Aluminum powder passivating agent and method for preparing the same

Abstract

The present application relates to a kind of aluminum powder passivator and its preparation method, the passivator is graft polymer and includes the following functional units: anchoring functional unit, hydrophilic functional unit and hydrophobic functional unit;Anchoring functional unit is selected from styryl phosphoric acid, fluorinated styryl phosphoric acid, or its combination;Hydrophilic functional unit is selected from 2-methyl-2-acrylic acid, 2-methyl-2-methyl acrylate, or its combination;Hydrophobic functional unit is selected from styrene, acrylate monomer, methacrylate monomer, or its combination.Compared with prior art, the present application uses styryl phosphoric acid or fluorinated styryl phosphoric acid as anchoring functional unit, wherein the phosphoric acid group is directly connected to the carbon main chain, the content of functional phosphoric acid group can be simply controlled during polymerization, effectively combined with the surface of aluminum powder, improve the coating rate of aluminum powder, and it contains styrene itself, can be used as hydrophobic group, enhance the hydrophobic function, effectively improve the passivation effect, increase the stability of aluminum powder slurry.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology and relates to an aluminum powder passivating agent. Specifically, this invention relates to a phosphate-containing graft polymer-based aluminum powder passivating agent suitable for water-based self-cleaning coatings. Background Technology

[0002] With the increasing environmental awareness and pursuit of a better life, the research, development and application of water-based self-cleaning coatings will receive more attention.

[0003] Aluminum powder provides a good metallic visual effect to metallic paint films and has excellent decorative properties, especially in industrial and automotive coatings, where it is widely used. In oil-based metallic paints, aluminum powder exists stably. However, if aluminum powder used in oil-based paints is directly dispersed in water, it easily reacts with water to generate hydrogen gas, making it very unstable and requiring passivation. Typically, water-based metallic paints are placed in sealed containers. Unpassivated or poorly passivated aluminum powder reacts with water to generate hydrogen gas, increasing the pressure inside the container and potentially causing container bulging. Furthermore, hydrogen gas is explosive, posing a safety hazard. Simultaneously, the surface of the aluminum powder is corroded by water molecules, resulting in a poor mirror finish and weakening its metallic texture. The longer the paint is stored, the more severe these problems become. Moreover, with prolonged storage, the aluminum powder is prone to settling, affecting its usability.

[0004] To address the aforementioned issues, coating the surface of aluminum powder with organic passivating agents is a crucial strategy. This coating reduces the likelihood of collisions between aluminum powder and water molecules, lowers the reaction rate, and stabilizes the aluminum powder in water-based coatings. Passivating agents are primarily phosphate ester polymers, such as those described in US Patent 4675358, which prepares phosphate ester polymers through the condensation polymerization of phosphoric acid and polyhydroxy compounds; and Chinese Patent CN105542077A, which uses phosphoric acid-modified acrylic monomers to prepare phosphate ester polymers via free radical polymerization. However, in these reported phosphate ester organic passivating agents, the phosphate ester units are only located at the chain ends or in the middle, which affects the passivation effect on aluminum powder, leading to easy sedimentation of the coated aluminum powder in water-based coatings. Therefore, in view of the above-mentioned defects in the existing technology, there is an urgent need in the field for a more rational design of passivating agent structure. Chinese patent CN1196752C designed a phosphoric acid esterification graft copolymer to solve the sedimentation problem of aluminum powder slurry. However, its phosphoric acid esterification step is to react with the active groups of the polymer with phosphoric acid, phosphorus pentoxide, pyrophosphate, etc. after the graft polymer is formed. Due to the multi-component nature of phosphoric acid, the degree of esterification reaction is not easy to control, which will form more network compounds, affecting anchoring passivation. At the same time, the esterification reaction cannot distinguish the active hydroxyl groups of nonionic hydrophilic units. When phosphoric acid esterifies with nonionic hydrophilic units, it seriously affects its passivation effect. Moreover, the esterified polymer or the monomer phosphoric acid modified (meth)acrylate (acrylamide) etc. described in the above patent has multiple atoms, including oxygen atoms, between the phosphate group and the carbon backbone, which affects the hydrophobic function.

[0005] Therefore, there is an urgent need in the field for an aluminum powder passivator with excellent passivation properties for use in water-based coatings. Summary of the Invention

[0006] The purpose of this invention is to provide an aluminum powder passivating agent with excellent passivation properties for use in water-based coatings, as well as its preparation and application.

[0007] In a first aspect, the present invention provides an aluminum powder passivating agent, said passivating agent being a grafted polymer and comprising the following functional units:

[0008] 1) Anchoring functional unit;

[0009] 2) Hydrophilic functional unit; and

[0010] 3) Hydrophobic functional unit;

[0011] The anchoring functional unit is selected from styrene-phosphoric acid, fluorinated styrene-phosphoric acid, or a combination thereof;

[0012] The hydrophilic functional unit is selected from 2-methyl-2-acrylic acid, methyl 2-methyl-2-acrylate, or a combination thereof;

[0013] The hydrophobic functional unit is selected from styrene, acrylate monomers, methacrylate monomers, or combinations thereof.

[0014] Preferably, in the grafted polymer, based on the total weight of the passivating agent, the weight content of the anchoring functional unit is 2-30 wt%; the weight content of the hydrophilic functional unit is 2-20 wt%; and the weight content of the hydrophobic functional unit is 2-30 wt%.

[0015] Preferably, the acrylate monomer is selected from the group consisting of butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, or combinations thereof.

[0016] Preferably, the methacrylate monomers are selected from the group consisting of methyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, or combinations thereof.

[0017] Preferably, the hydrophobic unit further includes a fluorinated monomer, wherein the fluorinated monomer is selected from the group consisting of fluorinated styrene, fluorinated methacrylic acid monomers, fluorinated acrylic acid monomers, or combinations thereof.

[0018] Preferably, it has one or more features selected from the group consisting of:

[0019] 1) The Mn of the passivating agent is 1000-30000;

[0020] 2) The Mw of the passivating agent is 3000-150000;

[0021] 3) The dispersibility of the passivating agent is 1-10;

[0022] 4) In the grafted polymer, the weight content of styrene groups is 1-30 wt%;

[0023] 5) The phosphate group content in the grafted polymer is 2-20 wt%.

[0024] Preferably, it has one or more features selected from the group consisting of:

[0025] 1) The solid content of the passivating agent is 45-70 wt%;

[0026] 2) The acid value of the passivating agent is 100-250 mg KOH / g.

[0027] A second aspect of the present invention provides a method for preparing a passivating agent as described in the first aspect of the present invention, comprising the following steps:

[0028] 1) Provide a first mixture, a second mixture, and a third mixture;

[0029] The first mixture comprises a first solvent, an anchoring monomer, and a hydrophilic monomer;

[0030] The second mixture comprises a second solvent, a hydrophobic monomer, an optional anchoring monomer, and an optional hydrophilic monomer;

[0031] The third mixture comprises a third solvent and an initiator;

[0032] 2) After heating the first mixture to a first temperature, the second mixture and the third mixture are simultaneously added dropwise to it. After the addition is complete, the mixture is kept at the temperature for a first time and then cooled to room temperature. The mixture is then filtered to obtain the passivating agent.

[0033] Preferably, in step 2), the first temperature is 70-100℃ and the first time is 5-100min.

[0034] A third aspect of the present invention provides the use of the passivating agent as described in the first aspect of the present invention for passivating aluminum powder in water-based metal coatings.

[0035] It should be understood that, within the scope of this invention, the above-described technical features of this invention and the technical features specifically described below (such as in the embodiments) can be combined with each other to form new or preferred technical solutions. Due to space limitations, they will not be described in detail here. Detailed Implementation

[0036] The present invention will now be described in detail with reference to specific embodiments. However, these embodiments do not limit the present invention, and any structural, methodological, or functional modifications made by those skilled in the art based on these embodiments are included within the scope of protection of the present invention.

[0037] In this specification, "comprising" or "containing" means that, in addition to the ingredients described, the polymer may contain other components that impart different properties to the polymer.

[0038] Through long-term and in-depth research, the inventors unexpectedly prepared an aluminum powder passivating agent containing phosphate groups. This passivating agent can efficiently passivate aluminum powder in water-based coatings, significantly improving the overall performance (such as stability and safety) of the resulting water-based coatings. Based on this, the inventors completed this invention.

[0039] The aluminum powder passivating agent of the present invention is a grafted polymer, which is a colorless or pale yellow viscous liquid and comprises the following functional units:

[0040] 1) Anchoring functional unit;

[0041] 2) Hydrophilic functional unit; and

[0042] 3) Hydrophobic functional unit;

[0043] Among them, the anchoring function unit is

[0044] Styrenic acid (structural formula is) ) or fluorinated styrene-based phosphoric acid (structural formula is Furthermore, the weight content of the anchoring functional unit is 2-30 wt% (based on the total weight of the passivating agent), preferably 8-25 wt%, and more preferably 10-22 wt%.

[0045] The hydrophilic functional unit is 2-methyl-2-acrylic acid or methyl 2-methyl-2-acrylate, and further, the weight content of the hydrophilic unit is 2-20 wt%, preferably 8-16 wt%, and more preferably 10-12 wt%.

[0046] The hydrophobic functional unit is styrene, acrylate monomers, or methacrylate monomers. Further, the weight content of the hydrophobic unit is 2-30 wt%, preferably 10-20 wt%, and more preferably 14-18 wt%.

[0047] In the hydrophobic functional unit, the acrylate monomers are selected from the group consisting of butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, or combinations thereof; the methacrylate monomers are selected from the group consisting of methyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, or combinations thereof.

[0048] It is worth mentioning that the reason for using styrene-based phosphoric acid or fluorinated styrene-based phosphoric acid as the anchoring functional unit is that the phosphate groups in styrene-based phosphoric acid and fluorinated styrene-based phosphoric acid are directly connected to the carbon backbone. During polymerization, the content of functional phosphate groups can be easily controlled, effectively combining with the aluminum powder surface and improving the aluminum powder coating rate. Moreover, styrene-based phosphoric acid or fluorinated styrene-based phosphoric acid itself contains styrene, which can act as a hydrophobic group to enhance the hydrophobic function, effectively improve the passivation effect, and increase the stability of the aluminum powder paste.

[0049] In another preferred embodiment of the present invention, the hydrophobic functional unit may further include a fluorinated monomer selected from the group consisting of fluorinated styrene, fluorinated methacrylate monomers, fluorinated acrylic monomers, or combinations thereof. The fluorinated styrene is 2,3,4,5,6-pentafluorostyrene; the fluorinated methacrylate monomers are selected from the group consisting of dodecafluoroheptyl methacrylate, hexafluorobutyl methacrylate, hexafluoroisopropyl methacrylate, octafluoropentyl methacrylate, perfluorohexylethyl methacrylate, perfluorooctylethyl methacrylate, perfluoroalkyl ethyl methacrylate, or combinations thereof; and the fluorinated acrylic monomers are selected from the group consisting of 2,3,3-trifluoroacrylate, hexafluorobutyl acrylate, hexafluoroisopropyl acrylate, octafluoropentyl acrylate, perfluorohexylethyl acrylate, perfluorooctylethyl acrylate, perfluoroalkyl ethyl acrylate, or combinations thereof.

[0050] Preferably, the fluorine content is 0.5-12 wt% based on the total weight of the passivating agent, more preferably 3-10 wt%, and even more preferably 3.5-8 wt%.

[0051] During the polymerization reaction, fluorine atoms are introduced into the polymer chain of the passivating agent by adding fluorine-containing monomers. Due to the introduction of fluorine, the compatibility with fluorocarbon resins in water-based self-cleaning coatings can be effectively improved, and the passivation effect of the passivating agent can also be improved.

[0052] The present invention also provides a method for preparing the aluminum powder passivating agent as described above, which includes the following steps:

[0053] S1. Provide a first mixture, a second mixture, and a third mixture;

[0054] The first mixture comprises a first solvent, an anchoring monomer, and a hydrophilic monomer;

[0055] The second mixture comprises a second solvent, a hydrophobic monomer, an optional anchoring monomer, and an optional hydrophilic monomer;

[0056] The third mixture contains a third solvent and an initiator;

[0057] S2. After heating the first mixture to a first temperature, the second mixture and the third mixture are simultaneously added dropwise to it. After the addition is complete, the mixture is kept at the temperature for a first time and then cooled to room temperature. The mixture is then filtered to obtain the passivating agent.

[0058] In detail, in step S1, styrene-based phosphoric acid or fluorinated styrene-based phosphoric acid is used as the anchoring functional unit, 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate polymer macromonomer (CAS NO.25086-15-1) is used as the hydrophilic functional unit, and (fluorinated) styrene and (fluorinated, methyl) acrylic monomers are used as the hydrophobic functional units.

[0059] The first solvent, the second solvent, and the third solvent may be the same or different, and are independently selected from the group consisting of methyl isopentyl ketone, methyl isobutyl ketone, methyl n-pentyl ketone, or combinations thereof.

[0060] The initiator is selected from: azo compounds, peroxides, or combinations thereof.

[0061] Azo compounds are selected from: azobisisobutyronitrile, azobisisoheptanenitrile, azobisisovalerate, or combinations thereof.

[0062] Peroxides are selected from: benzoyl peroxide (such as dibenzoyl peroxide), di-tert-butyl peroxide, dicumyl peroxide, tert-butyl peroxypentanoate, or combinations thereof.

[0063] In step S2, a portion of the anchoring monomer, hydrophilic monomer, and first solvent are added to the reaction vessel. A portion of the hydrophobic monomer, anchoring monomer, hydrophilic monomer, and second solvent are added to the dropping tank. The initiator and third solvent are added to the initiator tank. The reaction vessel is heated to 70-100°C. The second mixture in the dropping tank and the third mixture in the initiator tank are simultaneously added dropwise to the reaction vessel. After the addition is completed, the mixture is kept at this temperature for 5-100 minutes and then cooled to room temperature. The mixture is filtered, and the resulting filtrate is the passivating agent solution.

[0064] Preferably, the time for adding the second mixture in the dropping vessel is 100-300 min, more preferably 150-200 min, and even more preferably 160-180 min. The time for adding the third mixture in the initiator vessel is 120-320 min, more preferably 160-220 min, and even more preferably 180-200 min.

[0065] The aluminum powder passivating agent obtained by the present invention has one or more characteristics selected from the group consisting of:

[0066] 1) The Mn of the aluminum powder passivating agent is 1000-30000, preferably 1500-20000, and even more preferably 2000-1600;

[0067] 2) The Mw of the aluminum powder passivating agent is 3000-150000, preferably 5000-120000, and even more preferably 7000-100000;

[0068] 3) The dispersion of the aluminum powder passivating agent is 1-10, preferably 1.3-8, and more preferably 1.5-6.5;

[0069] 4) In the grafted polymer, the weight content of styrene groups is 1-30 wt%, preferably 2-20 wt%, and more preferably 4-15 wt%.

[0070] 5) In the grafted polymer, the weight content of phosphate groups is 2-20 wt%, preferably 3-10 wt%, and more preferably 4-8 wt%;

[0071] 6) The solid content of the aluminum powder passivating agent is 45-70 wt%, preferably 48-60 wt%, and more preferably 50-55 wt%.

[0072] 7) The acid value of the aluminum powder passivating agent is 100-250 mgKOH / g, preferably 120-230 mgKOH / g, and even more preferably 140-210 mgKOH / g.

[0073] The present invention also provides an application of an aluminum powder passivating agent for passivating aluminum powder in water-based metal coatings. An accelerated test was conducted on aluminum powder slurry containing the above passivating agent over 5 days. Under constant temperature conditions of 50°C, the amount of hydrogen generated after 5 days was less than 15%.

[0074] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Experimental methods in the following embodiments, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. Unless otherwise stated, percentages and parts are by weight.

[0075] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as are familiar to those skilled in the art. Furthermore, any methods and materials similar to or equivalent to those described herein may be applied to the methods of this invention. The preferred embodiments and materials described herein are for illustrative purposes only.

[0076] Example 1: Preparation of passivating agent P1

[0077] Add 86g styrene-based phosphoric acid, 55g of a polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 280g MIBK to a reaction flask and stir for 30 minutes. Set aside. Add 87g styrene, 98g hexafluorobutyl methacrylate, 50g 2-ethylhexyl methacrylate, 44g styrene-based phosphoric acid, 55g of a polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 100g MIBK to a monomer flask and stir for 30 minutes. Set aside. Add 45g benzoyl peroxide and 100g MIBK solution to an initiator flask and stir for 30 minutes. Set aside. The reaction flask was heated to 80 degrees Celsius, and then the liquids from both flasks were added dropwise. The liquid in the monomer flask was added over 180 minutes, and the liquid initiator was added over 195 minutes. After the addition was completed, the mixture was kept at the same temperature for 30 minutes, cooled to room temperature, and filtered to obtain a passivating agent solution P1 with a molecular weight of approximately 4465 Mn, approximately 20577 Mw, and a dispersion of 4.6.

[0078] Example 2: Preparation of passivating agent P2

[0079] Add 65g of fluorinated styrene-based phosphoric acid, 55g of the polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 280g of MIBK to a reaction flask and stir for 30 minutes. Set aside. Add 87g of styrene, 62g of butyl methacrylate, 50g of 2-ethylhexyl methacrylate, 36g of butyl acrylate, 65g of fluorinated styrene-based phosphoric acid, 55g of the polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 100g of MIBK to a monomer flask and stir for 30 minutes. Set aside. Add 45g of benzoyl peroxide and 100g of MIBK solution to an initiator flask and stir for 30 minutes. Set aside. The reaction flask was heated to 80 degrees Celsius, and then the liquids from both flasks were added dropwise. The liquid in the monomer flask was added over 180 minutes, and the liquid initiator was added over 195 minutes. After the addition was completed, the mixture was kept at the same temperature for 30 minutes, cooled to room temperature, and filtered to obtain a passivating agent solution P2 with a molecular weight of approximately 2569 Mn, approximately 11501 Mw, and a dispersion of approximately 4.5.

[0080] Example 3: Preparation of passivating agent P3

[0081] Add 44g of fluorinated styrene-based phosphoric acid, 55g of a polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 280g of MIBK to a reaction flask and stir for 30 minutes. Set aside. Add 87g of styrene, 62g of butyl methacrylate, 50g of 2-ethylhexyl methacrylate, 36g of butyl acrylate, 86g of fluorinated styrene-based phosphoric acid, 55g of a polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 100g of MIBK to a monomer flask and stir for 30 minutes. Set aside. Add 45g of benzoyl peroxide and 100g of MIBK solution to an initiator flask and stir for 30 minutes. Set aside. The reaction flask was heated to 90 degrees Celsius, and then the liquids from both flasks were added dropwise. The liquid in the monomer flask was added over 180 minutes, and the liquid initiator was added over 195 minutes. After the addition was completed, the mixture was kept at the same temperature for 30 minutes, cooled to room temperature, and filtered to obtain a passivating agent solution P3 with a molecular weight of approximately 2018 Mn, approximately 7939 Mw, and a dispersion of approximately 3.9.

[0082] Example 4: Preparation of passivating agent P4

[0083] Add 44g of fluorinated styrene-based phosphoric acid, 65g of the polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 280g of MIBK to a reaction flask and stir for 30 minutes. Set aside. Add 87g of styrene, 62g of butyl methacrylate, 50g of 2-ethylhexyl methacrylate, 36g of butyl acrylate, 86g of fluorinated styrene-based phosphoric acid, 55g of the polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 100g of MIBK to a monomer flask and stir for 30 minutes. Set aside. Add 35g of benzoyl peroxide and 100g of MIBK solution to an initiator flask and stir for 30 minutes. Set aside. The reaction flask was heated to 80 degrees Celsius, and then the liquids from both flasks were added dropwise. The liquid in the monomer flask was added over 180 minutes, and the liquid initiator was added over 195 minutes. After the addition was completed, the mixture was kept at the same temperature for 30 minutes, then cooled to room temperature. The solution was filtered to obtain a passivating agent solution P4 with a molecular weight of approximately 15036 Mn, approximately 94486 Mw, and a dispersion of approximately 6.2.

[0084] Example 5: Preparation of passivating agent P5

[0085] Add 44g styrylphosphoric acid, 55g of the polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 280g MAK to a reaction flask and stir for 30 minutes. Set aside. Add 116g 2,3,4,5,6-pentafluorostyrene, 32g hexafluorobutyl methacrylate, 12g butyl methacrylate, 50g 2-ethylhexyl methacrylate, 36g butyl acrylate, 86g styrylphosphoric acid, 55g of the polymer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate, and 100g MAK to a monomer flask and stir for 30 minutes. Set aside. Add 45g benzoyl peroxide and 100g MAK solution to an initiator flask and stir for 30 minutes. Set aside. The reaction flask was heated to 90 degrees Celsius, and then the liquids from both flasks were added dropwise. The liquid in the monomer flask was added over 180 minutes, and the liquid initiator was added over 195 minutes. After the addition was completed, the mixture was kept at the same temperature for 30 minutes, cooled to room temperature, and filtered to obtain a passivating agent solution P5 with a molecular weight of approximately 7488 Mn, approximately 12310 Mw, and a dispersion of approximately 1.64.

[0086] The passivating agents P1-P5 obtained in Examples 1-5 have the properties shown in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] Note: The content of each group is in weight percentage, based on the total weight of the passivating agent solution.

[0091] Example 6 uses the above passivating agents P1, P2, P3, P4, and P5 to prepare different aluminum powder pastes;

[0092] The aluminum powder paste was prepared according to the formula in Table 2, with the proportions being by weight.

[0093] Table 2 Formulation for aluminum slurry preparation

[0094] Dimethylisopropanolamine 0.2 Aluminum powder 634A-V 20 passivating agent 6.2 Dimethylisopropanolamine 0.2 Polyurethane resin Daotan 1236 38 Deionized water 19.2

[0095] The preparation process of aluminum powder paste is as follows: Adjust the pH value of the solvent ethylene glycol butyl ether to between 6.8 and 7.5. Add aluminum powder to ethylene glycol butyl ether by stirring and disperse for 30 minutes to ensure complete dispersion of aluminum powder without sedimentation or clumping. Add passivating agent P1, or P2, or P3, or P4, or P5 respectively, and stir for 30 minutes. Adjust the pH value to 4.8-5.5 using dimethyl isopropanolamine, and continue stirring for another 30 minutes. Add polyurethane emulsion Daotan1236 and deionized water, and stir for 30 minutes to obtain aluminum powder paste.

[0096] Take 200g of the above aluminum powder slurry and add it to the aluminum powder gas generation measuring device. Under constant temperature of 50 degrees Celsius, after 5 days, the amount of hydrogen generated is obtained by collecting the volume of liquid in the upper air chamber. The hydrogen content of the aluminum powder slurry corresponding to passivator P1 is 31ml, the hydrogen content of the aluminum powder slurry corresponding to passivator P2 is 22ml, the hydrogen content of the aluminum powder slurry corresponding to passivator P3 is 12ml, the hydrogen content of the aluminum powder slurry corresponding to passivator P4 is 15ml, and the hydrogen content of the aluminum powder slurry corresponding to passivator P5 is 5ml.

[0097] Table 3

[0098] hydrogen content 31ml 22ml 12ml 15ml 5ml

[0099] In the above experiment, 200g of aluminum powder slurry contains approximately 1mol of aluminum. Assuming all the aluminum reacts with water, the volume of hydrogen gas produced is approximately 33.6L. After using the passivating agent described above, we can see from Table 3 that under high temperature conditions of 50 degrees Celsius, the amount of hydrogen gas produced is between 5 and 31ml, accounting for 0.014% to 0.093% of 33.6L. The experiment shows that the passivating agent has a significant passivation effect. At the same time, the passivation effect varies with factors such as the molecular weight of the passivating agent, phosphorus content, and fluorine content. In subsequent practical production applications, the passivation effect of aluminum powder can be finely controlled by adjusting these factors.

[0100] General testing methods

[0101] Molecular weight and dispersity

[0102] Dissolve an appropriate amount of sample in 20 mL of mobile phase. After the sample is completely dissolved, filter it through a glass syringe and inject the filtrate into a sample tube for later use. Then, analyze the sample using a GPC-2000 gel permeation chromatograph.

[0103] passivating agent solids

[0104] First, weigh the weighing paper. Then, weigh approximately 1g of sample and place it on the weighing paper, recording the mass. Distribute the sample evenly on the surface of the weighing paper, and then quickly place it in an electric heating drying oven set at 110℃. After 1 hour, remove the weighing paper, weigh it again, and record the data. The formula for calculating the solid content is shown below:

[0105]

[0106] X: Solid content of the sample to be tested, %;

[0107] W: Mass of the sample to be tested before drying, in g;

[0108] W1: Mass of the weighed paper, in g;

[0109] W2: Total mass of the sample to be tested and the weighing paper after drying, in g.

[0110] Passivating agent acid value

[0111] Take 0.5 g of sample and add 20-50 ml of benzene alcohol solution (volume ratio ml: toluene: 95% ethanol = 2:1).

[0112] After diluting and completely dissolving the sample, titrate with 0.1 mol / L potassium hydroxide ethanol solution (KOH-CH3CH2OH). The titration endpoint is reached when the colorless solution turns into a light pink color.

[0113] AV (acid value) = {(C × L) ÷ M} ÷ X

[0114] L------------number of milliliters of titrant consumed

[0115] M---------The weight of the resin sample taken

[0116] C----------Titrate coefficient

[0117] X---------Solid content

[0118] Passivation effect (hydrogen gas emission)

[0119] Place 200g of the prepared aluminum powder slurry into a 1L conical flask. Fill a 100ml graduated cylinder with deionized water and invert it in a room temperature water bath. Clamp the gas delivery tube in the middle, insert one end into the bottom of the graduated cylinder, and insert the other end into the sealing plug at the top of the conical flask. Place the sealed conical flask with the gas delivery tube into a 50°C water bath. Open the gas delivery tube clamp and let it sit for five days. After cooling the 50°C water bath to 25°C, read the gas volume in the graduated cylinder.

[0120] All documents mentioned in this invention are incorporated herein by reference as if each document were individually incorporated by reference. Furthermore, it should be understood that after reading the foregoing teachings of this invention, those skilled in the art can make various alterations or modifications to this invention, and these equivalent forms also fall within the scope defined by the appended claims.

Claims

1. An aluminum powder passivating agent, characterized in that, The passivating agent is a grafted polymer and includes the following functional units: 1) Anchoring functional unit; 2) Hydrophilic functional unit; and 3) Hydrophobic functional unit; The anchoring functional unit is selected from styrene-phosphoric acid, fluorinated styrene-phosphoric acid, or a combination thereof; The hydrophilic functional unit is a polymer macromonomer of 2-methyl-2-acrylic acid and methyl 2-methyl-2-acrylate; The hydrophobic functional unit is selected from styrene, acrylate monomers, methacrylate monomers, or combinations thereof.

2. The aluminum powder passivating agent as described in claim 1, characterized in that, In the grafted polymer, based on the total weight of the passivating agent, the weight content of the anchoring functional unit is 2-30 wt%; the weight content of the hydrophilic functional unit is 2-20 wt%; the weight content of the hydrophobic functional unit is 2-30 wt%; and the remainder is solvent and initiator.

3. The aluminum powder passivating agent as described in claim 1, characterized in that, The acrylate monomers are selected from the group consisting of butyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, or combinations thereof.

4. The aluminum powder passivating agent as described in claim 1, characterized in that, The methacrylate monomers are selected from the group consisting of methyl methacrylate, hydroxyethyl methacrylate, glycidyl methacrylate, butyl methacrylate, 2-ethylhexyl methacrylate, or combinations thereof.

5. The aluminum powder passivating agent as described in claim 1, characterized in that, The hydrophobic functional unit further includes fluorinated monomers, which are selected from the group consisting of fluorinated styrene, fluorinated methacrylic acid monomers, fluorinated acrylic acid monomers, or combinations thereof.

6. The aluminum powder passivating agent as described in claim 1, characterized in that, It has one or more characteristics selected from the following group: 1) The Mn content of the aluminum powder passivating agent is 1000-30000; 2) The Mw of the aluminum powder passivating agent is 3000-150000; 3) The dispersion of the aluminum powder passivating agent is 1-10; 4) In the grafted polymer, the weight content of styrene groups is 1-30 wt%; 5) The phosphate group content in the grafted polymer is 2-20 wt%.

7. The aluminum powder passivating agent as described in claim 1, characterized in that, It has one or more characteristics selected from the following group: 1) The solid content of the aluminum powder passivating agent is 45-70 wt%; 2) The acid value of the aluminum powder passivating agent is 100-250 mg KOH / g.

8. A method for preparing the aluminum powder passivating agent as described in claim 1, characterized in that, Includes the following steps: 1) Provide a first mixture, a second mixture, and a third mixture; The first mixture comprises a first solvent, an anchoring monomer, and a hydrophilic monomer; The second mixture comprises a second solvent, a hydrophobic monomer, an optional anchoring monomer, and an optional hydrophilic monomer; The third mixture comprises a third solvent and an initiator; 2) After heating the first mixture to a first temperature, the second mixture and the third mixture are simultaneously added dropwise to it. After the addition is complete, the mixture is kept at the temperature for a first time and then cooled to room temperature. The mixture is then filtered to obtain the passivating agent.

9. The preparation method according to claim 8, characterized in that, In step 2), the first temperature is 70-100°C and the first time is 5-100 min.

10. The use of the aluminum powder passivating agent as described in claim 1, characterized in that, Aluminum powder used for passivation in water-based metallic coatings.

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