A circulating water phosphorus-free cleaning pre-film agent and a preparation method thereof

Abstract

The application relates to the technical field of pre-film agents, and particularly discloses a circulating water phosphorus-free cleaning pre-film agent and a preparation method thereof, which is prepared by mixing raw materials including the following components in parts by mass: deionized water 50-60 parts, organic modified component 20-30 parts, arabic gum 3-5 parts and sodium gluconate 5-8 parts; the preparation steps include the following: taking the deionized water, the organic modified component and the sodium gluconate, mixing under a nitrogen atmosphere, stirring, then adding the arabic gum, and continuously stirring to obtain the product; when used, the organic modified component can be spread on the surface of an iron pipeline to form a protective conversion film. After being treated by the circulating water phosphorus-free cleaning pre-film agent, the conversion film has an inhibition rate of greater than or equal to 95.05%, and can realize long-term protection of the iron pipeline for water circulation.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pre-film agents, and more particularly to a circulating water phosphorus-free cleaning pre-film agent and a preparation method thereof. BACKGROUND

[0002] The pre-film agent is mainly used for pipe isolation treatment of industrial circulating water systems, and plays a role in protecting the metal pipes (such as carbon steel, cast iron, etc.) of the circulating cooling water system from corrosion and fouling. In use, the pre-film agent can form a dense protective film on the surface of the metal pipe, avoiding direct contact between the water body and the pipe wall, thereby significantly reducing the pipe corrosion rate, prolonging the service life of the pipe and improving the heat exchange efficiency.

[0003] Common pre-film agents mainly include chromate type, molybdate type, silicate type and phosphorus-containing type, etc.; among them, the phosphorus-containing pre-film agent (such as polyphosphate, organic phosphonate, etc.) has low cost and fast film forming speed, so it has high application value. However, after treatment by this type of pre-film agent, there are still a large amount of phosphorus elements in the waste liquid discharged, and direct discharge of the waste liquid can easily lead to eutrophication of the water body; and since phosphorus / phosphonate is prone to deposit and form scale in high-hardness water, it can aggravate the pipe blockage and is not conducive to long-term use of the pipe.

[0004] The Chinese patent application file with the publication number CN116121739A discloses a weak acid water quality zinc-containing phosphorus-free iron-based pre-film agent and a preparation method thereof. In the scheme, the pre-film agent without phosphorus components is obtained by mixing amino acid polymers with bactericides and other components, which can reduce the risk of pipe fouling and ultimately achieve the effect of promoting stable operation of the circulating water system.

[0005] In the above-mentioned file, although the problem of phosphorus pollution and pipe blockage is alleviated by controlling the raw materials to be strictly phosphorus-free and adding anti-fouling components, the service life of the pre-film agent is not long because the amino acid polymers in the main components of the pre-film agent have poor water-oxygen barrier property, and the active molecules of the pre-film agent are easily affected by the dissolved oxygen environment of the circulating water pipe. Therefore, it is necessary to find a circulating water phosphorus-free cleaning pre-film agent that can improve the water-oxygen barrier property of the pre-film agent for iron pipes and prolong the service life of the pre-film agent. SUMMARY

[0006] In order to further improve the water-oxygen barrier property of the pre-film agent for iron pipes and prolong the service life of the pre-film agent, the present application provides a circulating water phosphorus-free cleaning pre-film agent and a preparation method thereof.

[0007] In the first aspect, the present application provides a preparation method of a circulating water phosphorus-free cleaning pre-film agent, which adopts the following technical scheme:

[0008] The application discloses a preparation method of a circulating water phosphorus-free cleaning pre-film agent, which is prepared by mixing raw materials including the following components in mass fraction: 50-60 parts of deionized water, 20-30 parts of an organic modified component, 3-5 parts of gum arabic and 5-8 parts of sodium gluconate.

[0009] The deionized water, the organic modified component and the sodium gluconate are mixed under a nitrogen atmosphere and stirred, then the gum arabic is added and continuously stirred to obtain the pre-film agent.

[0010] The preparation steps of the organic modified component include the following steps.

[0011] [S01] acylated cysteine is taken, dispersed, and pH is adjusted; then a carboxyl activator is added, and the mixture is stirred and treated at a high temperature; then allyl amine is added, and the reaction is continuously carried out; then the bottom layer precipitate is taken by centrifugation, washed with alcohol and dried under reduced pressure to obtain a complex.

[0012] [S02] mixed solvents are taken, and then a vinylidene chloride monomer and the complex are added and stirred; after being heated, an initiator is added and the reaction is carried out; then the vinylidene chloride monomer and the complex are added and the reaction is continuously carried out; and then the low-oligomer emulsion is obtained after being cooled.

[0013] [S03] the low-oligomer emulsion and an acrylic monomer are taken, and the mixture is initiated and treated; then the acrylic monomer is added and the reaction is continuously carried out at a high temperature; then the mixture is cooled, and pH is adjusted; after being vacuum degassed, the mixture is sequentially subjected to deacylation and demulsification, and then the organic phase is collected and dried after being washed with alcohol.

[0014] By adopting the technical scheme, the organic modified component is composed of a hydrophilic polyacrylic acid end obtained by polymerization of an acrylic monomer and a modified low-oligomer vinylidene chloride hydrophobic end; the organic modified component can obtain a pre-film agent active component with an "oil-in-water" structure after being dispersed in a water environment of the pre-film agent. In the water dispersion environment of the pre-film agent, due to the difference in hydrophilicity and hydrophobicity of the molecular chain segments, the polyacrylic acid chain segment with high hydrophilicity in the organic modified component tends to be on the outer layer of the group, and the modified low-oligomer vinylidene chloride with high hydrophobicity is attached to the inside of the group structure and is isolated from the water environment; the stability of the "oil-in-water" structure is maintained through the agglomeration and wrapping. 3+Forming a chelate structure, so that the pre-film agent is attached to the iron pipe surface; the added arabic gum can be adsorbed on the water-oil interface of the organic modified component due to its molecular amphiphilic structure, reduce the interfacial tension, promote the spread of the "oil-in-water" structure, and expose the internal hydrophobic structure; the high electronegativity chlorine group of the hydrophobic structure can block the external water and oxygen, preventing the invasion of the film layer; at the same time, through polymerization reaction, the mercapto structure introduced in the oligomer of vinylidene chloride segment can be exposed and cross-linked to form disulfide bond (-S-S-) with the dissolved oxygen in the circulating water as the oxygen source, and the outside hydrophobic end is cross-linked into a network, further strengthening the compactness of the pre-film agent film, and finally achieving the effect of prolonging the service life of the pre-film agent.

[0015] Preferably, in the step [S01], the preparation step of acylated cysteine includes the following steps: taking L-cysteine, dispersing with dimethyl sulfoxide, adding a basic catalyst and acetic anhydride, reacting at low temperature, then adjusting the pH, separating the organic phase, drying, rotary evaporation, recrystallization, and then filtering the solid part to obtain acylated cysteine after drying.

[0016] The basic catalyst is one of triethylamine and pyridine.

[0017] By adopting the above technical scheme, the protection of the mercapto group on L-cysteine can be realized. Under the action of a basic catalyst, the active mercapto group structure on L-cysteine can form a protective structure through acylation reaction with acetic anhydride, avoiding the deactivation of the mercapto group due to side reactions in subsequent reactions.

[0018] Preferably, the recrystallization operation is: adding anhydrous ethanol, dispersing, adjusting the temperature to 3-4℃, and treating for 6-8h.

[0019] Preferably, the mass-volume ratio of dimethyl sulfoxide, L-cysteine, basic catalyst and acetic anhydride used is 45ml:10g:(3.2-4.6)ml:(12-15)ml.

[0020] Preferably, in the step [S01], the pH is adjusted to 6.2-6.8.

[0021] Preferably, the carboxyl activating agent is obtained by mixing 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide and N-hydroxysuccinimide in a mass ratio of 1:(1-1.5).

[0022] By adopting the technical scheme, 1-ethyl-(3-dimethylaminopropyl) carbodiimide can form an intermediate with the active carboxyl group on the acylated protected cysteine, the intermediate further reacts with N-hydroxysuccinimide to obtain a stable ester structure; in the subsequent reaction, the primary amino group on the allylamine can react with the ester structure to introduce a double bond structure on the cysteine molecule, providing a double bond condition for subsequent participation in the polymerization of the vinylidene chloride monomer.

[0023] Preferably, in the step [S02], the mixed solvent is obtained by mixing deionized water, Tween-20, sodium dodecyl sulfate and sodium sulfite according to a mass-volume ratio of 40 ml: (2-3) g: (1-1.5) g: (0.2-0.3) g;

[0024] The mass ratio of the initiator, the first added vinylidene chloride monomer and the complex is (0.15-0.2):(12-15):(2.5-2.7);

[0025] The additional vinylidene chloride monomer and the complex are 20%-35% and 10%-12% of the first added amount, respectively.

[0026] By adopting the technical scheme, the mixed solvent can provide an emulsification environment to promote the emulsion polymerization reaction of the vinylidene chloride and the complex; and the batch addition of the reactants can promote the mild reaction, so that the final low molecular product is obtained, and the over-polymerization of the product is avoided.

[0027] Preferably, in the step [S03], the deacylation treatment is: adding a deacylation agent and continuously reacting for 1-2 h.

[0028] The deacylation agent is obtained by mixing hydroxylamine hydrochloride and ethylenediaminetetraacetic acid according to a mass ratio of (5-7):1.

[0029] By adopting the technical scheme, under the action of the deacylation agent, the protected sulfhydryl structure on the L-cysteine is restored to reactivity and exposed when the organic modified component "oil-in-water" structure collapses, and participates in the densification process after the pre-film agent is formed into a film.

[0030] Preferably, in the step [S03], the demulsification operation is: adding a sodium chloride solution with a mass concentration of 10% to the system, standing at room temperature for 3-5 min, and then centrifuging at 3000-4500 rpm for 10-15 min.

[0031] By adopting the technical scheme, the sodium chloride solution with a mass concentration of 10% as a strong electrolyte treatment liquid can destroy the water-soluble balance, reduce the stability of the emulsion, and then be treated by centrifugation to realize the demulsification separation of the organic modified component.

[0032] In a second aspect, the application provides a phosphorus-free cleaning pre-film agent for circulating water prepared by the above preparation method.

[0033] In summary, the present application has the following beneficial effects:

[0034] 1. The present application adopts a water-dispersible organic modified component to obtain a pre-film agent active component with an "oil-in-water" structure. In use, the polyacrylic acid on the outer side of the "oil-in-water" structure of the organic modified component can be attached to the surface of the iron pipeline through chelation, and the addition of gum arabic can promote the spreading of the "oil-in-water" structure, exposing the inner layer of the hydrophobic modified oligomer of vinylidene chloride, preventing external water and dissolved oxygen from invading the film layer, and enhancing the water and oxygen barrier ability of the iron pipeline after pre-film treatment.

[0035] 2. In the present application, the acylated cysteine is preferably reacted with allylamine to obtain a complex, and the complex is further reacted with vinylidene chloride monomer to obtain modified oligomer of vinylidene chloride; after deacyl protection, the active sulfhydryl group exposed by the organic modified component is cross-linked to form a disulfide bond (-S-S-) with dissolved oxygen in the circulating water as the oxygen source, and the outer hydrophobic end is cross-linked into a network, further strengthening the compactness of the pre-film agent film, and ultimately achieving the effect of prolonging the service life of the pre-film agent.

[0036] 3. After the pre-film agent of the present application is used, the conversion film has a corrosion inhibition rate of ≥95.05%, which can achieve a long-lasting protection effect on the iron pipeline for water circulation. BRIEF DESCRIPTION OF DRAWINGS

[0037] Figure 1 The corrosion rate and corrosion inhibition rate of the pretreated piece after being treated with the pre-film agents of Examples 1-4 and Comparative Examples 1-3 of the present application.

[0038] Figure 2 The iron ion elution rate of the pretreated piece after being treated with the pre-film agents of Example 2 and Comparative Examples 1-3 of the present application. DETAILED DESCRIPTION

[0039] Preparation Example 1

[0040] Take 100 ml three-necked bottle, add 45 ml dimethyl sulfoxide, nitrogen bubbling 15 min, then add 10 g L-cysteine, 3.2 ml triethylamine and 12 ml acetic anhydride, adjust the magnetic stirring speed to 150 rpm, temperature 10 ℃, reaction 2 h, adjust the system pH to 7 with 0.5 mol / L hydrochloric acid, then separate the organic phase, add 0.5 g anhydrous sodium sulfate to remove residual moisture, then filter the liquid part, 45 ℃ rotary evaporation to dry the solvent part, then add 50 ml anhydrous ethanol, adjust the temperature to 3 ℃, stand for 6 h, then filter the solid part, vacuum drying in the oven at 40 ℃, then disperse with 20 ml deionized water, adjust the system pH to 6.2 with 0.05 mol / L hydrochloric acid, then add 8.5 g carboxyl activator, adjust the magnetic stirring speed to 100 rpm, temperature 30 ℃, treat for 1.5 h, then add 3 ml allylamine, continue to react for 2 h, then centrifuge at 1500 rpm for 30 min, wash the bottom layer precipitate with 4 ℃ cold ethanol for 2 times, and dry at 50 ℃ under reduced pressure for 2 h to obtain the complex.

[0041] The carboxyl activator is obtained by mixing 1-ethyl-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide according to a mass ratio of 1:1.

[0042] Preparation Example 2

[0043] Take 100 ml three-necked bottle, add 45 ml dimethyl sulfoxide, nitrogen bubbling 15 min, then add 10 g L-cysteine, 4.3 ml pyridine and 14 ml acetic anhydride, adjust the magnetic stirring speed to 150 rpm, temperature 12 ℃, reaction 2 h, adjust the system pH to 7 with 0.5 mol / L hydrochloric acid, then separate the organic phase, add 0.5 g anhydrous sodium sulfate to remove residual moisture, then filter the liquid part, 45 ℃ rotary evaporation to dry the solvent part, then add 50 ml anhydrous ethanol, adjust the temperature to 3.5 ℃, stand for 8 h, then filter the solid part, vacuum drying in the oven at 40 ℃, then disperse with 20 ml deionized water, adjust the system pH to 6.5 with 0.05 mol / L hydrochloric acid, then add 8.5 g carboxyl activator, adjust the magnetic stirring speed to 100 rpm, temperature 30 ℃, treat for 1.5 h, then add 3.2 ml allylamine, continue to react for 2.5 h, then centrifuge at 1500 rpm for 30 min, wash the bottom layer precipitate with 4 ℃ cold ethanol for 2 times, and dry at 60 ℃ under reduced pressure for 2.5 h to obtain the complex.

[0044] The carboxyl activator is obtained by mixing 1-ethyl-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide according to a mass ratio of 1:1.2.

[0045] Preparation Example 3

[0046] Take 100ml three-necked bottle, add 45ml dimethyl sulfoxide, nitrogen bubbling 15min, then add 10g L-cysteine, 4.6ml pyridine and 15ml acetic anhydride, adjust the magnetic stirring speed to 150rpm, temperature 15℃, reaction 4h, adjust the system pH to 7 with 0.5mol / L hydrochloric acid, then separate the organic phase, add 0.5g anhydrous sodium sulfate to remove residual moisture, then filter the liquid part, 45℃ rotary evaporation to dry the solvent part, then add 50ml anhydrous ethanol, adjust the temperature to 4℃, stand for 8h, then filter the solid part, vacuum drying in the oven at 40℃, then disperse with 20ml deionized water, adjust the system pH to 6.8 with 0.05mol / L hydrochloric acid, then add 8.7g carboxyl activator, adjust the magnetic stirring speed to 100rpm, temperature 35℃, treat for 2h, then add 3.5ml allylamine, continue to react for 2.5h, then centrifuge at low speed of 1500rpm for 30min, wash the bottom layer precipitate with 4℃ cold ethanol for 2 times, dry at 60℃ under reduced pressure for 3h to obtain the complex.

[0047] The carboxyl activator is obtained by mixing 1-ethyl-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide according to a mass ratio of 1:1.5.

[0048] Preparation Example 4

[0049] Take 100ml three-necked bottle, add 45ml dimethyl sulfoxide, nitrogen bubbling 15min, then add 10g L-cysteine, 4.6ml pyridine and 15ml acetic anhydride, adjust the magnetic stirring speed to 150rpm, temperature 15℃, reaction 4h, adjust the system pH to 7 with 0.5mol / L hydrochloric acid, then separate the organic phase, add 0.5g anhydrous sodium sulfate to remove residual moisture, then filter the liquid part, 45℃ rotary evaporation to dry the solvent part, then add 50ml anhydrous ethanol, adjust the temperature to 4℃, stand for 8h, then filter the solid part, vacuum drying in the oven at 40℃, then disperse with 20ml deionized water, adjust the system pH to 6.8 with 0.05mol / L hydrochloric acid, then add 8.7g carboxyl activator, adjust the magnetic stirring speed to 100rpm, temperature 35℃, treat for 2h, then add 3.5ml allylamine, continue to react for 2.5h, then centrifuge at low speed of 1500rpm for 30min, wash the bottom layer precipitate with 4℃ cold ethanol for 2 times, dry at 60℃ under reduced pressure for 3h to obtain the complex.

[0050] The carboxyl activator is obtained by mixing 1-ethyl-(3-dimethylaminopropyl) carbodiimide and N-hydroxysuccinimide according to a mass ratio of 1:1.2.

[0051] Example 1

[0052] Take 50g of deionized water, 20g of organic modified component, 5g of sodium gluconate, mix under nitrogen atmosphere, adjust the magnetic stirring speed to 100rpm, disperse for 20min, then add 3g of gum arabic, continue to disperse for 10min, to get the circulating water non-phosphorus cleaning pre-film agent.

[0053] The preparation steps of the organic modified component in this example are as follows:

[0054] Take 45ml of mixed solvent, add 12g of vinylidene chloride monomer and 2.5g of complex, adjust the magnetic stirring speed to 250rpm, continue for 10min, then increase the system temperature to 50℃, add 0.15g of potassium persulfate to initiate, treat for 20min, then add 2.4g of vinylidene chloride and 0.25g of complex, continue to react for 10min, then stop heating, cool after standing, then add 7.2g of acrylic acid monomer, then add 10ml of 0.05g / ml ammonium persulfate dropwise, adjust the magnetic stirring speed to 100rpm, increase the system temperature to 50℃ at a rate of 1.5℃ / min, then keep constant temperature, continue stirring for 10min, then add 2.5g of acrylic acid monomer, continue to increase the system temperature to 70℃, react for 2h, then stop heating, cool to room temperature, then adjust the system pH to 7.2, then vacuum degassing for 10min, then add 1.5g of deacylating agent, control the magnetic stirring speed to 120rpm, continue to react for 1h, then add 20ml of 10% sodium chloride solution to the system, stand at room temperature for 3min, then centrifuge at 3000rpm for 10min, collect the organic phase, wash twice with anhydrous ethanol, dry to get the organic modified component.

[0055] The complex in this example is prepared by Preparation Example 1.

[0056] Among them, gum arabic (model: DL-A-30HY) is provided by Guangdong Dingsheng Food Ingredients Co., Ltd. The mixed solvent is obtained by mixing deionized water, Tween-20, sodium dodecyl sulfate and sodium sulfite according to the mass volume ratio of 40ml:2g:1g:0.2g. The deacylating agent is obtained by mixing hydroxylamine hydrochloride and ethylenediaminetetraacetic acid according to the mass ratio of 5:1.

[0057] Example 2

[0058] Take 55g of deionized water, 24g of organic modified component, 6g of sodium gluconate, mix under nitrogen atmosphere, adjust the magnetic stirring speed to 100rpm, disperse for 25min, then add 3g of gum arabic, continue to disperse for 15min, to get the circulating water non-phosphorus cleaning pre-film agent.

[0059] The preparation steps of the organic modified component in this example are as follows:

[0060] Take 45 ml of mixed solvent, add 14 g of vinylidene chloride monomer and 2.5 g of complex, adjust the magnetic stirring speed to 250 rpm, continue for 20 min, then increase the system temperature to 55°C, add 0.15 g of potassium persulfate, initiate treatment for 25 min, then add 4.9 g of vinylidene chloride and 0.3 g of complex, continue to react for 12 min, then stop heating, after cooling, add 7.8 g of acrylic acid monomer, then add 0.05 g / ml of ammonium persulfate 10 ml dropwise, adjust the magnetic stirring speed to 100 rpm, increase the system temperature to 50°C at a rate of 2°C / min, then keep constant temperature, continue stirring for 10 min, then add 2.7 g of acrylic acid monomer, continue to increase the system temperature to 75°C, react for 3 h, then stop heating, after cooling to room temperature, adjust the system pH to 7.2, then vacuum degassing for 10 min, then add 1.7 g of deacylating agent, control the magnetic stirring speed to 120 rpm, continue to react for 2 h, then add 20 ml of 10% sodium chloride solution to the system, stand at room temperature for 5 min, then centrifuge at 4000 rpm for 12 min, collect the organic phase, wash twice with anhydrous ethanol, dry to obtain the organic modified component.

[0061] The complex in this example was prepared by Preparation Example 2.

[0062] Among them, the gum arabic (model: DL-A-30HY) was provided by Guangdong Dingsheng Food Ingredients Co., Ltd. The mixed solvent was obtained by mixing deionized water, Tween-20, sodium dodecyl sulfate and sodium sulfite according to the mass volume ratio of 40 ml:2 g:1 g:0.3 g. The deacylating agent was obtained by mixing hydroxylamine hydrochloride and ethylenediaminetetraacetic acid according to the mass ratio of 6:1.

[0063] Example 3

[0064] Take 45 ml of mixed solvent, add 14 g of vinylidene chloride monomer and 2.5 g of complex, adjust the magnetic stirring speed to 250 rpm, continue for 20 min, then increase the system temperature to 55°C, add 0.15 g of potassium persulfate, initiate treatment for 25 min, then add 4.9 g of vinylidene chloride and 0.3 g of complex, continue to react for 12 min, then stop heating, after cooling, add 7.8 g of acrylic acid monomer, then add 0.05 g / ml of ammonium persulfate 10 ml dropwise, adjust the magnetic stirring speed to 100 rpm, increase the system temperature to 50°C at a rate of 2°C / min, then keep constant temperature, continue stirring for 10 min, then add 2.7 g of acrylic acid monomer, continue to increase the system temperature to 75°C, react for 3 h, then stop heating, after cooling to room temperature, adjust the system pH to 7.2, then vacuum degassing for 10 min, then add 1.7 g of deacylating agent, control the magnetic stirring speed to 120 rpm, continue to react for 2 h, then add 20 ml of 10% sodium chloride solution to the system, stand at room temperature for 5 min, then centrifuge at 4000 rpm for 12 min, collect the organic phase, wash twice with anhydrous ethanol, dry to obtain the organic modified component.

[0065] The preparation steps of the organic modified component in this example are as follows:

[0066] Take 45 ml of mixed solvent, add 15 g of vinylidene chloride monomer and 2.7 g of complex, adjust the magnetic stirring speed to 250 rpm, continue for 20 min, then increase the system temperature to 55°C, add 0.2 g of potassium persulfate, initiate treatment for 25 min, then add 3 g of vinylidene chloride and 0.27 g of complex, continue to react for 12 min, then stop heating, after cooling, add 7.8 g of acrylic acid monomer, then add 0.05 g / ml of ammonium persulfate 10 ml, adjust the magnetic stirring speed to 100 rpm, increase the system temperature to 50°C at a rate of 2.3°C / min, then constant temperature, continue stirring for 10 min, then add 2.7 g of acrylic acid monomer, continue to increase the system temperature to 75°C, react for 3 h, then stop heating, after cooling to room temperature, adjust the system pH to 7.5, then vacuum degassing for 10 min, then add 1.7 g of deacylating agent, control the magnetic stirring speed to 120 rpm, continue to react for 2 h, then add 20 ml of 10% sodium chloride solution to the system, stand at room temperature for 5 min, then centrifuge at 4500 rpm for 15 min, collect the organic phase, wash twice with anhydrous ethanol, dry to obtain the organic modified component.

[0067] The complex in this example was prepared by Preparation Example 3.

[0068] Among them, the gum arabic (model: DL-A-30HY) is provided by Guangdong Dingsheng Food Ingredients Co., Ltd. The mixed solvent is obtained by mixing deionized water, Tween-20, sodium dodecyl sulfate and sodium sulfite according to the mass volume ratio of 40 ml:3 g:1.5 g:0.3 g. The deacylating agent is obtained by mixing hydroxylamine hydrochloride and ethylenediaminetetraacetic acid according to the mass ratio of 7:1.

[0069] Example 4

[0070] Take 45 ml of mixed solvent, add 15 g of vinylidene chloride monomer and 2.7 g of complex, adjust the magnetic stirring speed to 250 rpm, continue for 20 min, then increase the system temperature to 55°C, add 0.2 g of potassium persulfate, initiate treatment for 25 min, then add 3 g of vinylidene chloride and 0.27 g of complex, continue to react for 12 min, then stop heating, after cooling, add 7.8 g of acrylic acid monomer, then add 0.05 g / ml of ammonium persulfate 10 ml, adjust the magnetic stirring speed to 100 rpm, increase the system temperature to 50°C at a rate of 2.3°C / min, then constant temperature, continue stirring for 10 min, then add 2.7 g of acrylic acid monomer, continue to increase the system temperature to 75°C, react for 3 h, then stop heating, after cooling to room temperature, adjust the system pH to 7.5, then vacuum degassing for 10 min, then add 1.7 g of deacylating agent, control the magnetic stirring speed to 120 rpm, continue to react for 2 h, then add 20 ml of 10% sodium chloride solution to the system, stand at room temperature for 5 min, then centrifuge at 4500 rpm for 15 min, collect the organic phase, wash twice with anhydrous ethanol, dry to obtain the organic modified component.

[0071] The preparation steps of the organic modified component in this example are as follows:

[0072] Take 45 ml of mixed solvent, add 12 g of vinylidene chloride monomer and 2.6 g of complex, adjust the magnetic stirring speed to 250 rpm, continue for 10 min, then increase the system temperature to 50℃, add 0.15 g of potassium persulfate, initiate treatment for 20 min, then add 3 g of vinylidene chloride and 0.27 g of complex, continue to react for 10 min, then stop heating, after cooling, add 7.2 g of acrylic acid monomer, then add 0.05 g / ml of ammonium persulfate 10 ml, adjust the magnetic stirring speed to 100 rpm, increase the system temperature to 50℃ at a rate of 1.5℃ / min, then keep constant temperature, continue stirring for 10 min, then add 2.5 g of acrylic acid monomer, continue to increase the system temperature to 70℃, react for 2 h, then stop heating, cool to room temperature, then adjust the system pH to 7.2, then vacuum degassing for 10 min, then add 1.5 g of deacylating agent, control the magnetic stirring speed to 120 rpm, continue to react for 1 h, then add 20 ml of 10% sodium chloride solution to the system, stand at room temperature for 5 min, then centrifuge at 3000 rpm for 15 min, collect the organic phase, wash twice with anhydrous ethanol, dry to obtain the organic modified component.

[0073] The complex in this example was prepared by Preparation Example 4.

[0074] Among them, the gum arabic (model: DL-A-30HY) is provided by Guangdong Dingsheng Food Ingredients Co., Ltd. The mixed solvent is obtained by mixing deionized water, Tween-20, sodium dodecyl sulfate and sodium sulfite according to a mass-volume ratio of 40 ml:2 g:1 g:0.2 g. The deacylating agent is obtained by mixing hydroxylamine hydrochloride and ethylenediaminetetraacetic acid according to a mass ratio of 5:1.

[0075] Comparative Example 1

[0076] The difference between this comparative example and Example 1 is only that the circulating water phosphorus-free cleaning pre-film agent is composed of the following mass of raw materials: deionized water 75 g, organic modified component 5 g, gum arabic 10 g, sodium gluconate 12 g.

[0077] The remaining steps are the same as Example 1.

[0078] Comparative Example 2

[0079] The difference between this comparative example and Example 1 is only that an equal amount of polyacrylic acid is used instead of the organic modified component.

[0080] Among them, the polyacrylic acid (model K-732, average molecular weight 6000) is provided by Lubrizol.

[0081] The remaining steps are the same as Example 1.

[0082] Comparative Example 3

[0083] The present comparative example differs from Example 1 only in that an equal amount of Tween-80 is used instead of gum arabic.

[0084] Tween-80 (80% content) is provided by Sainuo Experimental Instrument Co., Ltd.

[0085] The remaining steps are the same as in Example 1.

[0086] Performance detection test

[0087] Pre-treatment: The pre-film test piece is a type I test piece of 20# carbon steel, and the pre-treatment test piece is obtained by processing according to the standard HG / T3523.

[0088] Pre-film test: Take the circulating water phosphorus-free cleaning pre-film agent of Examples 1-4 and Comparative Examples 1-3, and prepare a pre-film treatment solution according to an effective pre-film agent component of 250 mg / L. Then, use each group of pre-film treatment solutions to perform a rotating hanging piece pre-film treatment on the pre-treatment test piece. The pre-film time is set to 24 h, and then the pre-film is stopped to obtain a pre-film treatment piece.

[0089] 1. Pre-film quality

[0090] 1.1 Wrinkling and foaming performance

[0091] Test method: visual inspection.

[0092] 1.2 Pre-film thickness

[0093] According to GB / T13452.2-2008, the pre-film thickness of the pre-film treatment pieces of Examples 1-4 and Comparative Examples 1-3 is determined.

[0094] 1.3 Impact resistance

[0095] According to GB / T1732-2020, a 1000g weight is used, the impact height is set to 50cm, and the impact resistance of the pre-film treatment pieces of Examples 1-4 and Comparative Examples 1-3 is tested. After testing, whether cracks, wrinkles and peeling phenomena are observed determines whether the pre-film passes the impact test.

[0096] 1.4 Scratch resistance

[0097] According to GB / T9286-2021, the scratch resistance of the pre-film treatment pieces of Examples 1-4 and Comparative Examples 1-3 is tested, and the visual rating is performed. The rating standard is as follows: 0 level: no scratches visible; 1 level: slight scratches (only surface damage); 2 level: obvious scratches (coating surface damage, not penetrated); 3 level: severe scratches (coating partially penetrated, test piece slightly exposed); 4 level: complete failure (coating large area peeling, test piece completely exposed).

[0098] Table 1. Pre-film quality test results of Examples 1-4 and Comparative Examples 1-3

[0099]

[0100] 2. Anti-corrosion performance test

[0101] The anti-corrosion performance of the pre-film treated pieces of Examples 1-4 and Comparative Examples 1-3 was tested according to GB / T18175-2014. Untreated pre-treatment test pieces were set as a blank group. The air flow rate in each test cup was controlled at 300 mL / min, and the test time was 120 h. After the test period, the corrosion rate and corrosion inhibition rate of each group of pre-treatment pieces were calculated, and the test results are shown in Table 2. Figure 1

[0102] 3. Pore condition test

[0103] The pre-film formed a conversion film surface with pores. The pre-treatment test pieces could be corroded by contacting with water and oxygen through the pores, and iron ions were dissolved. Therefore, by monitoring the dissolution rate of iron ions of the pre-treatment test pieces in the treatment environment, the pore condition of the film after pre-film treatment could be characterized.

[0104] A 500 ml beaker was taken, 200 ml of deionized water, 45 ml of 0.75 mol / L potassium thiocyanate, and 35 ml of 0.5 mol / L acetic acid solution were added, and then the pH was adjusted to 3.2, and stirred uniformly to obtain the test solution. The pre-film treated pieces of Example 2 and Comparative Examples 1-3 were immersed in the test solution, and air was introduced into the test solution at a rate of 200 ml / min. After a period of time, the test solution was taken and the absorbance of the solution at a wavelength of 485 nm was measured by a spectrophotometer. The Fe 3+ ion concentration in the test solution was calculated by a standard curve to characterize the pore condition of the film, and the test results are shown in Table 3. Figure 2

[0105] As can be seen from the analysis of Examples 1-4 and Comparative Examples 1-3 and in combination with Table 1, the surface quality test results of the conversion film obtained after treating the pre-film agent according to the example scheme are excellent, indicating that the pre-film agent according to the example scheme has better spreading ability on the pre-treatment test pieces. In Comparative Example 3, Tween-80 surfactant was used instead of gum arabic, and after treatment, the surface of the pre-film treated piece was slightly wrinkled, and the conversion film anti-scratch ability was also reduced, indicating that the promotion effect of Tween-80 on the spreading of "oil-in-water" structure is not as good as that of gum arabic. In Comparative Example 2, polyacrylic acid was directly used instead of the organic modified component. Due to the strong hydrophilic property of polyacrylic acid itself, polyacrylic acid tends to disperse in the water phase during the pre-film process, and it is difficult to form a stable conversion film on the surface of the pre-treatment test piece. Therefore, the conversion film obtained has the lowest thickness and the worst quality.

[0106] As can be seen from the analysis of Examples 1-4 and Comparative Examples 1-3 and in combination with​​Figure 1 It can be seen that the corrosion of the pretreatment piece of Comparative Example 2 is the most serious in all test groups, followed by Comparative Example 1. It is indicated that the pretreatment film forming agent of Comparative Example 2 has the lowest water and oxygen blocking effect in the test environment, and the dissolved oxygen is more likely to penetrate the conversion film to corrode the pretreated test piece to be protected; the pretreatment film forming agent of Comparative Example 1 has a blocking effect on dissolved oxygen, but due to the low proportion of the organic modification component in the pretreatment film forming agent, the effect is correspondingly reduced. In all example schemes, the corrosion rate of the pretreated test piece after the pretreatment film forming treatment of Example 2 is the lowest, and the corrosion inhibition rate is at the highest level in all example groups.

[0107] Example 2 and Comparative Examples 1-3 are analyzed and combined Figure 2 It can be seen that the iron ion dissolution rate of the pretreated test piece is positively correlated with the treatment time, indicating that the water and oxygen corrosion continues during the test; the iron ion dissolution rate of Comparative Example 2 changes at a rate close to a constant value, because the porosity of the conversion film obtained on the pretreated test piece after the pretreatment film forming agent treatment of Comparative Example 2 remains unchanged, and the speed of iron ion dissolution from the conversion film pores due to water and oxygen corrosion is relatively uniform. The iron ion dissolution rate-test time curves of Comparative Example 1, Comparative Example 3 and Example 2 all show a trend of slowing down the growth rate and tending to be stable, which can indicate that the pores on the conversion film appear to be blocked as the test proceeds, because the mercapto structure existing on the hydrophobic end of the outer layer of the conversion film is crosslinked into a network, the conversion film is gradually densified, which prevents the dissolution of iron ions, and finally realizes the long-acting pretreatment film protection effect.

[0108] The specific embodiments are only an explanation of the present application, and are not a limitation of the present application. Those skilled in the art can make modifications to the embodiments without creative contribution after reading the present specification, and as long as the modifications are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A method for preparing a phosphorus-free cleaning pre-film agent for circulating water, characterized by, Preparation by mixing raw materials including the following mass parts: deionized water 50-60 parts, organic modification component 20-30 parts, acacia 3-5 parts, sodium gluconate 5-8 parts, the preparation steps including the following: Take deionized water, organic modification component and sodium gluconate, mix under nitrogen atmosphere, stir, then add acacia, continue stirring, and get it; The preparation steps of the organic modification component include the following: [S01] Take acylated protected cysteine, disperse, adjust pH, then add carboxyl activator, stir under heating, then add allylamine, continue to react, then centrifuge to take the bottom precipitate, alcohol wash and reduce pressure drying to get the complex; [S02] Take mixed solvent, first add vinylidene chloride monomer and complex, stir, then add initiator after heating, react, then add vinylidene chloride monomer and complex, continue to react, then get the oligomer emulsion after standing and cooling; [S03] Take oligomer emulsion and acrylic acid monomer, initiate treatment, then add acrylic acid monomer, continue to react under heating, then cool, adjust pH, vacuum degassing, then deacyl, demulsification in turn, collect organic phase, then alcohol wash and dry, and get it.

2. The method for preparing a phosphorus-free cleaning pre-film agent for circulating water according to claim 1, characterized in that, In the step [S01], the preparation steps of acylated protected cysteine include the following: take L-cysteine, disperse with dimethyl sulfoxide, add alkaline catalyst and acetic anhydride, react under low temperature, then adjust pH, separate to take organic phase, then dry, rotary evaporation, recrystallization in turn, and get solid part by suction filtration, then oven dry to get acylated protected cysteine.

3. The method of claim 2, wherein the phosphorus-free cleaning pre-film agent for circulating water is prepared by adding 0.1 to 1.0 parts by weight of the surfactant to 100 parts by weight of the water. The alkaline catalyst is one of triethylamine and pyridine.

4. The method for preparing a phosphorus-free pre-filming agent for circulating water cleaning according to claim 2, characterized in that, The recrystallization operation is: add anhydrous ethanol, disperse, adjust temperature to 3-4℃, and treat for 6-8h.

5. The method for preparing a phosphorus-free pre-filming agent for circulating water cleaning according to claim 2, characterized in that, The mass volume ratio of dimethyl sulfoxide, L-cysteine, alkaline catalyst and acetic anhydride used is 45ml:10g:(3.2-4.6)ml:(12-15)ml.

6. The method for preparing a phosphorus-free pre-filming agent for circulating water cleaning according to claim 1, characterized in that, In the step [S01], the pH is adjusted to 6.2-6.8; the carboxyl activator is obtained by mixing 1-ethyl-(3-dimethylaminopropyl) carbonyl diimide and N-hydroxysuccinimide according to mass ratio 1:(1-1.5).

7. The method for preparing a phosphorus-free pre-filming agent for circulating water cleaning according to claim 1, characterized in that, In the step [S02], the mixed solvent is obtained by mixing deionized water, Tween-20, sodium dodecyl sulfate and sodium sulfite according to mass volume ratio 40ml:(2-3)g:(1-1.5)g:(0.2-0.3)g; the mass ratio of initiator, first added vinylidene chloride monomer and complex is (0.15-0.2):(12-15):(2.5-2.7); the additional vinylidene chloride monomer and complex are 20%-35% and 10%-12% of the first added amount respectively.

8. The method of claim 1, wherein the method is characterized by: In the step [S03], the deacyl treatment is: add deacyl agent, continue to react for 1-2h; the deacyl agent is obtained by mixing hydroxylamine hydrochloride and ethylenediaminetetraacetic acid according to mass ratio (5-7):

1.

9. The method of claim 1, wherein the method is characterized by: In the step [S03], the demulsification operation is: add sodium chloride solution with mass concentration of 10% to the system, stand for 3-5min at room temperature, then centrifuge at 3000-4500rpm for 10-15min.

10. A phosphorous-free rinse pre-film for recirculating water cleaning prepared by the method of any one of claims 1-9.

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