After energizing at 30 V for 3 h, a relatively dense film was deposited on the anode metal specimen. After air drying at room temperature, steady-state fluorescence spectrum test was carried out.

[0041] The steady-state fluorescence spectra obtained when the excitation wavelength was 310 nm and the slit was 1 nm are as follows Figure 4 shown. Due to the grafting of the carbazole fluorescent group, the films deposited on the zinc, tin, lead, and copper metal specimens also have fluorescence properties. The fluorescence spectra indicate that the carbazole-modified acrylate polymer was successfully deposited on the four anodic metal specimens of zinc, tin, lead, and copper.

[0042] Example 4

[0043] To further confirm that the compounding of the carbazole-modified acrylate polymer and benzotriazole has a good electrochemical anti-corrosion effect on anodic metals, an I-T curve test was carried out. After compounding the neutralized (the carboxyl group neutralization ratio was 70%) carbazole-modified acrylate polymer with a concentration of 5 g / L and the copper corrosion inhibitor - benzotriazole, it was dispersed in a water-ethylene glycol system. It was connected to the I-T curve test device. Taking copper metal as an example, the test conditions were a voltage of 30 V and a time of 3 h. As Figure 5 shown, the current of 0NVC-AR was about 10 -4 A at 10800 s, while the current of 0.29NVC-AR was about 10 -5 A at 10800 s. It can be seen that the electrochemical anti-corrosion effect of the carbazole-modified acrylate polymer on copper metal has been greatly improved.

[0044] Example 5

[0045] As Figure 6 shown, 5 g / L of the carbazole-modified acrylate polymer was dispersed in a water-ethylene glycol system, diluted 10 times, and a few drops were taken and placed on a 300-mesh copper grid and air-dried at room temperature to prepare a transmission electron microscope sample. Figure 6 shown, the morphology of the polymer after carbazole modification under complete carboxyl group neutralization (the carboxyl group neutralization ratio was 100%) was uniform and spherical, and the particle size (R) was about 20 nm.

[0046] Example 6

[0047] As Figure 7 shown, the neutralized carbazole-modified acrylate polymer with a concentration of 5 g / L was dispersed in a water-ethylene glycol system. This dispersion was used as an electrophoretic paint, with a conductive glass FTO as the anode and a platinum electrode as the cathode. The voltage was 30 V, and it was electrified at room temperature for 600 s. After the obtained film was air-dried at room temperature, gold spraying was carried out to prepare a scanning electron microscope sample. Figure 7 shown, the polymer particles in the deposited film were crosslinked and had certain mechanical properties.

Claims

1. A carbazole-modified acrylate polymer, characterized in that, The polymer structural formula is as follows: There is no special limitation on the ratio of m, n, and o, which can be adjusted as needed.

2. The carbazole-modified acrylate polymer according to claim 1, wherein m∶n∶o = (5 - 30)∶(1 - 15)∶(0.01 - 5).

3. A carbazole-modified acrylate polymer according to claim 1, characterized in that, In the polymer structural formula, the R1 substituent is a straight-chain alkyl group, such as -(CH2) n -CH3, where n = 0 - 10, corresponding to methyl when n = 0, or a branched-chain alkyl group with C4 - C12, or an alkyl chain containing a hydroxyl substituent, one or more of them; R2 and R3 are hydrogen atoms, or methyl groups; R4 is an alkyl chain, such as -(CH2) n -, n = 0 - 5, or an alkyl chain containing an ester group, such as -COO-(CH2) n -, n = 0 - 5, one or more of them.

4. A method for preparing a carbazole-modified acrylate polymer according to any one of claims 1 to 3, characterized in that, It includes the following steps: Using the free radical polymerization method, the solvent can be an organic solvent such as isopropyl alcohol, n-butanol, ethanol, acetone, N,N-dimethylformamide, etc., and the initiator is an azo compound. All monomers and the initiator are ultrasonically treated in an ice-water bath to be mixed evenly, and then heated for reaction. The reaction temperature is set to be about 5°C lower than the boiling point of the solvent used. After reacting for a period of time, a carbazole-modified acrylate polymer is obtained; The monomers include the following:

5. Use of a carbazole-modified acrylate polymer according to any one of claims 1 - 3 for an anti-corrosion coating.

6. The use according to claim 5, compounded with benzotriazole for an anti-corrosion coating; the mass ratio of benzotriazole to the polymer is (1 - 5)∶5.

7. A preparation method of an additive-containing anodic electrophoretic paint, characterized in that, It includes the following steps: First, use an organic base containing an amino group to neutralize the carboxyl group in a carbazole-modified acrylate polymer according to any one of claims 1 - 3 to form a carboxyl group-containing anionic polymer. The degree of neutralization can be adjusted according to actual needs. The degree of neutralization is defined as the ratio of the amount of substance of amino groups in the neutralizing base to the amount of substance of carboxyl groups in the polymer; Take out the neutralized carboxyl group-containing anionic polymer, disperse it evenly in a water-ethylene glycol system, and add benzotriazole for compounding to obtain an anodic electrophoretic paint containing additives; the mass ratio of benzotriazole to the polymer is (1 - 5)∶5; the mass percentage concentration of the carboxyl group-containing anionic polymer in the water-ethylene glycol system is 0.2 - 10 g / L, preferably 0.5 - 5 g / L.

8. The method according to claim 7, wherein The corresponding degree of neutralization: The molar percentage of neutralized carboxyl groups in the original total carboxyl groups is 50 - 100%; The volume ratio of water to ethylene glycol is preferably 2∶3; the organic base containing an amino group is selected from one of N,N-dimethylethanolamine and triethylamine.

9. A method for preparing a metal substrate protective film using the electrophoretic paint obtained by the method according to claim 7 or 8, characterized in that, Use the above anodic electrophoretic paint containing additives to deposit a protective film on the surface of a metal substrate. The anode is the metal substrate, and the cathode is a platinum sheet. Electrify at 30 V for 1 - 5 h, and a relatively dense film is deposited on the anode metal substrate.

10. The method according to claim 9, wherein the film is a corrosion-resistant film; the integrity of the film can be detected by fluorescence.

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