WO2022127745A1

WO2022127745A1 - Polyurethane modified graphene microsheet and preparation method therefor

Info

Publication number: WO2022127745A1
Application number: PCT/CN2021/137546
Authority: WO
Inventors: 冯增辉; 汪洋; 刘兰轩; 康岩松; 李冬冬; 秦卫华; 吴东恒
Original assignee: 武汉材料保护研究所有限公司
Priority date: 2020-12-14
Filing date: 2021-12-13
Publication date: 2022-06-23
Also published as: AU2021402785A1; CN112608436A

Abstract

Provided in the present disclosure are a polyurethane modified graphene microsheet and a preparation method therefor, the preparation method specifically comprising: adding graphene oxide and polyol into a three-neck flask according to a ratio, stirring and mixing same, and carrying out high-temperature vacuum dehydration at the same time; continuously mixing and stirring same after the high-temperature vacuum dehydration is finished, stopping heating, controlling the reaction temperature, cooling to room temperature, gradually adding isocyanate, monitoring the reaction temperature, adjusting the adding rate according to the reaction temperature, and controlling the reaction temperature to be maintained below T°C; and finally, after isocyanate is added and reacted for 10-30 min, controlling the reaction temperature within a range of 75-85°C by using oil bath heating, stirring and reacting for 1.5-3 h, and filtering and packaging by using a filter screen to complete the preparation of a polyurethane modified graphene microsheet. The polyurethane modified graphene microsheet prepared in the present disclosure is used in an epoxy resin coating material, and graphene may be uniformly oriented and distributed in a coating, thus greatly improving the corrosion resistance of the coating.

Description

A kind of polyurethane modified graphene microplate and preparation method thereof

CROSS-REFERENCE TO RELATED APPLICATIONS

This disclosure claims the priority of the Chinese patent application with the application number CN 202011476438.9 and the title of "a polyurethane-modified graphene microsheet and its preparation method" filed with the China Patent Office on December 14, 2020, the entire contents of which are passed References are incorporated in this disclosure.

technical field

The present disclosure belongs to the field of coatings, relates to an epoxy coating modification technology, and in particular relates to a polyurethane-modified graphene microchip and a preparation method thereof.

Background technique

With the increasingly strict environmental protection policies in my country, the application needs of environmentally friendly long-life protective coatings in marine engineering equipment, ships, petrochemicals, bridges and major equipment industries are increasingly urgent. The commonly used solvent anti-corrosion coatings will be gradually eliminated from the market, and the application of solvent-free coatings will become more and more extensive. Among them, solvent-free epoxy coatings are one of the most widely used varieties. Solvent-free epoxy coatings have the advantages of strong adhesion, good corrosion resistance and long service life. However, the coating viscosity is high, the mixing pot life is short, the low temperature curing speed is slow, the coating has the disadvantages of high brittleness, poor interlayer adhesion, and insignificant "labyrinth" shielding effect. Compared with the use requirements, there is a big gap. Graphene (Gr) is a sheet-like two-dimensional structure composed of carbon atoms, which has the characteristics of high strength, strong physical barrier and good thermal stability. The precipitation properties can significantly improve the flexibility, corrosion resistance and high and low temperature resistance of the coating, but due to its large surface polarity, easy agglomeration and stacking and other defects, the actual use effect of graphene microflakes in the coating is greatly reduced. , and because of its conductivity, the conductive channels formed by lap bonding in the closed coating further accelerate the electrochemical corrosion of the metal substrate. Therefore, the long-term dispersion stability of graphene and its compatibility with organic resins are improved by graphene. The key to the promotion and application of sexual coatings.

Invention patent with publication number CN110128943A "A kind of graphene high-efficiency anti-corrosion coating and preparation method and product thereof", the graphene high-efficiency anti-corrosion coating prepared from raw materials such as solvent-based epoxy resin, anti-rust pigment, organic solvent, curing agent, etc. , using the characteristics of graphene to enhance the long-term effect of anti-corrosion protection to a certain extent, but the preparation method uses more solvents and catalysts for dispersion reaction, and the environmental protection is not high.

SUMMARY OF THE INVENTION

The purpose of the present disclosure is to provide a polyurethane-modified graphene microplate and a preparation method thereof, which are prepared by processes such as dehydration, addition polymerization, and purification, using polyol, isocyanate and graphene oxide as raw materials. The polyurethane-modified graphene micro-sheets prepared in the present disclosure are used to modify epoxy resins, and the graphene oxide micro-sheets are modified by polyurethane prepolymers and the hydroxyl groups on the epoxy molecular chain are added and polymerized to form graphene block polymerization. It realizes the chemical bonding between the graphene microplates and the resin matrix, so that they are completely oriented in the resin matrix, forming a labyrinth effect, fully exerting the shielding performance of the graphene microplates, and greatly improving the corrosion protection of the coating. performance.

The purpose of this disclosure is achieved through the following technical solutions:

The present disclosure also provides a method for preparing a polyurethane-modified graphene microsheet, comprising the following steps:

Step (1) adding graphene oxide and polyol in the there-necked flask according to the proportioning, stirring and mixing, and simultaneously carrying out high temperature vacuum dehydration;

Step (2) continue mixing and stirring after the high-temperature vacuum dehydration finishes, stop heating, control the reaction temperature to be cooled to room temperature, gradually add isocyanate, monitor the reaction temperature, adjust the addition rate according to the reaction temperature, and control the reaction temperature to remain below ℃;

Step (3) After the isocyanate is added for 10 to 30 minutes, the reaction temperature is controlled within the range of 75 to 85° C. by heating with an oil bath, and the reaction is stirred for 1.5 to 3 hours. Preparation of graphene microflakes.

Preferably, the proportioning of described polyol, isocyanate and graphene oxide is as follows by mass:

Polyols 60～100

Isocyanate 80～150

Graphene oxide 1～10.

Preferably, in step (1), the specific method of high temperature vacuum dehydration is to use oil bath heating to control the temperature within the range of 105-120°C, and use a vacuum pump to perform vacuum dehydration for 1.5-3 hours.

Preferably, in step (3), the mesh number of the filter screen is 150-250.

Preferably, the polyol is any one or more of PTMG1000, PTMG650, PCDL1000, diethanolamine and triethanolamine.

Preferably, the isocyanate is HDI (1,6-hexamethylene diisocyanate), MDI (diphenylmethane diisocyanate), IPDI (isophorone diisocyanate), HMDI (4,4'-dicyclohexylmethane diisocyanate) Isocyanate), TDI (toluene diisocyanate), LDI (L-lysine diisocyanate) any one or more.

Preferably, the range of T in step (2) is 70-80°C.

The present disclosure also provides a polyurethane-modified graphene micro-sheet, which is prepared by any one of the preparation methods described above.

The present disclosure also provides a use of the polyurethane-modified graphene microsheets for the modification of solvent-free epoxy coatings. The polyurethane-modified graphene micro-sheets prepared by the present disclosure are used to modify the solvent-free epoxy coating, and the specific method is as follows:

Step (1) according to the formula ratio, adding the polyurethane modified graphene micro-sheets into the solvent-free epoxy resin, and stirring at 60°C～80°C for 20～60min to prepare the matrix resin of the coating;

Step (2) adding wetting and dispersing agent, anti-rust pigment and thickening agent to the matrix resin at one time in proportion, and grinding at room temperature with a sand mill.

Step (3) adding the defoaming agent in batches during the grinding process, and controlling the dosage not to exceed 5% of the total formula, grinding to a fineness of less than 50 μm, and using a filter screen to filter and encapsulate to obtain a coating base material;

Step (4) Before coating, the coating base material is stirred and aged for 30-40 minutes, and then mixed with the curing agent in the above proportion to obtain a long-lasting anti-corrosion graphene modified solvent-free epoxy coating that can be coated.

Preferably, each component of the formula ratio is as follows in terms of mass:

Preferably, the polyurethane-modified graphene micro-sheets are mainly prepared from polyols, isocyanates and graphene oxide through dehydration, addition polymerization and purification processes.

Preferably, the solvent-free epoxy resin is any of low molecular weight modified bisphenol A epoxy, low molecular weight modified bisphenol F epoxy, low molecular weight alicyclic epoxy, and low molecular weight phenolic modified epoxy resin One or more compound resins.

Preferably, the wetting and dispersing agent is a solvent-free associative polyurethane and/or a solvent-free acrylic dispersant.

Preferably, the antirust pigment is a compound of any one or more of zinc phosphate, aluminum tripolyphosphate, glass flakes, iron red, and zinc powder.

Preferably, the defoamer is a hydrophobic ion-containing silicone defoamer.

Preferably, the thickener is any one of organic soil, fumed silica, and polyamide thickeners.

Preferably, the curing agent is DETA (diethylenetriamine), TETA (triethylenetetramine), DEPA (triethylaminopropylamine), TEPA (tetraethylenepentamine), MDA (mantanediamine), IPDA ( Any one or more of isophorone diamine), DDS (diaminodiphenyl sulfone), and DDM (diaminodiphenylmethane).

Preferably, the filter screen used in step (3) is 150-250 mesh, and the most optimal is 200 mesh.

The present disclosure also provides a long-term anti-corrosion graphene modified solvent-free epoxy coating, which is characterized in that: it is prepared by any one of the above preparation methods.

The beneficial effects of the present disclosure are as follows:

In the present disclosure, the graphene is grafted onto the epoxy molecular chain by means of chemical grafting, and the graphene micro-sheets are limited and dispersed by chemical bonds, which solves the problem of easy agglomeration and stacking of the graphene micro-sheets, and realizes the graphene micro-sheets in the Long-term stable dispersion in coatings. In addition, the present disclosure utilizes the polyurethane structure to chemically graft the graphene oxide microplates onto the epoxy molecular chain, and then conduct ring-opening polymerization between the epoxy group and the amine group in the curing agent to form a dense three-dimensional network structure. The graphene micro-sheets are thoroughly spread out, and the directional arrangement of the graphene micro-sheets in the coating can be realized, so that the characteristics of graphene with ultra-high specific surface area, super-hydrophobicity and high shielding can be fully reflected, which is the coating material. The long-term anti-corrosion performance of the coating provides a favorable guarantee, and combined with traditional anti-rust pigments, the corrosion resistance of the coating can be further improved.

Description of drawings

FIG. 1 is a low-magnification fracture topography diagram of pure epoxy resin in an embodiment of the disclosure.

FIG. 2 is a high-magnification fracture topography diagram of pure epoxy resin in an embodiment of the disclosure.

3 is a low-magnification fracture morphology of a graphene-modified epoxy resin in an embodiment of the disclosure.

FIG. 4 is a high-magnification fracture morphology of graphene-modified epoxy resin in an embodiment of the disclosure.

Figure 5. Mechanical properties of modified and unmodified epoxy resins.

Figure 6 shows the macroscopic morphology of the graphene modified solvent-free epoxy coating in the salt spray test, in which Figure 6(a) is the original morphology of the coating before the salt spray test, and Figure 6(b) is the coating after the salt spray test. corrosion morphology.

Figure 7 is the macroscopic topography of the solvent-free epoxy coating in the salt spray test of the comparative example, in which Figure 7(a) is the original topography of the coating before the salt spray test, and Figure 7(b) is the coating after the salt spray test. Corrosion morphology.

Detailed ways

The embodiments of the present disclosure will be described in further detail below with reference to the accompanying drawings and examples. The following examples are intended to illustrate the present disclosure, but not to limit the scope of the present disclosure.

The preparation method of polyurethane-modified graphene microplates is as follows:

Example 1:

Step (1) add 1g of graphene oxide and 60g of polyol into the three-necked flask, stir and mix, use oil bath heating to control the temperature within the range of 105-120°C, and use a vacuum pump to carry out vacuum dehydration for 1.5-3h;

Step (2) continue mixing and stirring after the high-temperature vacuum dehydration finishes, stop heating, control the reaction temperature to be cooled to room temperature, gradually add 80g isocyanate, monitor the reaction temperature, adjust the addition rate according to the reaction temperature, and control the reaction temperature to remain below ℃;

Step (3) After 10-30 min of isocyanate addition, the reaction temperature is controlled within the range of 75-85° C. by heating in an oil bath, the reaction is stirred for 1.5-3 h, filtered and encapsulated with a 200-mesh filter screen, and the polyurethane-modified graphene microarray is completed. Tablet preparation.

Example 2:

Step (1) add 5g graphene oxide and 70g polyol into the three-necked flask, stir and mix, use oil bath heating to control the temperature within the range of 105-120°C, and use a vacuum pump to carry out vacuum dehydration for 1.5-3h;

Step (2) continue mixing and stirring after the high temperature vacuum dehydration finishes, stop heating, control the reaction temperature to be cooled to room temperature, gradually add 100g of isocyanate, monitor the reaction temperature, adjust the addition rate according to the reaction temperature, and control the reaction temperature to remain below ℃;

Step (3) After 10-30 min of isocyanate addition, the reaction temperature is controlled within the range of 75-85° C. by heating in an oil bath, the reaction is stirred for 1.5-3 h, and filtered and encapsulated with a 200-mesh filter screen to complete the polyurethane-modified graphene microarray. Tablet preparation.

Example 3:

Step (1) add 8g graphene oxide and 80g polyol into the three-necked flask, stir and mix, use oil bath heating to control the temperature within the range of 105-120°C, and use a vacuum pump to carry out vacuum dehydration for 1.5-3h;

Step (2) continue mixing and stirring after the high temperature vacuum dehydration finishes, stop heating, control the reaction temperature to be cooled to room temperature, gradually add 130g isocyanate, monitor the reaction temperature, adjust the addition rate according to the reaction temperature, and control the reaction temperature to remain below ℃;

Example 4:

Step (1) adding 10g graphene oxide and 100g polyol into a three-necked flask, stirring and mixing, using oil bath heating to control the temperature within the range of 105-120°C, and using a vacuum pump for vacuum dehydration for 1.5-3h;

Step (2) continue mixing and stirring after the high-temperature vacuum dehydration finishes, stop heating, control the reaction temperature to be cooled to room temperature, gradually add 140g isocyanate, monitor the reaction temperature, adjust the addition rate according to the reaction temperature, and control the reaction temperature to remain below ℃;

The above-mentioned polyurethane-modified graphene micro-sheets are used for the modification of solvent-free epoxy coatings and the examples are as follows:

Example 5: Add 1 g of polyurethane-modified graphene microchips to 20 g of solvent-free epoxy resin, and stir for 20 to 60 min at 60°C to 80°C to prepare the matrix resin of the coating;

Step (2) Add 1g of wetting and dispersing agent, 1g of antirust pigment, and 1g of thickener to the matrix resin at one time, and use a sand mill to grind at room temperature, control the rotational speed at 1000-2500r/min, and grind for 2-5h;

Step (3) in the grinding process, add 1 g of defoaming agent in batches, control the dosage not to exceed 5% of the total formula, grind to a fineness of less than 50 μm, use a 200-mesh filter screen to filter and encapsulate to obtain a coating base material;

Step (4) Before coating, the coating base material is stirred and aged for 30 to 40 minutes, and then mixed with 10 g of curing agent in the above proportion to obtain a long-lasting anti-corrosion graphene modified solvent-free epoxy coating that can be coated.

Example 6: adding 2g of polyurethane-modified graphene microchips to 25g of solvent-free epoxy resin, and stirring at 60°C to 80°C for 20 to 60 minutes to prepare the matrix resin of the coating;

Step (2) Add 2g wetting and dispersing agent, 1g antirust pigment and 2g thickener to the matrix resin at one time, and grind at room temperature with a sand mill, control the rotational speed at 1000～2500r/min, and grind for 2～5h;

Embodiment 7: adding 10g of polyurethane-modified graphene microchips to 25g of solvent-free epoxy resin, and stirring at 60°C to 80°C for 20 to 60 minutes to prepare the matrix resin of the coating;

Step (2) adding 3g of anti-rust pigment and 2g of thickener to the matrix resin at one time, grinding at room temperature with a sand mill, controlling the rotational speed at 1000-2500r/min, and grinding for 2-5h;

Step (3) in the grinding process, add 2 g of defoamer in batches, control the dosage not to exceed 5% of the total formula, grind to a fineness of less than 50 μm, and use a 200-mesh filter screen to filter and encapsulate to obtain a coating base material;

Example 8: adding 15g of polyurethane-modified graphene microflakes to 50g of solvent-free epoxy resin, and stirring at 60°C to 80°C for 20 to 60 minutes to prepare the matrix resin of the coating;

Step (2) adding 3g of anti-rust pigment and 3g of thickener to the matrix resin at one time, grinding at room temperature with a sand mill, controlling the rotational speed at 1000-2500r/min, and grinding for 2-5h;

Step (3) in the grinding process, add 4 g of defoamer in batches, control the dosage not to exceed 5% of the total formula, grind to a fineness of less than 50 μm, and use a 200-mesh filter screen to filter and encapsulate to obtain a coating base material;

Example 9: adding 20g of polyurethane-modified graphene microchips to 70g of solvent-free epoxy resin, and stirring at 60°C to 80°C for 20 to 60 minutes to prepare the matrix resin of the coating;

Step (2) adding 4g of anti-rust pigment and 5g of thickener into the matrix resin at one time, and grinding at room temperature with a sand mill, controlling the rotational speed at 1000-2500r/min, and grinding for 2-5h;

Electron microscope scanning was performed on the polyurethane-modified graphene microplatelet modified solvent-free epoxy coating and the pure solvent-free epoxy coating prepared in Example 5 of the present disclosure, and the obtained structures are shown in Figures 1 to 4, from Figure 1 to Figure 1 4, it can be seen that the fracture morphology of pure epoxy resin is smooth and flat, and there are no ductile failure characteristics such as diffusion cracks and steps, which belong to obvious brittle fracture. The fracture morphology of the post-cured resin shows a large number of structural features such as vortices, ditches, and steps, indicating that the material is resisted in different directions when it is damaged by force, and the direction of stress failure occurs irregularly, showing obvious toughness. It is due to the large specific surface area and excellent mechanical properties of the directionally-arranged graphene micro-sheet structure, which plays an obvious reinforcing role in the epoxy resin, improves the toughness of the epoxy resin, and improves the brittleness of the epoxy resin.

With reference to the standard GBT 228.1-2010 "tensile test of metallic materials - Part 1: Test method at room temperature" and the standard GB/T 232-2010 "Bending test method of metallic materials", the pure epoxy resin material and the graphene prepared in Example 5 were carried out The tensile and flexural properties of the modified epoxy resin material are tested, and the results are shown in Figure 5. Compared with the pure epoxy resin, the tensile strength and flexural strength of the epoxy resin added with the polyurethane-modified graphene microsheets are higher. high, the comprehensive mechanical properties of the material are better.

Referring to the standard GB/T 10125-2012 "Salt Spray Test for Artificial Atmosphere Corrosion Test", the graphene-modified solvent-free epoxy coating prepared in Example 5 and the ring of the polyurethane-modified graphene microplatelets were coated on the Q235 steel plate. Different coating samples made of oxygen coatings were tested for salt spray resistance. The macroscopic morphology before and after 5000h in a neutral salt spray atmosphere is shown in the figure. It can be seen that the solvent-free polyurethane-modified graphene microsheets are added. The corrosion diffusion of the epoxy coating is obviously better than that of the solvent-free epoxy coating without modified graphene microchips. The evenly distributed graphene microflakes have good shielding properties, which can significantly improve the corrosion resistance of the coating.

The above embodiments are only used to illustrate the present disclosure, but not to limit the present disclosure. Although the present disclosure has been described in detail with reference to the embodiments, those of ordinary skill in the art should understand that various combinations, modifications or equivalent substitutions to the technical solutions of the present disclosure do not depart from the spirit and scope of the technical solutions of the present disclosure, and should cover are within the scope of the claims of the present disclosure.

Claims

A preparation method of polyurethane-modified graphene microchips, is characterized in that, comprises the following steps:

Step (1) adding graphene oxide and polyol in the there-necked flask according to the proportioning, stirring and mixing, and simultaneously carrying out high temperature vacuum dehydration;

Step (2) continue mixing and stirring after the high-temperature vacuum dehydration finishes, stop heating, control the reaction temperature to be cooled to room temperature, gradually add isocyanate, monitor the reaction temperature, adjust the addition rate according to the reaction temperature, and control the reaction temperature to remain below ℃;

Step (3) After 10-30 min of isocyanate addition, the reaction temperature is controlled within the range of 75-85° C. by heating in an oil bath, and the reaction is stirred for 1.5-3 h, and then filtered and encapsulated by a filter screen to complete the preparation of polyurethane-modified graphene microchips. .
The preparation method of polyurethane-modified graphene microplates as claimed in claim 1, is characterized in that: the proportioning of described polyol, isocyanate and graphene oxide is as follows by mass:

Polyols 60～100

Isocyanate 80～150

Graphene oxide 1～10.
The preparation method of polyurethane-modified graphene microchips as claimed in claim 1, characterized in that: in step (1), the specific method for high-temperature vacuum dehydration is to use oil bath heating to control the temperature within the range of 105 to 120 °C, and to use a vacuum pump to control the temperature. Carry out vacuum dehydration for 1.5-3h.
The preparation method of the polyurethane-modified graphene micro-sheet according to claim 1, characterized in that: in step (3), the mesh number of the filter screen is 150-250.
The method for preparing polyurethane-modified graphene micro-sheets according to claim 1, wherein the polyol is any one or more of PTMG1000, PTMG650, PCDL1000, diethanolamine, and triethanolamine.
The method for preparing polyurethane-modified graphene micro-sheets according to claim 1, wherein the isocyanate is any one or more of HDI, MDI, IPDI, HMDI, TDI, and LDI.
The method for preparing polyurethane-modified graphene microplates according to claim 1, wherein the range of T described in step (2) is 70-80°C.
A polyurethane-modified graphene microplate is characterized in that: it is prepared by the preparation method described in any one of claims 1-7.