阅读说明：本技术 一种电镀锌钢带用无铬钝化剂的制备方法 (Preparation method of chromium-free passivator for electro-galvanized steel strip ) 是由 黄勇 陆飚 罗晓锋 郭文勇 于 2020-12-25 设计创作，主要内容包括：本发明涉及金属表面处理领域,具体公开了一种电镀锌钢带用无铬钝化剂的制备方法。本发明的电镀锌钢带用无铬钝化剂以改性聚四氟乙烯作为有机膜层,不需另外大量加入其它蜡乳,钝化剂稳定性较好。本发明使用改性聚四氟乙烯乳液作为无铬钝化剂中的有机组分,相对于一般的有机树脂,改性聚四氟乙烯乳液烘干成膜后,表面疏水疏油,可以阻止空气中的氧气等进一步的侵蚀,同时改性聚四氟乙烯膜层可赋予电镀锌钢带表面优异的润滑性(Ud在0.05～0.16之间)。(The invention relates to the field of metal surface treatment, and particularly discloses a preparation method of a chromium-free passivator for an electro-galvanized steel strip. The chromium-free passivator for the electro-galvanized steel strip takes the modified polytetrafluoroethylene as the organic film layer, and does not need to add other wax emulsion in a large amount, so that the passivator has good stability. Compared with common organic resin, the surface of the modified polytetrafluoroethylene emulsion dried to form a film is hydrophobic and oleophobic, so that oxygen in the air and the like can be prevented from further erosion, and meanwhile, the surface of the electrogalvanized steel strip can be endowed with excellent lubricity (Ud is between 0.05 and 0.16) by the modified polytetrafluoroethylene film.)

1. The preparation method of the chromium-free passivator for the electro-galvanized steel strip is characterized by comprising the following steps of:

10-50 parts by mass of modified polytetrafluoroethylene emulsion, 2-10 parts by mass of phosphate, 0.5-5 parts by mass of zirconium salt, 0.5-5 parts by mass of molybdate, 5-20 parts by mass of silicate and 50-150 parts by mass of deionized water;

the preparation method of the modified polytetrafluoroethylene emulsion comprises the following steps:

step 1, adding 0.1-1 part by mass of persulfate and 10-20 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a persulfate solution;

step 2, adding 3-6 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 0.5-2 parts by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 0.3-2 parts by mass of ammonium perfluorooctanoate and 50-80 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the persulfate solution and the solution in the reaction kettle are stirred and mixed, the reaction kettle is vacuumized, and tetrafluoroethylene gas is introduced until the pressure in the reaction kettle is 0.3-3 MPa;

step 5, starting stirring in the reaction kettle, heating to 40-60 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 4.5-7.5 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2-3 h, adding one half of the persulfate solution remained in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle, controlling the dropwise adding time to be 30-60 min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 30-50 parts by mass, adding the residual persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 2-3 hours;

step 7, adding 0.5-2 parts by mass of OP-10 and 0.5-2 parts by mass of AEO-9 into the reaction kettle, stirring for 20-40 min, and heating the reaction kettle until the liquid begins to boil until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; and cooling the reaction kettle to room temperature to obtain the modified polytetrafluoroethylene emulsion.

2. The preparation method according to claim 1, wherein the chromium-free passivator is prepared from the following raw materials: 20-40 parts of modified polytetrafluoroethylene emulsion, 3-6 parts of phosphate, 0.5-5 parts of zirconium salt, 0.5-5 parts of molybdate, 8-15 parts of silicate and 65-130 parts of deionized water.

3. The production method according to claim 1 or 2, wherein the phosphate is one or more of zinc phosphate, zinc dihydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate, and sodium dihydrogen phosphate.

4. The method according to claim 1 or 2, wherein the zirconium salt is one or more of zirconium acetate, zirconium nitrate and ammonium zirconium carbonate.

5. The method according to claim 1 or 2, wherein the molybdate is one or more of ammonium molybdate, sodium molybdate and potassium molybdate.

6. The method according to claim 1 or 2, wherein the silicate is one or more of sodium silicate, potassium silicate, and magnesium silicate.

7. The production method according to claim 1 or 2, wherein the persulfate in the step 1 is one or more of potassium persulfate, ammonium persulfate and sodium persulfate.

Technical Field

The invention relates to the field of metal surface treatment, in particular to a preparation method of a chromium-free passivator for an electro-galvanized steel strip.

Background

The electrogalvanized steel strip is a narrow and long steel strip applied to goods bundling, and is widely applied to industries such as steel, aluminum, chemical fiber, cotton spinning, tobacco, paper industry, metal can and the like, when the electrogalvanized steel strip which is not subjected to passivation treatment is used, the surface of the steel strip can be corroded by oxygen, water, carbon dioxide and the like in the air to generate white rust, the appearance and the service life of the steel strip are influenced, and the traditionally used passivator contains hexavalent chromium, is harmful to a human body and does not meet the requirement of environmental protection. In addition, when the steel belt is used for binding goods, the steel belt with low surface lubricity and the goods can generate larger friction to abrade the surface of the steel belt and damage a passivation layer or even an electro-galvanized layer on the surface of the steel belt, so that the corrosion on the surface of the steel belt is caused, at present, in order to meet the use requirement of the electro-galvanized steel belt, a trivalent chromium passivator is used for passivating the steel belt, then a lubricant is coated on the surface of the steel belt, a Labthink MXD-02 friction coefficient instrument is used for testing the dynamic friction coefficient Ud of the passivated steel belt according to GB/T10006 plus 1988, and when the dynamic friction coefficient Ud is between 0.05 and 0.16, the lubricity can meet the actual requirement.

A chromium-free passivator for a common galvanized steel plate replaces a traditional hexavalent chromium passivator by using a chromium-free inorganic system or organic-inorganic composite system passivator, but the friction coefficient of a passive film on the surface of the passive plate prepared by using the passivators is in a certain range, the dynamic friction coefficient Ud of the passive plate is tested by using a Labthink MXD-02 friction coefficient instrument according to GB/T10006-.

The patent application CN105316668A discloses an aqueous metal surface treatment composition which can be used for passivation treatment of the surface of galvanized steel sheet, but the passivation film has high friction coefficient and poor lubricity, and is difficult to meet the use requirement when packing steel strip bundle goods.

In the patent application of CN102002299A, a fingerprint resistant paint and a preparation method thereof are disclosed, the paint has a certain passivation effect on the surface of electrogalvanizing, wax slurry mixed by polyethylene and polytetrafluoroethylene according to a certain proportion is added into the paint, and a passivation film has a certain lubricity, but because of the subsequent requirement of coating adhesion, the dosage of the wax slurry in the paint cannot be too much, otherwise, the adhesion of the passivation film and finish paint is poor during coating. When the coating is used for the electrogalvanizing packing steel belt, the lubricity of the passive film is still difficult to meet the use requirement, the corrosion resistance of the passive film is reduced by continuously increasing the dosage of the wax slurry, and the phenomenon of wax slurry floating and layering can occur after the coating added with excessive wax slurry is placed for a period of time.

At present, a lot of chromium-free passivators are used for galvanized steel sheets in the market, the steel sheets are mainly used in the fields of household appliances and buildings, the requirements of the fields of household appliances and buildings on the lubricating property of a passivated sheet for a packed steel strip are not high, when the chromium-free passivators are used on the packed steel strip, the lubricating property is insufficient, and the requirements of practical application are difficult to meet, and particularly, the chromium-free passivators for the electrogalvanized steel strip are difficult to see, so that the chromium-free passivators for the electrogalvanized steel strip need to be developed.

Disclosure of Invention

Aiming at the defects of the existing passivator product, the invention aims to provide a preparation method of a chromium-free passivator for an electrogalvanized steel strip.

The technical scheme of the invention is as follows:

the preparation method of the chromium-free passivator for the electro-galvanized steel strip comprises the following steps: 10-50 parts by mass of modified polytetrafluoroethylene emulsion, 2-10 parts by mass of phosphate, 0.5-5 parts by mass of zirconium salt, 0.5-5 parts by mass of molybdate, 5-20 parts by mass of silicate and 50-150 parts by mass of deionized water;

further, the chromium-free passivator is prepared from the following raw materials: 20-40 parts by mass of modified polytetrafluoroethylene emulsion, 3-6 parts by mass of phosphate, 0.5-5 parts by mass of zirconium salt, 0.5-5 parts by mass of molybdate, 8-15 parts by mass of silicate and 65-130 parts by mass of deionized water;

further, the preparation method of the modified polytetrafluoroethylene emulsion comprises the following steps:

step 1, adding 0.1-1 part by mass of persulfate and 10-20 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a persulfate solution;

step 2, respectively adding 3-6 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 0.5-2 parts by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 0.3-2 parts by mass of ammonium perfluorooctanoate and 50-80 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the persulfate solution and the solution in the reaction kettle are stirred and mixed, and tetrafluoroethylene gas is introduced into the reaction kettle after the reaction kettle is vacuumized until the pressure in the kettle is 0.3-3 MPa;

step 5, starting stirring of the reaction kettle, heating to 40-60 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 4.5-7.5 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2-3 h, adding one half of the persulfate solution remained in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle, controlling the dropwise adding time to be 30-60 min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 30-50 parts by mass, adding the residual persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 2-3 hours;

step 7, adding 0.5-2 parts by mass of OP-10 and 0.5-2 parts by mass of AEO-9 into a reaction kettle, stirring for 20-40 min, heating the reaction kettle until the liquid begins to boil, recovering steam which is a mixture of water and perfluorooctanoic acid, detecting the content of the perfluorooctanoic acid in the recovered steam, calculating the residual amount of ammonium perfluorooctanoate in the reaction kettle until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; cooling the reaction kettle to room temperature to obtain modified polytetrafluoroethylene emulsion;

further, in the step 1, the persulfate is one or more of potassium persulfate, ammonium persulfate and sodium persulfate;

further, the phosphate is one or more of zinc phosphate, zinc dihydrogen phosphate, ammonium dihydrogen phosphate, sodium phosphate and sodium dihydrogen phosphate;

further, the zirconium salt is one or more of zirconium acetate, zirconium nitrate and ammonium zirconium carbonate;

further, the molybdate is one or more of ammonium molybdate, sodium molybdate and potassium molybdate;

further, the silicate is one or more of sodium silicate, potassium silicate and magnesium silicate;

further, the preparation method of the chromium-free passivator for the electro-galvanized steel strip comprises the following steps: adding phosphate, zirconium salt, molybdate and silicate into deionized water, stirring and dissolving, then dropwise adding the dissolved mixture into the modified polytetrafluoroethylene emulsion in a stirring state, and uniformly mixing to obtain the modified polytetrafluoroethylene emulsion.

The chromium-free passivator prepared by the preparation method is coated on the surface of an electrogalvanized steel strip and dried, and then an organic-inorganic hybrid film is formed on the surface of the electrogalvanized steel strip, wherein the organic film is a silane modified polytetrafluoroethylene film, gamma-methacryloxypropyl triisopropoxysilane participates in the polymerization reaction of tetrafluoroethylene, a silane coupling agent is connected into a polytetrafluoroethylene chain section, the gamma-methacryloxypropyl triisopropoxysilane connects a small amount of tridecafluorooctyltrimethoxysilane into a polytetrafluoroethylene branched chain through a hydrolytic condensation reaction, so that the hydrophobicity and lubricity of the film layer are improved, meanwhile, the hydrolytic condensation rate of the gamma-methacryloxypropyl triisopropoxysilane is slower, part of silicon hydroxyl still remains during high-temperature distillation, the silicon hydroxyl in the film layer has stronger adhesion to the metal surface, and the organic film layer has a certain barrier effect on moisture, oxygen and the like in the air, meanwhile, the modified polytetrafluoroethylene film has a very low friction coefficient, and the dynamic friction coefficient Ud of the modified polytetrafluoroethylene film is less than 0.16 according to GB/T10006-1988 tests by using a Labthink MXD-02 friction coefficient instrument, so that the electro-galvanized steel strip can be endowed with excellent lubricity; the inorganic film is a compact and water-insoluble inorganic conversion film formed by a series of reactions of phosphate, zirconium salt, molybdate and silicate with the zinc layer in the drying process, the inorganic conversion film can prevent the zinc layer from further corrosion, and the organic film layer and the inorganic conversion film cooperate to provide excellent corrosion resistance for the electro-galvanized steel strip.

Compared with the prior art, the invention has the advantages and beneficial effects that:

compared with the traditional passivator, the passivator does not contain hexavalent chromium and trivalent chromium, and compared with the chromium-free passivator for the common galvanized steel sheet, the chromium-free passivator for the galvanized steel sheet takes the modified polytetrafluoroethylene as an organic film layer, and other wax emulsion is not required to be added in a large amount, so that the passivator is good in stability, the passivation film has good corrosion resistance and excellent lubricating property (Ud is 0.05-0.16), and the requirements that the surface of the galvanized steel sheet is not abraded and corroded when the galvanized steel sheet is used for binding goods are met. Compared with common organic resin, the surface of the modified polytetrafluoroethylene emulsion dried to form a film is hydrophobic and oleophobic, so that oxygen in the air and the like can be prevented from further erosion, and meanwhile, the surface of the electrogalvanized steel strip can be endowed with excellent lubricity by the modified polytetrafluoroethylene film.

Drawings

FIG. 1 is a morphology chart of an electro-galvanized steel strip subjected to a salt spray test after being treated with a chromium-free passivator prepared in embodiments 1-5 of the invention and a commercially available chromium-free passivator.

Detailed Description

The present invention is further described in detail with reference to the following examples, which are intended to facilitate the understanding of the present invention by those skilled in the art, but are not intended to limit the present invention.

Example 1 preparation method of chromium-free passivator for electrogalvanized steel strip

In the embodiment, each part by mass is 10 kg;

the first step is as follows: preparing modified polytetrafluoroethylene emulsion:

step 1, adding 0.5 part by mass of potassium persulfate and 12 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a potassium persulfate solution;

step 2, adding 3 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 0.6 part by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 0.5 part by mass of ammonium perfluorooctanoate and 65 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the potassium persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the potassium persulfate solution and the solution in the reaction kettle are stirred and mixed, and tetrafluoroethylene gas is introduced into the reaction kettle after the reaction kettle is vacuumized until the pressure in the kettle is 1 MPa;

step 5, starting stirring of the reaction kettle, heating to 50 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 7.5 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2 hours, adding one half of the potassium persulfate solution left in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle completely, controlling the dropwise adding time to be 40min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 40 parts by mass, adding the residual potassium persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 2.5 hours;

step 7, adding 1.5 parts by mass of OP-10 and 0.5 part by mass of AEO-9 into a reaction kettle, stirring for 25min, heating the reaction kettle until the liquid begins to boil, recovering steam (the steam is a mixture of water and perfluorooctanoic acid), detecting the content of the perfluorooctanoic acid in the recovered steam according to GB 31604.35-2016, and calculating the residual amount of ammonium perfluorooctanoate in the reaction kettle until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; cooling the reaction kettle to room temperature to obtain modified polytetrafluoroethylene emulsion;

through detection, the solid content of the modified polytetrafluoroethylene emulsion is 38.6%, and the viscosity of the emulsion at 25 ℃ is 52.4mPa.s by using a rotational viscometer NDJ-5S;

the second step is that: preparation of chromium-free passivator for electro-galvanized steel strip

At normal temperature (25 ℃), adding 3 parts by mass of sodium phosphate, 1.5 parts by mass of zirconium acetate, 1 part by mass of ammonium molybdate and 8 parts by mass of sodium silicate into 80 parts by mass of deionized water, stirring and dissolving, then dropwise adding the dissolved mixture into 30 parts by mass of modified polytetrafluoroethylene emulsion in a stirring state for 20 minutes, and stirring for 5 minutes after dropwise adding is completed to obtain the chromium-free passivator for the electro-galvanized steel strip.

Example 2 preparation method of chromium-free passivator for electrogalvanized steel strip

In the embodiment, each part by mass is 15 kg;

the first step is as follows: preparing modified polytetrafluoroethylene emulsion:

step 1, adding 0.4 part by mass of potassium persulfate and 18 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a potassium persulfate solution;

step 2, adding 4 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 0.8 part by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 0.8 part by mass of ammonium perfluorooctanoate and 60 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the potassium persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the potassium persulfate solution and the solution in the reaction kettle are stirred and mixed, and tetrafluoroethylene gas is introduced into the reaction kettle after the reaction kettle is vacuumized until the pressure in the kettle is 1 MPa;

step 5, starting stirring of the reaction kettle, heating to 55 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 7 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2.5h, adding one half of the potassium persulfate solution left in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle completely, controlling the dropwise adding time to be 45min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 42 parts by mass, adding the residual potassium persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 2.5 hours;

step 7, adding 1.0 mass part of OP-10 and 0.8 mass part of AEO-9 into a reaction kettle, stirring for 20min, heating the reaction kettle until the liquid begins to boil, recovering steam (the steam is a mixture of water and perfluorooctanoic acid), detecting the content of the perfluorooctanoic acid in the recovered steam according to GB 31604.35-2016, and calculating the residual amount of ammonium perfluorooctanoate in the reaction kettle until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; cooling the reaction kettle to room temperature to obtain modified polytetrafluoroethylene emulsion;

through detection, the solid content of the modified polytetrafluoroethylene emulsion is 39.7%, and the viscosity of the emulsion at 25 ℃ is 58.5mPa.s by using a rotational viscometer NDJ-5S;

the second step is that: preparation of chromium-free passivator for electro-galvanized steel strip

At normal temperature (25 ℃), adding 4 parts by mass of sodium dihydrogen phosphate, 2 parts by mass of zirconium nitrate, 1.5 parts by mass of sodium molybdate and 10 parts by mass of potassium silicate into 100 parts by mass of deionized water, stirring and dissolving, then dropwise adding the dissolved mixture into 38 parts by mass of modified polytetrafluoroethylene emulsion in a stirring state for 15 minutes, and stirring for 10 minutes after dropwise adding is completed to obtain the chromium-free passivator for the electro-galvanized steel strip.

Example 3 preparation method of chromium-free passivator for electrogalvanized steel strip

In the embodiment, each part by mass is 5 kg;

the first step is as follows: preparing modified polytetrafluoroethylene emulsion:

step 1, adding 0.6 part by mass of potassium persulfate and 15 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a potassium persulfate solution;

step 2, adding 5 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 1.0 part by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 0.8 part by mass of ammonium perfluorooctanoate and 60 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the potassium persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the potassium persulfate solution and the solution in the reaction kettle are stirred and mixed, and tetrafluoroethylene gas is introduced into the reaction kettle after the reaction kettle is vacuumized until the pressure in the kettle is 1.5 MPa;

step 5, starting stirring of the reaction kettle, heating to 55 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 5 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2.5h, adding one half of the potassium persulfate solution left in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle completely, controlling the dropwise adding time to be 60min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 38 parts by mass, adding the residual potassium persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 2 hours;

step 7, adding 0.8 mass part of OP-10 and 1.2 mass parts of AEO-9 into a reaction kettle, stirring for 30min, heating the reaction kettle until the liquid begins to boil, recovering steam (the steam is a mixture of water and perfluorooctanoic acid), detecting the content of the perfluorooctanoic acid in the recovered steam according to GB 31604.35-2016, and calculating the residual amount of ammonium perfluorooctanoate in the reaction kettle until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; cooling the reaction kettle to room temperature to obtain modified polytetrafluoroethylene emulsion;

through detection, the solid content of the modified polytetrafluoroethylene emulsion is 39.0%, and the viscosity of the emulsion at 25 ℃ is 55.2mPa.s by using a rotational viscometer NDJ-5S;

the second step is that: preparation of chromium-free passivator for electro-galvanized steel strip

At normal temperature (25 ℃), adding 5 parts by mass of zinc dihydrogen phosphate, 2.5 parts by mass of ammonium zirconium carbonate, 0.8 part by mass of sodium molybdate and 12 parts by mass of sodium silicate into 110 parts by mass of deionized water, stirring and dissolving, then dropwise adding the dissolved mixture into 35 parts by mass of modified polytetrafluoroethylene emulsion in a stirring state for 25 minutes, and stirring for 10 minutes after dropwise adding is completed to obtain the chromium-free passivator for the electro-galvanized steel strip.

Example 4 preparation method of chromium-free passivator for electrogalvanized steel strip

In the embodiment, each mass part is 3 kg;

the first step is as follows: preparing modified polytetrafluoroethylene emulsion:

step 1, adding 0.8 part by mass of potassium persulfate and 20 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a potassium persulfate solution;

step 2, adding 6 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 1.8 parts by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 1.2 parts by mass of ammonium perfluorooctanoate and 75 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the potassium persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the potassium persulfate solution and the solution in the reaction kettle are stirred and mixed, and tetrafluoroethylene gas is introduced into the reaction kettle after the reaction kettle is vacuumized until the pressure in the kettle is 1.5 MPa;

step 5, starting stirring of the reaction kettle, heating to 60 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 6 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2 hours, adding one half of the potassium persulfate solution left in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle completely, controlling the dropwise adding time to be 40min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 48 parts by mass, adding the residual potassium persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 3 hours;

step 7, adding 1.0 mass part of OP-10 and 1.0 mass part of AEO-9 into a reaction kettle, stirring for 25min, heating the reaction kettle until the liquid begins to boil, recovering steam (the steam is a mixture of water and perfluorooctanoic acid), detecting the content of the perfluorooctanoic acid in the recovered steam according to GB 31604.35-2016, and calculating the residual amount of ammonium perfluorooctanoate in the reaction kettle until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; cooling the reaction kettle to room temperature to obtain modified polytetrafluoroethylene emulsion;

through detection, the solid content of the modified polytetrafluoroethylene emulsion is 40.2%, and the viscosity of the emulsion at 25 ℃ is 58.8mPa.s by using a rotational viscometer NDJ-5S;

the second step is that: preparation of chromium-free passivator for electro-galvanized steel strip

At normal temperature (25 ℃), 6 parts by mass of zinc phosphate, 2.5 parts by mass of zirconium nitrate, 2 parts by mass of ammonium molybdate and 10 parts by mass of sodium silicate are added into 105 parts by mass of deionized water and stirred to dissolve, then the dissolved mixture is dripped into 25 parts by mass of modified polytetrafluoroethylene emulsion in a stirring state, the dripping time is 20 minutes, and stirring is carried out for 15 minutes after the dripping is completed, so that the chromium-free passivator for the electro-galvanized steel strip is obtained.

Example 5 preparation method of chromium-free passivator for electrogalvanized steel strip

In the embodiment, each mass part is 3 kg;

the first step is as follows: preparing modified polytetrafluoroethylene emulsion:

step 1, adding 0.8 part by mass of potassium persulfate and 20 parts by mass of deionized water into a No. 1 dripping kettle, and stirring and dissolving to prepare a potassium persulfate solution;

step 2, adding 6 parts by mass of gamma-methacryloxypropyl triisopropoxysilane and 1.8 parts by mass of tridecafluorooctyltrimethoxysilane into a No. 2 dripping kettle, and uniformly mixing;

step 3, adding 1.2 parts by mass of ammonium perfluorooctanoate and 75 parts by mass of deionized water into a reaction kettle, and stirring for dissolving;

step 4, one third of the potassium persulfate solution obtained in the step 1 is dripped into the reaction kettle in the step 3, the potassium persulfate solution and the solution in the reaction kettle are stirred and mixed, and tetrafluoroethylene gas is introduced into the reaction kettle after the reaction kettle is vacuumized until the pressure in the kettle is 1.5 MPa;

step 5, starting stirring of the reaction kettle, heating to 60 ℃, and controlling the flow rate of tetrafluoroethylene gas to be 7.5 parts by mass per hour through a gas mass flow meter; after stirring and reacting for 2 hours, adding one half of the potassium persulfate solution left in the No. 1 dropwise adding kettle into the reaction kettle; dropwise adding the mixed silane coupling agent liquid in the No. 2 dropwise adding kettle into the reaction kettle completely, controlling the dropwise adding time to be 40min, and continuing the heat preservation reaction after the dropwise adding is finished;

step 6, observing a gas mass flow meter, stopping introducing the tetrafluoroethylene gas into the reaction kettle when the total consumption of the tetrafluoroethylene gas is 48 parts by mass, adding the residual potassium persulfate solution into the reaction kettle, and carrying out heat preservation reaction for 3 hours;

step 7, adding 1.0 mass part of OP-10 and 1.0 mass part of AEO-9 into a reaction kettle, stirring for 25min, heating the reaction kettle until the liquid begins to boil, recovering steam (the steam is a mixture of water and perfluorooctanoic acid), detecting the content of the perfluorooctanoic acid in the recovered steam according to GB 31604.35-2016, and calculating the residual amount of ammonium perfluorooctanoate in the reaction kettle until no residual ammonium perfluorooctanoate exists in the liquid of the reaction kettle; cooling the reaction kettle to room temperature to obtain modified polytetrafluoroethylene emulsion;

through detection, the solid content of the modified polytetrafluoroethylene emulsion is 40.2%, and the viscosity of the emulsion at 25 ℃ is 58.8mPa.s by using a rotational viscometer NDJ-5S;

the second step is that: preparation of chromium-free passivator for electro-galvanized steel strip

At normal temperature (25 ℃), adding 50 parts by mass of deionized water into 50 parts by mass of modified polytetrafluoroethylene emulsion in a stirring state, and stirring for 10 minutes to obtain the chromium-free passivator for the electro-galvanized steel strip.

The effect test after the electrogalvanized steel strip is treated by the chromium-free passivator for the electrogalvanized steel strip comprises the following steps:

the used electrogalvanized steel strip of this test is provided for the blue share company of Anshan, and the steel strip width is 33mm, cuts for 180 ~ 200mm according to length for following test:

1. the test method is as follows:

the five electro-galvanized steel strips are dip-coated by the chrome-free passivator for the electro-galvanized steel strips prepared in the examples 1-5 respectively, and after drying at 85 ℃ to form a film, the thickness of the film is controlled to be 600-800 mg per square meter, so that treated electro-galvanized steel strip samples are obtained (i), (ii), (iv). The obtained samples of the treated electrogalvanized steel strips were tested according to the following method [ comparing a chromium-free passivator a (a commercial product i) for a common electrogalvanized steel sheet on the market, in which an organic resin is an acrylic resin, a chromium-free passivator B (a commercial product ii), in which an organic resin is a urethane resin, and an electrogalvanized steel strip which is not passivated ] at the same time:

(1) salt spray resistance test, 72 hour spray test (ASTM B117-2016 standard):

each treated electrogalvanized steel strip sample is required to be free from white rust for 48 hours; the area of white rust is less than or equal to 3 percent in 72 hours;

(2) testing the dynamic friction coefficient Ud of the electro-galvanized steel strip by using a Labthink MXD-02 friction coefficient instrument according to the GB/T10006-1988 standard, wherein the dynamic friction coefficient Ud is required to be between 0.05 and 0.16;

compared with the embodiment 4, the passivation agent of the embodiment 5 is not added with inorganic metal salt, so that the corrosion resistance of the passivation film is poor; the product in the market is a chromium-free passivator mainly used for common galvanized steel sheets, is used on an electrogalvanized steel strip, has better corrosion resistance, but has relatively poorer lubricating property; the market product II is also a chromium-free passivator for common galvanized steel strips, when the chromium-free passivator is used on the galvanized steel strips, the corrosion area of 72h is larger, and the reason is presumed that a zinc layer on the surface of the galvanized steel strips is thinner and looser than a zinc layer on the surface of the galvanized steel strips, so the chromium-free passivator with good corrosion resistance is used on the common galvanized steel strips, the corrosion resistance is not necessarily good when the chromium-free passivator is used on the galvanized steel strips, and meanwhile, the lubricating property cannot meet the use requirement of the galvanized steel strips.

The samples I to IV use the chromium-free passivator for the electro-galvanized steel strip to passivate the surface of the electro-galvanized steel strip, so that the steel strip has good corrosion resistance and lubricity and meets the processing and using requirements.

FIG. 1 is a shape diagram of the samples after salt spray tests (from bottom to top, the samples are numbered sequentially as ((I) ((III)), ((IV)), ((III)) and (III)), and the samples of the electrogalvanized steel strip are subjected to salt spray tests for 72 hours and have no obvious corrosion; seventhly, the steel strip 72h has no obvious corrosion, but the dynamic friction coefficient of the passivated steel strip is higher; the 24h salt spray corrosion area of the No. 24 steel strip is more than 10 percent, the 72h corrosion area of the No. eight steel strip is more than 10 percent, and the corrosion resistance is poor.