GRAPHENE-SILANE TREATING AGENT AND PREPARATION METHOD THEREFOR AND APPLICATION THEREOF

Description

FIELD OF THE INVENTION

[0001] The present invention relates to the technical field of metal surface treatment, more particularly, to a graphene-silane treating agent and a preparation method therefore and application thereof.

BACKGROUND OF THE INVENTION

[0002] In the metal surface pretreatment industry, traditional phosphating treatment has an application history of nearly one hundred years, and the mature process thereof is generally: sandblasting → cleaning → pre-degreasing → degreasing → washing with water → washing with water → expression→ phosphating → washing with water → washing with water. With the gradual implementation of national regulations about energy conservation and emission reduction and the background of national limitation on carbon emission, the phosphating treatment needs to consume a lot of energy, and the phosphating solution contains phosphorus and heavy metal elements such as zinc, manganese, and nickel, which has been conventionally eliminated. The phosphating solution has been replaced by new silane surface treatment agents, such as phosphorus-free nano-ceramification agents or silicon-zirconium composite treatment agents containing environmentally-friendly materials such as zirconium, titanium, silane coupling agents, etc. Although these three types of agents are energy-saving and environmentally friendly, their performance is far from being comparable to the phosphate treatment in terms of current application situations. For example, it can only be applied to a cold-rolled plate, but cannot be applied to a sand-blasting plate, because the self-drying speed of the sand-blasting plate is slow, and the bumpy surface thereof tends to store water and acid; therefore, after the sand-blasting plate is treated by the silylation, the water-washed self-drying and anti-rusting phenomenon thereof are relatively severe, and the corrosion resistance of the silane film, the ceramic film, and the silicon-zirconium composite film are greatly reduced relative to that of the phosphide film.

[0003] Chinese patent CN 201710588262.8A discloses a nano-ceramic silane composite film conversion agent containing graphene oxide, which consists of 10-50 parts of fluorozirconic acid, 1-20 parts of nitric acid, 1-5 parts of silica sol, 1-5 parts of complexing agent, 0.1-3 parts of a silane coupling agent, 0.1-1 parts of graphene oxide and water to make up 100 parts. According to the disclosure, silane and silica sol are added into a zirconium salt system for modification to prepare a conversion agent having homogeneous phase stability; an amorphous composite film is obtained using the synergistic treatment of the zirconium salt silane; a gap of the film can be supplemented by graphene oxide so that the film is more uniform and dense; and a paint film of the disclosure is also improved to a great extent in a neutral salt fog resistance test. In the patent, graphene oxide can only make up the gap of the film and is not a main constituent part of the amorphous composite film. The amorphous composite film obtained in the disclosure is improved to a great extent in the neutral salt fog resistance test after mating with the paint film; however, for the amorphous composite film, the corrosion resistance thereof is poor, particularly when the the water-washed self-drying is mated with the sand-blasting plate, reduce is severe within a short time after the water-washed self-drying.

[0004] To solve the current defects in the metal surface pretreatment industry, it is necessary to develop a graphene-silane treating agent with better corrosion resistance.

SUMMARY OF THE INVENTION

[0005] The object of the present invention is to overcome the defect in the prior art, to provide a graphene-silane treating agent and a preparation method therefore and application thereof, the graphene-silane treating agent is not only applicable to cold-rolled plates, galvanized plates, magnesium aluminum plates, etc., but also applicable to sand-blasting plates, to form a graphene-silane film having better the corrosion resistance than the zinc phosphide film, and is a chemical agent for pre-treating metal surface.

[0006] The schemes of the present invention are as follows:
A graphene-silane treating agent is prepared from the following components in percentage by weight: 0.8-1.2% of a graphene oxide dispersion, 8.3-10.3% of modified nano silicon dioxide, 2.1-3.1% of trimethoxy(3,3,3-trifluoropropyl)silane 0.6-0.8% of dimethoxy-methyl(3,3,3-trifluoropropyl)silane, 3.0-5.0% of fluorozirconic acid, 1.0-2.0% of lactic acid, 2.0-3.0% of ammonium citrate, and the balance of water.

[0007] In the graphene oxide dispersion, the sheet diameter of the graphene oxide is 50-200 nm, the concentration of the graphene oxide dispersion is 0.2-1 mg/ml, and the solvent is water. Preferably, the graphene oxide dispersion is XF020 manufactured by Jiangsu Xianfeng Nano Material Technology Co., Ltd.

[0008] The preparation method of the modified nano-silica is as follows:

(1) adding 0.5-1.0 parts by weight of hydrophobic gas-phase nano-silica into 15-25 parts by weight of toluene, and dispersing the same into a uniform suspension;

(2) then adding 0.350-0.370 parts by weight of γ -(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) to the uniform suspension, mixing by ultrasonic for 5-10min to obtain a reaction solution, which reacts in a thermostatic bath at 80-95° C for 5-7h, the reaction solution is centrifuged at normal temperature for 10000-15000 r/min to obtain the modified nano-silicon.

[0009] Preferably, the disperse conditions in step (1) are ultrasonic dispersion with an ultrasonic cleaner at normal temperature for 20-40min.

[0010] Preferably, the purity of the hydrophobic gas-phase nano-silica in step (1) is 99.5-99.9%, the specific surface area (BET) thereof is 100-120 m2/g, and the particle size thereof is 7-40 nm.

[0011] Preferably, the reaction solution in step (2) is ultrasonically centrifuged for 5-7 times, and vacuum-dried for 5 to 10 h to obtain the white powder, that is the modified nano-silica.

[0012] If the amount of the γ-(2,3-epoxypropoxy)propyltrimethoxysilane used in step (2) is too small, the modification of nano-silica is not complete; If the amount thereof is too large, the modified nano-silica will not be stable, and a white floc is formed to settle, which affects the surface treatment effect of the sand-blasting plates.

[0013] If the γ-(2,3-epoxypropoxy)propyltrimethoxysilane used in step (2) is replaced with trimethoxy(3,3,3-trifluoropropyl)silane or dimethoxy-methyl(3,3,3-trifluoropropyl)silane, the modified nano-silica is prone to condensation and sedimentation, thereby affecting the surface treatment effect of the sand-blasting plates.

[0014] Preferably, the trimethoxy(3,3,3-trifluoropropyl)silane is SCA-F3C3M produced by Nanjing Ningdong Material Technology Co., Ltd.

[0015] Preferably, the dimethoxy-methyl(3,3,3-trifluoropropyl)silane is SCA-F3C3T produced by Nanjing Ningdong Material Technology Co., Ltd.

[0016] The preparation method of the graphene-silane treating agent is as follows: adding the water into a reactive kettle, then adding the fluorozirconic acid, the lactic acid, the ammonium citrate, trimethoxy(3,3,3-trifluoropropyl)silane and the dimethoxy-methyl(3,3,3-trifluoropropyl)silane in sequence; after stirring for 7 to 10 hours, adding the graphene oxide dispersion and the modified nano-silica, and stirring for 12 to 15 hours to obtain the graphene-silane treating agent.

[0017] The method for using the graphene-silane treating agent is as follows: taking one 1000 ml beaker, adding 900-970 ml water and 30-40 g the graphene-silane treating agent into the beaker to obtain the graphene-silane treating liquid, testing the pH value of the graphene-silane treating liquid at 2.5-3.5, if the pH value is lower than 2.5, adding sodium carbonate to adjust the pH value at 2.5-3.5; if the pH value is greater than 3.5, adding the graphene-silane treating agent to adjust the pH value to 2.5-3.5.

[0018] The principle of the graphene-silane treating agent is as follows: when the pH value of the the graphene-silane treating liquid is 2.5-3.5, a polymerization reaction occurs among the graphene oxide and the trimethoxy(3,3,3-trifluoropropyl)silane, the dimethoxy-methyl(3,3,3-trifluoropropyl)silane, the modified nano-silica and the lactic acid to form a graphene-silane treating film with multi-layer cross-linked meshed structure. The modified nano-silica is a main agent for forming film and is a film framework; and the trimethoxy(3,3,3-trifluoropropyl)silane and the dimethoxy-methyl(3,3,3-trifluoropropyl)silane have complementarity in the spatial composition of the film, reducing the porosity of a film, and the amount of trimethoxy(3,3,3-trifluoropropyl)silane used is greater than that of the dimethoxy-methyl(3,3,3-trifluoropropyl)silane; if the amount of dimethoxy-methyl(3,3,3-trifluoropropyl)silane is greater than that of trimethoxy(3,3,3-trifluoropropyl)silane, it will result that the porosity of the graphene-silane treatment film is increased. When the blast test pieces are immersed in the graphene-silane treating liquid, the pH value at the metal interface rises, and the graphene-silane treating film with a multi-layer cross-linked mesh-like structure is deposited on the metal surface to form a graphene-silane film. The fluorozirconic acid provides an acidic environment and a zirconium complex formed by hydrolysis is filled in the pores of the graphene-silane film; the lactic acid also participates in the formation of the graphene-silane film while providing an acidic environment. The ammonium citrate complexes iron or ferrous ions so as to prevent uneven film caused by interference of metal impurity ions when the graphene-silane film is deposited.

[0019] The present invention further provides the application of the graphene-silane treating agent in treating the sand-blasting plates.

[0020] The beneficial effects of the present invention are as follows: the graphene-silane treating agent is not only applicable to cold rolled plates, galvanized sheets, magnesium-aluminum plates, etc., but also applicable to sand blasting steel plates, and the formed graphene-silane film has better corrosion resistance than a zinc phosphide film and is a chemical agent for pre-treatment of a metal surface. After the sand blasting steel plates with a rust removal rating of Sa2.5 are sprayed with the graphene-silane treating agent, a graphene-silane film is formed on the surface of the grit-blasted plate. The sand-blasted steel plate is washed and self-dried and left for three months without rusting.

EMBODIMENTS

[0021] Preparing a modified nano-silica A as follows:

(1) adding 0.5 parts by weight of hydrophobic gas-phase nano-silica into 15 parts by weight of toluene, and dispersing for 30min to obtain a uniform suspension ;

(2) adding 0.350 parts by weight of γ -(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) to the uniform suspension, mixing by ultrasonic for 7min to obtain a reaction solution, which reacts in a thermostatic bath at 85° C for 6h, the reaction solution is centrifuged at normal temperature for 12000r/min to obtain the modified nano-silicon A.

[0022] The purity of the hydrophobic gas-phase nano-silica in step (1) is 99.5-99.9%, the specific surface area (BET) thereof is 100-120 m2/g, and the particle size thereof is 7-40 nm.

[0023] The reaction solution in step (2) is ultrasonically centrifuged 7 times and vacuum-dried for 6 h to obtain the white powder, that is the modified nano-silica.

[0024] Preparing a modified nano-silica B as follows:

(1) adding 0.1 parts by weight of hydrophobic gas-phase nano-silica into 25 parts by weight of toluene, and dispersing for 30min to obtain a uniform suspension;

(2) then adding 0.370 parts by weight of γ -(2,3-epoxypropoxy)propyltrimethoxysilane (KH-560) to the uniform suspension, mixing by ultrasonic for 7 min to obtain a reaction solution, which reacts in a thermostatic bath at 90° C for 7h, the reaction solution is centrifuged at normal temperature for 15000 r/min to obtain modified nano-silicon B.

[0025] The purity of the hydrophobic gas-phase nano-silica in step (1) is 99.5-99.9%, the specific surface area (BET) thereof is 100-120 m2/g, and the particle size thereof is 7-40 nm.

[0026] The reaction solution in step (2) is ultrasonically centrifuged 7 times and vacuum-dried for 6 h to obtain the white powder, that is the modified nano-silica.

[0027] The examples and comparative examples of the present invention are shown in Table 1 (percentage content), wherein the comparative example 1 uses a corresponding unmodified hydrophobic fumed nano-silica, and the others are the same as those in example 4; in the comparative example 2, the amount of the trimethoxy(3,3,3-trifluoropropyl)silane is 3.9%, which is the sum of the amount of the trimethoxy(3,3,3-trifluoropropyl)silane and the amount of the dimethoxy-methyl(3,3,3-trifluoropropyl)silane in example 4, and does not contain dimethoxy-methyl(3,3,3-trifluoropropyl)silane; in the comparative example 3, the amount of the dimethoxy-methyl(3,3,3-trifluoropropyl)silane used is 3.9%, which is the sum of the amount of the trimethoxy(3,3,3-trifluoropropyl)silane used and the amount of the dimethoxy-methyl(3,3,3-trifluoropropyl)silane used in example 4, and does not contain the trimethoxy(3,3,3-trifluoropropyl)silane; in the comparative Example 4, the lactic acid is replaced with the same amount of the nitric acid, the others are the same as those in example 2.

Table 1

	example 1	example 2	exampl e3	example 4	comparative example 1	comparative example 2	comparative example 3	comparative example 4
graphene oxide dispersion	0.8	0.9	1	1.2	1.2	1.2	1.2	0.9
modified nano-silica A	9.1	10.1	-	-	-	-	-	10.1
modified nano-silica B	-	-	9.1	10.1	10.1 (nonmodifie d )	10.1	10.1	-
trimethoxy(3,3,3-tr ifluoropropyl)silan e	2.3	2.6	2.9	3.1	3.1	3.9	0	2.6
dimethoxy-methyl (3,3,3-trifluoropro pyl)silane	0.6	0.7	0.7	0.8	0.8	0	3.9	0.7
fluorozirconic acid	3.3	3.9	4.3	4.9	4.9	4.9	4.9	3.9
lactic acid	1.2	1.5	1.7	1.9	1.9	1.9	1.9	1.5(nitric acid)
ammonium citrate	2.1	2.4	2.7	2.9	2.9	2.9	2.9	2.4
water	balance	balance	balan ce	balance	balance	balance	balance	balance

[0028] The preparation method of the graphene-silane treating agent is as follows:
adding the water into a reactive kettle, then the adding fluorozirconic acid, the lactic acid, the ammonium citrate, trimethoxy(3,3,3-trifluoropropyl)silane and the dimethoxy-methyl(3,3,3-trifluoropropyl)silane in sequence; after stirring for 8 hours, adding the graphene oxide dispersion and the modified nano-silica, and stirring for 12 to 15 hours to obtain the graphene-silane treating agent.

[0029] The method for using the graphene-silane treating agent is as follows:
take one 1000 ml beaker, adding 970 ml water and 30 g graphene-silane treating agent into the beaker to obtain a graphene-silane treating liquid, testing the pH value of the graphene-silane treating liquid at 2.5-3.5, if the pH value is lower than 2.5, add sodium carbonate to adjust the pH value at 2.5-3.5; if the pH value is greater than 3.5, add the graphene-silane treating agent to adjust the pH value to 2.5-3.5. Put the sand blasting steel plates into the above graphene-silane treating agent, take them out after 5 minutes, clean them with water, and dry them, the graphene-silane films are formed on the surface of the sand blasting steel plates.

[0030] The performances of the graphene-silane film formed on the metal surface by the graphene-silane treating agent are shown in Tables 2-3, and the data in Table 2 are the test results after the graphene-silane film is formed on the surface of the grit-blasted steel plate with rust removal rating of Sa2.5.

Table 2

	example 1	example 2	example 3	example 4	comparative example 1	comparative example 2	comparative example 3	comparative example 4
appearance	Grey black film, uniform and dense	Grey black film, uniform and dense	Grey black film, uniform and dense	Grey black film, uniform and dense	Colorless film, uneven and non dense	Grey black film, uniform and dense	Grey black film, uniform and dense	Grey black film,few areas without film
thickness	343nm	453nm	491nm	531nm	30nm	43nm	126nm	16nm
weight	0.6g/m2	0.9g/m2	1.01g/m2	1.2g/m2	0.05g/m2	0.08g/m2	0.25g/m2	0.03g/m2
Neutral Salt Spray test	12h	12h	12h	12h	0.5h	2h	3h	15min
Sodium chloride immersion test	20h	20h	20h	20h	0.5h	2h	3h	10min
impact test	100kg· cm	100kg· cm	100kg· cm	100kg· cm	20kg· cm	30kg· cm	20kg· cm	10kg· cm
Bending test	3mm column, without damage	3mm column, without damage	3mm column, without damage	3mm column ,without damage	3mm column .cracking	3mm column, cracking	3mm column, cracking	3mm column, cracking
copper sulphate dropping experiment	8min23s	8min36s	8min45s	8min57s	15s	1min2s	1 min3 3 s	3s
high temperature resistance test	300°C, 4h, ΔE=2.1	300°C, 4h, ΔE=2.3	300°C, 4h, ΔE=2.4	300°C, 4h, ΔE=2.5	300°C, 4h, ΔE=5.6	300°C, 4h, ΔE=4.9	300°C, 4h, ΔE=5.3	300°C, 4h, ΔE-10.6
corrosion results after 3 months of storage	No visible corrosion	No visible corrosion	No visible corrosion	No visible corrosion	Severe yellow corrosion, with corrosion spreading 2mm towards the interior of the substrate	Uniform yellow corrosion	niform yellow corrosion	Severe yellow corrosion, with corrosion spreading 5mm towards the interior of the

Table 3

Serial Number	subject	performance parameter	Test methord
1	appearance	Grey black film, uniform and dense	visualization
2	thickness	300-600nm	film thickness gauge
3	weight	0.5-1.5g/m2	XRF analytical method
4	Neutral Salt Spray test	12h	ASTMB117-2011
5	Sodium chloride immersion test	20h	Immerse the test piece in a 5% concentration sodium chloride solution
6	impact test	≥100kg· cm	Impact Tester
7	Bending test	≤3 mm	Bending test
8	copper sulphate dropping experiment	≥8min	Copper sulfate test solution drops onto the surface of the test piece until red corrosion marks appear around the droplets
9	High temperature resistance test	300°C,4h, ΔE≤3.0	Measure the E-value of the film before and after baking at 300C for 4 hours using a spectrophotometer and calculate
10	Corrosion results after 3 months of storage	No corrosion	put outdoor, visualization

Claims

1. A graphene-silane treating agent, comprising components in percentage by weight:

0.8-1.2% of graphene oxide dispersion;

8.3-10.3% of modified nano silicon dioxide;

2.1-3.1% of trimethoxy(3,3,3-trifluoropropyl)silane;

0.6-0.8% of dimethoxy-methyl(3,3,3-trifluoropropyl)silane;

3.0-5.0% of fluorozirconic acid;

1.0-2.0% of lactic acid;

2.0-3.0% of ammonium citrate; and,

a balance of water.

2. The graphene-silane treating agent according to claim 1, wherein in said graphene oxide dispersion, a sheet diameter of said graphene oxide is 50-200 nm, a concentration of said graphene oxide dispersion is 0.2-1 mg/ml, and a solvent is water.

3. The graphene-silane treating agent according to claim 1, wherein a preparation method of said modified nano-silica as follows:

(1) adding 0.5-1.0 parts by weight of hydrophobic gas-phase nano-silica into 15-25 parts by weight of toluene, and dispersing for 30min to obtain a uniform suspension;

(2) adding 0.350-0.370 parts by weight of γ -(2,3-epoxypropoxy)propyltrimethoxysilane to said uniform suspension, mixing by ultrasonic for 5-10min to obtain a reaction solution, which reacts in a thermostatic bath at 80-95 °C for 5-7h, said reaction solution is centrifuged at normal temperature for 10000-15000 r/min to obtain modified nano-silicon.

4. The graphene-silane treating agent according to claim 3, wherein a specific surface area said hydrophobic gas-phase nano-silica in step (1) is 100-120 m2/g, and the particle size thereof is 7-40 nm.

5. The graphene-silane treating agent according to claim 3, wherein a disperse conditions in step (1) are ultrasonic dispersion with a ultrasonic cleaner at normal temperature for 20-40min;

6. The graphene-silane treating agent according to claim 3, wherein said reaction solution in step (2) is ultrasonically centrifuged for 5-7 times, and vacuum-dried for 5-10 h to obtain said modified nano-silica.

7. The graphene-silane treating agent according to claim 1, further comprising a components in percentage by weight:

1.2% of said graphene oxide dispersion;

10.1% of said modified nano silicon dioxide;

3.1% of said trimethoxy(3,3,3-trifluoropropyl)silane;

0.8% of said dimethoxy-methyl(3,3,3-trifluoropropyl)silane;

4.9% of said fluorozirconic acid;

1.9% of said lactic acid, 2.9% of said ammonium citrate, and

a balance of said water.

8. The preparation method of said graphene-silane treating agent according to claim 1, comprising steps as follows:

(1) firstly adding said water into a reactive kettle, then adding said fluorozirconic acid, said lactic acid, said ammonium citrate, said trimethoxy(3,3,3-trifluoropropyl)silane, and said dimethoxy-methyl(3,3,3-trifluoropropyl)silane in sequence;

(2) stirring for 7-10 hours, adding said graphene oxide dispersion and said modified nano-silica, and stirring for 12 to 15 hours to obtain said graphene-silane treating agent.

9. The application of said graphene-silane treating agent according to claim 1 used on sand blasting steel plate.