Highly resistant and thixotropic emulsion with core-shell structure and preparation method thereof

Abstract

The present invention discloses a highly resistant and thixotropic emulsion with a core-shell structure and a preparation method thereof. The emulsion comprises the following components in parts by weight: 60-80 parts of deionized water, 0.3-2.5 parts of a reactive anionic emulsifier, 10-20 parts of butyl acrylate, 40-60 parts of methyl methacrylate, 1-2 parts of hydroxyethyl methacrylate, 0.5-2 parts of lauric methacrylate, 10-20 parts of methacrylic acid, 0.1-1 parts of an initiator, and 1-5 parts of N,N-dimethylethanolamine. The use of long-chain monomers improves the water resistance of the emulsion. Furthermore, because the addition of long-chain monomers improves water resistance, the amount of carboxylic acid monomer can be increased, thereby widening the adjustable range of thixotropy.

Description

Technical Field

[0001] The present invention relates to the field of chemical industry, in particular to a high-resistance and thixotropic emulsion with a core-shell structure and a preparation method thereof. Background Art

[0002] In aluminum silver powder baking paint, in order to ensure the metallic gloss effect of the paint surface, it is necessary to achieve directional arrangement of aluminum powder and / or silver powder in the coating. In the existing technology, in order to achieve directional arrangement of aluminum powder, a large amount of aluminum silver powder directing agent needs to be added to the coating, but this will reduce the gloss and other properties of the coating. In recent years, some thixotropic emulsions have appeared on the market, which reduce the amount of directing agent used. Thixotropic emulsions need to have a core-shell structure, with carboxylic acid in the shell and carboxylic acid radicals extending outside the shell. In the later stage, alkali neutralization is used to achieve thickening and thixotropy. The amount and degree of neutralization of carboxylic acid determine the thixotropy, but existing thixotropic emulsions often dare not add too much carboxylic acid, which will affect the water resistance of the emulsion film, and a small amount of carboxylic acid leads to insufficient thixotropy. How to solve this contradiction is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0003] In order to overcome the shortcomings of the prior art, the purpose of the present invention is to provide a highly resistant and thixotropic emulsion with a core-shell structure, which uses long-chain monomers to improve the water resistance of the emulsion. At the same time, because the water resistance is improved by adding long-chain monomers, the amount of carboxylic acid monomers can be increased, and the adjustable range of thixotropy is expanded.

[0004] In order to solve the above problems, the technical solutions adopted by the present invention are as follows:

[0005] A high-resistance and thixotropic emulsion with a core-shell structure is prepared by comprising the following components in parts by weight: 60-80 parts of deionized water, 0.3-2.5 parts of a reactive anionic emulsifier, 10-20 parts of butyl acrylate, 40-60 parts of methyl methacrylate, 1-2 parts of hydroxyethyl methacrylate, 0.5-2 parts of lauric methacrylate, 10-20 parts of methacrylic acid, 0.1-1 part of an initiator, and 1-5 parts of N,N-dimethylethanolamine.

[0006] Preferably, the reactive anionic emulsifier is any one of DNS-458, SR-10, DNS-86 and MA-80.

[0007] Preferably, the initiator is any one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0008] The present invention also includes a method for preparing the emulsion described in any one of the above items, comprising the steps of:

[0009] S101 was added to the container A part of the deionized water, under stirring conditions, added part of the emulsifier, high-speed dispersion 20-40min, then added part of butyl acrylate, part of methyl methacrylate, part of hydroxyethyl methacrylate and all of lauryl methacrylate, continue to disperse at high speed 20-40min to obtain a core layer pre-emulsion;

[0010] S102. Under stirring conditions, part of the deionized water and the remaining emulsifier were added to container B, the temperature was raised to 85-90 ° C, part of the initiator was added, and after the initiator was added, the core layer pre-emulsion prepared in step S101 was added dropwise to container B. The addition time was controlled within 1-2h. After the addition was completed, the mixture was incubated for 1h.

[0011] S103 was added to the container C remaining butyl acrylate, the remaining methyl methacrylate, the remaining hydroxyethyl methacrylate and all methacrylic acid, stirred for 5min to obtain a shell monomer mixture; to the container D was added a portion of deionized water and the remaining initiator, stirred to obtain an initiator aqueous solution;

[0012] S104. After the insulation of container B in step S102 is completed, the temperature is lowered to 70-75°C and the shell monomer mixture prepared in step S103 is added dropwise over 15 minutes. After the addition, the initiator aqueous solution prepared in step S103 is added dropwise over 5-10 minutes. The mixture is then incubated for 2 hours.

[0013] S105. After the insulation is completed, cool to below 50°C, add the remaining deionized water to dilute, and then add N,N-dimethylethanolamine to adjust the pH to 6-8. Stir for 20-40 minutes and filter to obtain the product.

[0014] Furthermore, in step 101, the rotation speed during high-speed dispersion is 200-500 rpm.

[0015] Furthermore, in step 104, after the shell layer mixed monomers are dripped, the mixture is kept warm for 5 minutes, and then the initiator aqueous solution prepared in step S103 is dripped.

[0016] Furthermore, in step 105, filtration is performed using a 300-mesh nylon filter.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] The present invention solves the water resistance problem of the emulsion by introducing a certain amount of lauric methacrylate, a long-chain monomer with 12 or more carbon atoms, into the core monomer. This allows for a large amount of carboxylic acid in the shell, thus achieving controllable thixotropy without affecting water resistance. Furthermore, a reactive anionic emulsifier is used, and the shell monomer is added dropwise without pre-emulsification. The monomer is then bonded to the surface of the core layer of the latex particles through free radical polymerization, thus controlling the gel fraction. Furthermore, without the obstruction of the shell emulsifier, the organic amine can directly contact the carboxylic acid, shortening the time required for thickening after neutralization. DETAILED DESCRIPTION

[0019] The present invention will be further described in detail below with reference to specific embodiments.

[0020] A high-resistance and thixotropic emulsion with a core-shell structure is prepared by comprising the following components in parts by weight: 60-80 parts of deionized water, 0.3-2.5 parts of a reactive anionic emulsifier, 10-20 parts of butyl acrylate, 40-60 parts of methyl methacrylate, 1-2 parts of hydroxyethyl methacrylate, 0.5-2 parts of lauric methacrylate, 10-20 parts of methacrylic acid, 0.1-1 part of an initiator, and 1-5 parts of N,N-dimethylethanolamine.

[0021] Preferably, the reactive anionic emulsifier is HANERCHEM ® DNS-458, HANERCHEM ® The initiator is any one of DNS-86, Japan Aidico SR-10 and American Cytec AEROSOL MA-80, and the initiator is any one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0022] Example 1

[0023] S101. 10 parts of deionized water were added to container A, 0.2 parts of emulsifier SR-10 were added under stirring conditions, and after high-speed dispersion at 200 rpm for 20 minutes, 8 parts of butyl acrylate, 30 parts of methyl methacrylate, 0.8 parts of hydroxyethyl methacrylate and 0.5 parts of lauryl methacrylate were added, and high-speed dispersion was continued for 20 minutes to obtain a core layer pre-emulsion;

[0024] S102. Under stirring conditions, 29 parts of deionized water and 0.1 parts of emulsifier SR-10 were added to container B, the temperature was raised to 85°C, 0.05 parts of initiator potassium persulfate was added, and after the initiator was added, the core layer pre-emulsion prepared in step S101 was added dropwise to container B. The addition time was controlled within 1 hour. After the addition was completed, the temperature was kept for 1 hour.

[0025] S103 was added to container C 3 parts of butyl acrylate, 10 parts of methyl methacrylate, 0.2 parts of hydroxyethyl methacrylate and 10 parts of methacrylic acid, stirred for 5min to obtain a shell monomer mixture; to container D were added 1 part of deionized water and 0.05 parts of an initiator potassium persulfate, stirred to obtain an initiator aqueous solution;

[0026] S104. After the insulation of container B in step S102 is completed, the temperature is lowered to 70°C and the shell monomer mixture prepared in step S103 is added dropwise over 15 minutes. After the addition is complete, the temperature is kept for 5 minutes. The initiator aqueous solution prepared in step S103 is added dropwise over 10 minutes. After the addition is complete, the temperature is kept for 2 hours.

[0027] S105. After the insulation is completed, cool to below 50°C, add 20 parts of deionized water to dilute, and then add 1 part of N,N-dimethylethanolamine to adjust the pH to 6. Stir for 20 minutes, and filter through a 300-mesh nylon filter to obtain emulsion R-1.

[0028] Example 2

[0029] S201. 10 parts of deionized water were added to container A, 0.5 parts of emulsifier DNS-458 was added under stirring, and after high-speed dispersion at 300 rpm for 30 min, 15 parts of butyl acrylate, 40 parts of methyl methacrylate, 1 part of hydroxyethyl methacrylate and 2 parts of lauryl methacrylate were added, and high-speed dispersion was continued for 30 min to obtain a core layer pre-emulsion;

[0030] S202. Under stirring, 30 parts of deionized water and 1.2 parts of emulsifier DNS-458 were added to container B. The temperature was raised to 90°C, and 0.7 parts of initiator ammonium persulfate was added. After the initiator was added, the core layer pre-emulsion prepared in step S201 was added dropwise to container B. The addition time was controlled within 1 hour. After the addition was completed, the mixture was incubated for 1 hour.

[0031] S203. To container C were added 5 parts of butyl acrylate, 15 parts of methyl methacrylate, 0.5 parts of hydroxyethyl methacrylate and 15 parts of methacrylic acid, and stirred for 5 min to obtain a shell monomer mixture; to container D were added 1 part of deionized water and 0.3 parts of initiator ammonium persulfate, and stirred to obtain an initiator aqueous solution;

[0032] S204. After the insulation of container B in step S202 is completed, the temperature is lowered to 70°C and the shell monomer mixture prepared in step S203 is added dropwise over 15 minutes. After the addition is complete, the mixture is incubated for 5 minutes. The initiator aqueous solution prepared in step S203 is added dropwise over 10 minutes. The mixture is incubated for 2 hours.

[0033] S205. After the insulation is completed, cool to below 50°C, add 20 parts of deionized water to dilute, and then add 2 parts of N,N-dimethylethanolamine to adjust the pH to 6.5. Stir for 30 minutes, and filter through a 300-mesh nylon filter to obtain emulsion R-2.

[0034] Example 3

[0035] S301. 15 parts of deionized water were added to container A, 0.6 parts of emulsifier DNS-458 were added under stirring, and high-speed dispersion was performed at 300 rpm for 30 minutes. Then, 14 parts of butyl acrylate, 35 parts of methyl methacrylate, 1 part of hydroxyethyl methacrylate and 1.5 parts of lauryl methacrylate were added, and high-speed dispersion was continued for 30 minutes to obtain a core layer pre-emulsion.

[0036] S302. Under stirring, 30 parts of deionized water and 1.3 parts of emulsifier DNS-458 were added to container B. The temperature was raised to 90°C, and 0.5 parts of initiator ammonium persulfate was added. After the initiator was added, the core layer pre-emulsion prepared in step S301 was added dropwise to container B. The addition time was controlled to 1 hour. After the addition was completed, the temperature was kept for 1 hour.

[0037] S303. To container C were added 4 parts of butyl acrylate, 12 parts of methyl methacrylate, 0.5 parts of hydroxyethyl methacrylate and 15 parts of methacrylic acid, and stirred for 5 min to obtain a shell monomer mixture; to container D were added 1 part of deionized water and 0.2 parts of initiator ammonium persulfate, and stirred to obtain an initiator aqueous solution;

[0038] S304. After the insulation of container B in step S302 is completed, the temperature is lowered to 75°C and the shell monomer mixture prepared in step S303 is added dropwise over 15 minutes. After the addition is complete, the temperature is kept for 5 minutes. The initiator aqueous solution prepared in step S303 is added dropwise over 10 minutes. After the addition is complete, the temperature is kept for 2 hours.

[0039] S305. After the insulation is completed, cool to below 50°C, add 20 parts of deionized water to dilute, and then add 5 parts of N,N-dimethylethanolamine to adjust the pH to 8. Stir for 30 minutes and filter through a 300-mesh nylon filter to obtain emulsion R-3.

[0040] Example 4

[0041] S401. 15 parts of deionized water were added to container A, 0.8 parts of emulsifier DNS-86 was added under stirring, and after high-speed dispersion at 400 rpm for 20 minutes, 15 parts of butyl acrylate, 40 parts of methyl methacrylate, 1.1 parts of hydroxyethyl methacrylate and 1.8 parts of lauryl methacrylate were added, and high-speed dispersion was continued for 30 minutes to obtain a core layer pre-emulsion;

[0042] S402. Under stirring, 35 parts of deionized water and 1.7 parts of emulsifier DNS-86 were added to container B, the temperature was raised to 90°C, and 0.7 parts of initiator sodium persulfate was added. After the initiator was added, the core layer pre-emulsion prepared in step S401 was added dropwise to container B. The addition time was controlled within 1 hour. After the addition was completed, the temperature was kept for 1 hour.

[0043] S403. To container C were added 5 parts of butyl acrylate, 20 parts of methyl methacrylate, 0.5 parts of hydroxyethyl methacrylate and 20 parts of methacrylic acid, and stirred for 5 min to obtain a shell monomer mixture; to container D were added 2 parts of deionized water and 0.3 parts of an initiator, sodium persulfate, and stirred to obtain an initiator aqueous solution;

[0044] S404. After the insulation of container B in step S402 is completed, the temperature is lowered to 75°C and the shell monomer mixture prepared in step S403 is added dropwise over 15 minutes. After the addition is complete, the mixture is incubated for 5 minutes. The initiator aqueous solution prepared in step S403 is added dropwise over 10 minutes. The mixture is incubated for 2 hours.

[0045] S405. After the insulation is completed, cool to below 50°C, add 20 parts of deionized water to dilute, and then add 4 parts of N,N-dimethylethanolamine to adjust the pH to 7.5. Stir for 30 minutes, and filter through a 300-mesh nylon filter to obtain emulsion R-4.

[0046] Example 5

[0047] S501 was added to the container A 15 parts of deionized water, added 0.8 parts of emulsifier MA-80 under stirring conditions, 500rpm high-speed dispersion for 30min, then added 15 parts of butyl acrylate, 42 parts of methyl methacrylate, 1.2 parts of hydroxyethyl methacrylate and 2 parts of lauryl methacrylate, continued high-speed dispersion for 30min to obtain a core layer pre-emulsion;

[0048] S502. Under stirring, 38 parts of deionized water and 1.5 parts of emulsifier MA-80 were added to container B, the temperature was raised to 90°C, 0.6 parts of initiator ammonium persulfate was added, and after the initiator was added, the core layer pre-emulsion prepared in step S501 was added dropwise to container B. The addition time was controlled within 2 hours. After the addition was completed, the mixture was incubated for 1 hour.

[0049] S503. To container C were added 5 parts of butyl acrylate, 15 parts of methyl methacrylate, 0.8 parts of hydroxyethyl methacrylate and 18 parts of methacrylic acid, and stirred for 5 min to obtain a shell monomer mixture; to container D were added 2 parts of deionized water and 0.4 parts of initiator ammonium persulfate, and stirred to obtain an initiator aqueous solution;

[0050] S504. After the insulation of container B in step S502 is completed, the temperature is lowered to 70°C and the shell monomer mixture prepared in step S503 is added dropwise over 15 minutes. After the addition is complete, the temperature is kept for 5 minutes. The initiator aqueous solution prepared in step S503 is added dropwise over 10 minutes. After the addition is complete, the temperature is kept for 2 hours.

[0051] S505. After the insulation is completed, cool to below 50°C, add 25 parts of deionized water to dilute, and then add 3 parts of N,N-dimethylethanolamine to adjust the pH to 7. Stir for 30 minutes, and filter through a 300-mesh nylon filter to obtain emulsion R-5.

[0052] Comparative Example 1

[0053] Add 10 parts of deionized water to four-necked flask A and start stirring. Then, add 0.5 parts of emulsifier DNS-458. After high-speed dispersion at 300 rpm for 30 minutes, add 17 parts of butyl acrylate, 40 parts of methyl methacrylate, and 1 part of hydroxyethyl methacrylate. Continue high-speed dispersion for 30 minutes to form a viscous core layer pre-emulsion. Add 30 parts of deionized water and 1.2 parts of emulsifier DNS-458 to four-necked flask B. Heat the temperature to 90°C and add 0.7 parts of initiator ammonium persulfate. After the initiator is added, begin adding the core layer pre-emulsion dropwise over a 1-hour period. After the addition is complete, incubate for 1 hour. Add 5 parts of butyl acrylate, 15 parts of methyl methacrylate, 0.5 parts of hydroxyethyl methacrylate, and 15 parts of methacrylic acid to four-necked flask C. Stir for 5 minutes to form a shell layer monomer mixture. Add 1 part deionized water and 0.3 parts initiator ammonium persulfate to four-necked flask D and stir to prepare an initiator aqueous solution. After the four-necked flask B is insulated, cool it to 70°C and add the shell layer mixed monomer dropwise over 15 minutes. After the insulation, insulate for 5 minutes. After the insulation, add the initiator aqueous solution dropwise over 10 minutes. After the insulation, insulate for 2 hours. After the insulation, cool it to below 50°C, add 20 parts deionized water and 2 parts N,N-dimethylethanolamine to adjust the temperature. Stir for 30 minutes and filter through a 300-mesh nylon filter to obtain emulsion D-1.

[0054] Comparative Example 2

[0055] Add 10 parts of deionized water to four-necked flask A and start stirring. Then, add 0.5 parts of emulsifier DNS-458. After high-speed dispersion at 300 rpm for 30 minutes, add monomers 15 parts of butyl acrylate, 40 parts of methyl methacrylate, 1 part of hydroxyethyl methacrylate, and 2 parts of lauryl methacrylate. Continue high-speed dispersion for 30 minutes to form a viscous core layer pre-emulsion. Add 30 parts of deionized water and 0.8 parts of emulsifier DNS-458 to four-necked flask B. Heat the temperature to 90°C and add 0.7 parts of initiator ammonium persulfate. After the initiator is added, begin adding the core layer pre-emulsion dropwise over a period of 1 hour. After the addition is complete, keep the temperature incubated for 1 hour. To four-necked flask C, add 5 parts of deionized water, 0.2 parts of emulsifier DNS-458, 5 parts of butyl acrylate, 15 parts of methyl methacrylate, 0.5 parts of hydroxyethyl methacrylate, and 15 parts of methacrylic acid. Continue high-speed dispersion for 30 minutes to form a viscous shell pre-emulsion. To four-necked flask D, add 1 part of deionized water and 0.3 parts of initiator ammonium persulfate and stir to prepare an initiator aqueous solution. After the four-necked flask B is insulated, cool it to 70°C and add the shell pre-emulsion dropwise over 15 minutes. The mixture is then insulated for 5 minutes. The initiator aqueous solution is then added dropwise over 10 minutes. The mixture is then insulated for 2 hours. After the insulation is complete, cool it to below 50°C, add 15 parts of water and adjust the mixture with 2 parts of N,N-dimethylethanolamine. Stir for 30 minutes and filter through a 300-mesh nylon filter to obtain emulsion D-2.

[0056] Silver powder paints were prepared according to the following formulas using emulsions R-1 to R-5 prepared in Examples 1-5 and emulsions D-1 to D-2 prepared in Comparative Examples 1-2, respectively, to obtain silver powder paints Q-1 to Q-7. After thixotropy testing of Q-1 to Q-7, the prepared silver powder paints were evenly sprayed on tinplates with a spray gun, baked at 150° C. for 20 min, and then taken out and tested again to obtain the following Table 1.

[0057] Silver powder paint formula: 25 parts of silver powder paste, 0.2 parts of N,N-dimethylethanolamine, 1 part of ethylene glycol butyl ether, 1 part of dipropylene glycol methyl ether, 50 parts of emulsion, 0.3 parts of defoaming agent, and 0.3 parts of wetting and dispersing agent.

[0058] Table 1 Test data of silver powder paint Q-1~Q-7

[0059]

[0060] Conclusion analysis:

[0061] The emulsions R-1 to R-5 used in Q-1 to Q-5 were added with different amounts of dimethylethanolamine to achieve controllable thixotropy;

[0062] The emulsion D-1 used in Q-6 did not contain long-chain monomers, and the water resistance of the paint film was significantly deteriorated;

[0063] In the emulsion D-2 used in Q-7, the shell layer adopts a pre-emulsification process, the thixotropic index changes greatly with time, and the thixotropy is not as good as Q-1~Q-5.

[0064] The present invention solves the water resistance problem of the emulsion by introducing a certain amount of lauric methacrylate, a long-chain monomer with 12 or more carbon atoms, into the core monomer. This allows for a large amount of carboxylic acid in the shell, thus achieving controllable thixotropy without affecting water resistance. Furthermore, a reactive anionic emulsifier is used, and the shell monomer is added dropwise without pre-emulsification. The monomer is then bonded to the surface of the core layer of the latex particles through free radical polymerization, thus controlling the gel fraction. Furthermore, without the obstruction of the shell emulsifier, the organic amine can directly contact the carboxylic acid, shortening the time required for thickening after neutralization.

[0065] Those skilled in the art can make various other corresponding changes and deformations based on the technical solutions and concepts described above, and all of these changes and deformations should fall within the scope of protection of the claims of the present invention.

Claims

1. A highly resistant and thixotropic emulsion having a core-shell structure, characterized in that: The invention is prepared from the following components in parts by weight: 60-80 parts of deionized water, 0.3-2.5 parts of anionic emulsifier, 10-20 parts of butyl acrylate, 40-60 parts of methyl methacrylate, 1-2 parts of hydroxyethyl methacrylate, 0.5-2 parts of lauric methacrylate, 10-20 parts of methacrylic acid, 0.1-1 parts of initiator, and 1-5 parts of N,N-dimethylethanolamine. The anionic emulsifier is any one of DNS-458, SR-10, DNS-86 and MA-80; The preparation steps of a highly resistant and thixotropic emulsion with a core-shell structure are as follows: S101. Add part of deionized water to container A, add part of the emulsifier under stirring conditions, disperse at high speed for 20-40 minutes, then add part of butyl acrylate, part of methyl methacrylate, part of hydroxyethyl methacrylate and all of lauryl methacrylate, and continue to disperse at high speed for 20-40 minutes to obtain a core layer pre-emulsion; S102. Under stirring conditions, add part of the deionized water and the remaining emulsifier to container B, raise the temperature to 85-90 ° C, add part of the initiator, and after the initiator is added, add the core layer pre-emulsion prepared in step S101 dropwise to container B. The addition time is controlled within 1-2 hours. After the addition is completed, keep warm for 1 hour; S103. To container C were added the remaining butyl acrylate, the remaining methyl methacrylate, the remaining hydroxyethyl methacrylate and all methacrylic acid, and stirred for 5 min to obtain a shell monomer mixture; to container D were added a portion of deionized water and the remaining initiator, and stirred to obtain an initiator aqueous solution; S104. After the insulation of container B in step S102 is completed, the temperature is lowered to 70-75°C and the shell mixed monomer prepared in step S103 is added dropwise over 15 minutes. After the addition is complete, the initiator aqueous solution prepared in step S103 is added dropwise over 5-10 minutes. The mixture is then incubated for 2 hours. S105. After the insulation is completed, the temperature is lowered to below 50°C, and the remaining deionized water is added to dilute it. Then, N,N-dimethylethanolamine is added to adjust the pH to 6-8, and the mixture is stirred for 20-40 minutes. The mixture is filtered to obtain the product.

2. The emulsion according to claim 1, wherein The initiator is any one of ammonium persulfate, potassium persulfate and sodium persulfate.

3. The emulsion according to claim 1, wherein In step 101, the rotation speed during high-speed dispersion is 200-500 rpm.

4. The emulsion according to claim 1, wherein In step 104, after the shell layer mixed monomers are dripped, the mixture is kept warm for 5 minutes, and then the initiator aqueous solution prepared in step S103 is dripped.

5. The emulsion according to claim 1, wherein In step 105, filtering is performed using a 300-mesh nylon filter.

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