Water-based acrylic emulsion as well as preparation method and application thereof

Abstract

The invention provides a water-based acrylic emulsion as well as a preparation method and application thereof. The water-based acrylic emulsion comprises the following raw materials as polymerization units in parts by weight: 50-60 parts of a hard monomer; 35-45 parts of a soft monomer; 1-10 parts of an acid monomer; and 1-5 parts of a functional monomer. The water-based acrylic emulsion provided by the invention is of a single-phase structure and is relatively low in cost, the water resistance and the salt spray resistance after film formation can be greatly improved by introducing the coalescing agent and the functional monomer containing the modified glycidyl tertiary carboxylic ester into the formula, and the water-based acrylic emulsion is relatively low in free monomer content and meets the national environmental protection requirement. The invention also provides a water-based coating composition containing the water-based acrylic emulsion, and the water-based coating composition has the advantages of low cost and good corrosion resistance, so that the water-based coating composition has higher application and popularization values.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and specifically comprises a water-based acrylic emulsion and a preparation method and application thereof. Background Art

[0002] In recent years, with the increasingly stringent national environmental protection policies, water-based paints have gradually become a research hotspot in the current coatings industry due to their advantages such as non-toxicity, non-flammability, environmental friendliness, and energy saving. DTM coatings refer to anti-corrosion coatings that can be directly attached to metal surfaces, while the coatings used for traditional metal substrates are generally multi-coating systems, which at least require primer spraying and topcoat spraying steps. The formed primer layer provides adhesion and primary corrosion protection, and the topcoat layer provides weather resistance and UV protection, as well as aesthetic characteristics such as color and gloss. The resin used in the primer is usually epoxy resin, and the resin used in the topcoat is usually polyurethane. Therefore, when developing the coating, it is necessary to develop the coating formulas of the primer and topcoat separately, and two spraying processes are required during actual spraying, which greatly delays the development progress of the anti-corrosion coating. Prior art reports state that DTM coatings can replace the traditional multi-coating system to a certain extent, so that the coating has the functions of both primer and topcoat, thereby greatly improving production efficiency and saving costs.

[0003] At present, the commonly used DTM coatings are mainly divided into three categories: alkyd type, polyurethane type and acrylic emulsion type. For example, alkyd type DTM coatings are usually the cheapest and their performance is relatively low. Chinese patent CN 113773744 A discloses a method for preparing a water-based alkyd anticorrosive coating. The invention improves the salt spray resistance, hardness and aging resistance of the coating by introducing an isocyanate curing agent into the coating formula. However, the anticorrosive coating is a two-component coating with a short activation period, which is not conducive to construction application. The introduction of an isocyanate curing agent will also greatly increase the cost, which will lead to a lower cost performance of the coating and difficulty in promoting it in the market. Polyurethane type DTM coatings have the characteristics of high hardness and good chemical resistance, but the price is usually the highest among the three types of coatings, and its performance is relatively the best. Chinese patent CN 108129967 A discloses a method for preparing a water-based polyurethane anticorrosive coating. The invention adds nano-modified water-based polyurethane to the coating, so that the coating has a lower VOC, and the alkali and acid resistance and anticorrosion ability are enhanced.

[0004] The third type of acrylic emulsion type DTM coating is moderately priced, has relatively low VOC, has very excellent weather resistance, and is suitable for the protection of general indoor and outdoor metal substrates. Chinese patent CN 105859936 A discloses an acrylic copolymer emulsion and a water-based industrial anticorrosive paint with it as a film-forming material. The invention prepares the emulsion by a reactive emulsifier and a room temperature self-crosslinking technology, and removes residual monomers by oxidation-reduction, so that the coating prepared by the emulsion has good water whitening resistance, salt spray resistance and low VOC, but the composition of the emulsion is relatively complex, the synthesis process is relatively cumbersome, and the use of a self-crosslinking system and a reactive emulsifier greatly improves the cost of the emulsion, and the cost performance will be affected. At present, the emulsion that can be used to prepare acrylic emulsion type coatings usually adds special monomers such as phosphate monomers, acrylic cycloalkanoate monomers or urea monomers to improve the anticorrosion performance of the coating, but the price of such special monomers is high, and the cost performance is low, which is not conducive to the promotion and application of acrylic emulsion type coatings in the market. Summary of the invention

[0005] In view of the above problems existing in the prior art, the first object of the present invention is to provide a water-based acrylic emulsion that can be used to prepare DTM coatings. Compared with traditional water-based acrylic emulsions, the water-based acrylic emulsion provided by the present invention has the advantages of high hardness, low cost, low free monomer content, good film-forming property, etc., and the synthesis process is simple. When used in the preparation of DTM coatings, it is beneficial to improve the performance of DTM coatings in terms of corrosion resistance, hardness, water resistance, weather resistance, construction applicability, etc., and has high application and promotion value.

[0006] The second object of the present invention is to provide a method for preparing the aqueous acrylic emulsion as described above.

[0007] The third object of the present invention is to provide a DTM coating comprising the aqueous acrylic emulsion as described above.

[0008] A fourth object of the present invention is to provide a method for using the DTM coating as described above in the corrosion protection of metal, alloy and plastic substrates.

[0009] To achieve the above first object, the technical solution adopted by the present invention includes:

[0010] The present invention discloses an aqueous acrylic emulsion, which comprises the following raw materials as polymerization units in parts by weight:

[0011] 50-60 parts of hard monomer;

[0012] Soft monomer 35-45 parts;

[0013] 1-10 parts of acid monomer;

[0014] 1-5 copies of functional monomer;

[0015] The general structural formula of the functional monomer is shown in Formula I below:

[0016]

[0017] R1 and R2 are each independently selected from a C1-C6 alkyl group, and the total number of carbon atoms of R1 and R2 is 7;

[0018] The R3 is selected from any one of H and C1-C6 alkyl;

[0019] The aqueous acrylic emulsion further comprises 1 to 5 parts of a film-forming aid.

[0020] Furthermore, the film-forming aid includes but is not limited to one or more of propylene glycol butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, propylene glycol methyl ether acetate, diisobutyl adipate, dipropylene glycol methyl ether, dimethyl phthalate, dipropylene glycol butyl ether, dicyclopentenyloxyethyl acrylate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate (C-12), 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, dipropylene glycol dibenzoate, and dimethyl phthalate.

[0021] Furthermore, the aqueous acrylic emulsion contains 1-3 parts of a film-forming aid by weight.

[0022] Furthermore, the functional monomer is selected from one or more compounds having the following structures:

[0023]

[0024] Furthermore, the hard monomer includes, but is not limited to, one or more of styrene, methyl acrylate, methyl methacrylate, isobornyl acrylate, isobornyl methacrylate, acrylonitrile, cyclohexyl methacrylate, acrylamide, methacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide.

[0025] Further, the soft monomer includes but is not limited to one or more of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate, butyl acrylate, lauryl acrylate, lauryl methacrylate, vinyl versatate, n-decyl methacrylate, isobutyl acrylate, stearic methacrylate, and isodecyl acrylate.

[0026] Further, the acid monomer includes but is not limited to one or more of acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, 2-carboxyethyl acrylate, sodium vinyl sulfonate, sodium styrene sulfonate and 2-acrylamido-2-methylpropane sulfonic acid.

[0027] To achieve the above second purpose, the technical solution adopted by the present invention includes:

[0028] The present invention discloses a method for preparing the aqueous acrylic emulsion as described above, wherein the aqueous acrylic emulsion is obtained by one-step emulsion polymerization in an aqueous medium; the specific steps are:

[0029] Add some water and emulsifier into container A, and heat to 78-85°C under the protection of nitrogen;

[0030] In container B, hard monomer, soft monomer, acid monomer, functional monomer, film-forming aid, part of water and emulsifier are mixed to obtain a pre-emulsion;

[0031] Add part of water and initiator into container C and mix them to obtain an initiator aqueous solution;

[0032] Take 5-10wt% of the pre-emulsion and add it to container A, add part of the initiator aqueous solution to obtain a seed emulsion; after stirring for 2-3 hours, drip the remaining pre-emulsion and the initiator aqueous solution into container A at the same time, and keep warm for 1-2 hours. After the reaction is completed, distill under reduced pressure, adjust the solid content and pH, and obtain the seed emulsion.

[0033] To achieve the third objective, the technical solution adopted by the present invention includes:

[0034] The present invention discloses a water-based coating composition comprising the aqueous acrylic emulsion as described above.

[0035] To achieve the fourth objective, the technical solution adopted by the present invention includes:

[0036] The present invention discloses an application of the water-based coating composition described above in the corrosion protection of metal, alloy and plastic substrates.

[0037] Beneficial effects of the present invention:

[0038] The invention discloses a water-based acrylic emulsion. A hard monomer, a soft monomer and an acid monomer with relatively low cost are selected to reduce the production cost of the water-based acrylic emulsion. At the same time, in order to ensure the excellent emulsion performance, a film-forming aid and a functional monomer containing modified tertiary carbonic acid glycidyl ester are added thereto, mainly to improve the film-forming property thereof, so that a DTM coating prepared therefrom has excellent corrosion resistance, hardness, water resistance, weather resistance and construction applicability, and has performance equivalent to that of a disclosed acrylic emulsion type DTM coating, and has a high cost-performance ratio. Therefore, the water-based acrylic emulsion and the DTM coating containing the same have broad application prospects and commercial value. DETAILED DESCRIPTION

[0039] In order to explain the present invention more clearly, the present invention is further described below in conjunction with preferred embodiments. It should be clear that the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0040] In the case of illustrating and explaining the purpose of the present invention through the following examples, the components of the composition are explained in parts by weight as a general standard. Unless otherwise specified, for the sake of simplicity, the "parts" described in the examples of the present invention have the same meaning as parts by weight.

[0041] In view of the problem of low cost performance of acrylic emulsion used in preparing acrylic emulsion type DTM coating in the prior art, the present invention aims to develop a water-based acrylic emulsion with excellent performance and low cost. To this end, the inventor first selected some low-cost monomers as polymerization units from the perspective of cost, such as hard monomers such as styrene, soft monomers such as butyl methacrylate, and acid monomers such as methacrylic acid. However, due to their relatively low performance, it is difficult to meet application requirements. Subsequently, in order to improve the comprehensive performance of acrylic emulsion and make up for the disadvantage of poor performance of the above-mentioned monomers, the inventor tried to introduce a new type of monomer to improve the performance, and developed a functional monomer containing modified tert-butyl carbonate, the general structural formula of which is shown in the following formula I:

[0042]

[0043] R1 and R2 are each independently selected from a C1-C6 alkyl group, and the total number of carbon atoms of R1 and R2 is 7;

[0044] The R3 is selected from any one of H and C1-C6 alkyl.

[0045] Furthermore, the functional monomer is selected from at least one of the structures shown below:

[0046]

[0047] Furthermore, the aqueous acrylic emulsion contains 1-5 parts of functional monomers as polymerization units by weight.

[0048] The two monomers M1 and M2 provided by the present invention can be prepared by self-synthesis, and the preparation process is to prepare them by ring-opening of carboxyl-containing monomers and tert-butyl glycidyl carbonate. The carboxyl-containing monomers herein are preferably methacrylic acid and acrylic acid. In a specific embodiment, the present invention provides a typical preparation process, and the steps are as follows:

[0049] Add 228.37 parts by mass of tert-butyl glycidyl ester (Hansen Cardura) into the reaction vessel. TM E10P (epoxy content of 4100-4250mmol / kg, viscosity of 7.13mPa.s at 25°C), 72.06 parts by mass of acrylic acid, and 0.3 parts by mass of p-hydroxyanisole are mixed evenly, and then a ring-opening reaction is carried out at 110°C. If the acid value of the sample to be tested is <2mgKOH / g, the reaction is completed to obtain a functional monomer M1. The acid value is tested according to GB / T 2895-2008. The technician can refer to the above process to prepare the functional monomer M2.

[0050] From the structural point of view, the modified tert-butyl glycidyl carbonate structure is introduced into one end of the functional monomer. Since the tert-butyl carbonate structure has extremely strong hydrophobicity and low Tg, the polymer containing tert-butyl carbonate improves the film-forming property, water resistance and salt spray resistance to a certain extent. However, it was later found that even if the functional monomer of a specific structure is introduced, the degree of improvement of the coating performance is still limited. In order to further improve the performance of acrylic emulsion, the inventor takes improving film-forming property as a breakthrough, draws on the experience of improving film-forming property in coatings, adds the commonly used film-forming aid in the coating formula into the synthesis process of water-based acrylic emulsion, and slowly adds the film-forming aid together with the monomer during the synthesis process, so that the film-forming aid can enter the latex particles more completely and play a more full role. If the film-forming aid is added in the preparation process of the coating, since most of the coatings contain dispersants, wetting agents and other surfactants, the film-forming aid cannot enter the latex particles well, and cannot fully play the role of reducing the minimum film-forming temperature of the emulsion.

[0051] Furthermore, the film-forming aid includes but is not limited to one or more of propylene glycol butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, propylene glycol methyl ether acetate, diisobutyl adipate, dipropylene glycol methyl ether, dimethyl phthalate, dipropylene glycol butyl ether, dicyclopentenyloxyethyl acrylate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, dipropylene glycol dibenzoate, and dimethyl phthalate.

[0052] Furthermore, the aqueous acrylic emulsion contains 1-5 parts of a film-forming aid by weight.

[0053] Furthermore, the aqueous acrylic emulsion contains 1-3 parts of a film-forming aid by weight.

[0054] Furthermore, the hard monomer refers to an acrylic monomer whose homopolymer Tg is higher than 25°C, including but not limited to one or more of styrene, methyl acrylate, methyl methacrylate, isobornyl acrylate, isobornyl methacrylate, acrylonitrile, cyclohexyl methacrylate, acrylamide, methacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide.

[0055] Further, the aqueous acrylic emulsion contains 50-60 parts of hard monomers as polymerization units by weight; illustratively, the weight portions thereof can be 50 parts, 51 parts, 52 parts, 53 parts, 54 parts, 55 parts, 56 parts, 57 parts, 58 parts, 59 parts, 60 parts, and the like.

[0056] Furthermore, the soft monomer refers to an acrylic monomer whose homopolymer Tg is less than 25°C, including but not limited to one or more of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate, butyl acrylate, lauryl acrylate, lauryl methacrylate, vinyl ester of versatic acid, n-decyl methacrylate, isobutyl acrylate, stearic methacrylate, and isodecyl acrylate.

[0057] Further, the aqueous acrylic emulsion contains 35-45 parts of soft monomers as polymerization units by weight; illustratively, the weight parts thereof can be 35 parts, 36 parts, 37 parts, 38 parts, 39 parts, 40 parts, 41 parts, 42 parts, 43 parts, 44 parts, 45 parts, and the like.

[0058] Further, the acid monomer includes but is not limited to one or more of acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, 2-carboxyethyl acrylate, sodium vinyl sulfonate, sodium styrene sulfonate and 2-acrylamido-2-methylpropane sulfonic acid.

[0059] Further, the aqueous acrylic emulsion contains 1-10 parts of acid monomers as polymerization units by weight; illustratively, the weight parts thereof can be 1 part, 2 parts, 3 parts, 4 parts, 5 parts, 6 parts, 7 parts, 8 parts, 9 parts, 10 parts, and the like.

[0060] The present invention also provides a method for preparing the aqueous acrylic emulsion as described above. In the method, the aqueous acrylic emulsion is obtained by a one-step emulsion polymerization method. The specific steps are:

[0061] Add some water and emulsifier into container A, and heat to 78-85°C under the protection of nitrogen;

[0062] In container B, hard monomer, soft monomer, acid monomer, functional monomer, film-forming aid, part of water and emulsifier are mixed to obtain a pre-emulsion;

[0063] Add part of water and initiator into container C and mix them to obtain an initiator aqueous solution;

[0064] Take 5-10wt% of the pre-emulsion and add it to container A, add part of the initiator aqueous solution to obtain a seed emulsion; after stirring for 2-3 hours, drip the remaining pre-emulsion and the initiator aqueous solution into container A at the same time, and keep warm for 1-2 hours. After the reaction is completed, distill under reduced pressure, adjust the solid content and pH, and obtain the seed emulsion.

[0065] Furthermore, the emulsifier includes but is not limited to one or more of sodium lauryl polyoxyethylene ether sulfate, ammonium dodecylbenzene sulfonate, sodium laurate, sodium dodecyl sulfate, alkyl ammonium phosphate, sodium alkyl polyoxyethylene ether sulfonate, fatty alcohol ether phosphate, alkyl polyoxyethylene ether sulfonate, sodium tributylphenol polyoxyethylene ether sulfonate, allyl alkyl alcohol polyoxyethylene ether ammonium sulfate, and allyl polyoxypropylene ether ammonium sulfate.

[0066] Further, the emulsifier is used in an amount of 0.4-6.0% of the total monomer mass. Exemplarily, the emulsifier is used in an amount of 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, 1.6%, 1.7%, 1.8%, 1.9%, 2%, 2.1%, 2.2%, 2.3%, 2.4%, 2.5%, 2.6%, 2.7%, 2.8%, 2.9%, 3%, 3.5%, 4%, 4.5%, 5%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.85%, 5.9%, 5.95%, 6% and the like of the total monomer mass.

[0067] Furthermore, the initiator is a free radical initiator conventionally used in the art, including but not limited to one or more of hydrogen peroxide, ammonium persulfate, potassium persulfate, sodium persulfate, and tert-butyl hydroperoxide. A reducing agent may also be added during the polymerization process to form a redox system with the initiator, and the reducing agent includes but is not limited to one or more of isoascorbic acid, ascorbic acid, sodium formaldehyde sulfoxylate, sodium sulfite, and sodium bisulfite.

[0068] Further, the initiator is used in an amount of 0.2-1.5% of the total monomer mass. Exemplarily, the initiator is used in an amount of 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5% of the total monomer mass, etc.

[0069] Furthermore, deionized water and a neutralizing agent are used to adjust the solid content and pH to meet application requirements, and finally the solid content of the aqueous acrylic emulsion is controlled to be between 35% and 55%, and the pH is controlled to be between 7 and 9.

[0070] Furthermore, the neutralizing agent includes but is not limited to one or more of ammonia water, triethylamine, triethanolamine, dimethylethanolamine, 2-methyl-2-aminopropanol, dimethylisopropanolamine, methyldiethanolamine, AMP-95, ethyldiisopropylamine, and diethylethanolamine.

[0071] Furthermore, the free monomer content of the water-based acrylic emulsion can be reduced by using a reduced pressure distillation method, and the VOC in the subsequent coating can be further reduced, so that the prepared coating meets the current national standards.

[0072] The following will further illustrate this through specific examples.

[0073] Example 1

[0074] Add 600 parts of deionized water and 15 parts of Rhodafac RS-610A25 into container A, and heat to 85°C under nitrogen protection;

[0075] 350 parts of deionized water, 50 parts of Rhodafac RS-610A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of 2-ethylhexyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, 33 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and 11 parts of functional monomer M1 were added to container B and mixed to obtain a pre-emulsion;

[0076] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0077] 8 wt% of the pre-emulsion and 50 wt% of the initiator aqueous solution are added to container A, and the mixture is stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution are added dropwise for 2 hours, and the pipeline is flushed with 40 parts of deionized water, and the mixture is stirred at a temperature of 1 hour. The mixture is cooled to 50° C., 17 parts of ammonia water are added, and the mixture is stirred for 10 minutes, and then the mixture is distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water are added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material is filtered to obtain the aqueous acrylic emulsion with simple synthesis process, high hardness and low film-forming temperature.

[0078] Example 2

[0079] Add 600 parts of deionized water and 15 parts of Rhodafac RS-710A25 into container A, and heat to 85°C under nitrogen protection;

[0080] 350 parts of deionized water, 50 parts of Rhodafac RS-710A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, 33 parts of dipropylene glycol dibenzoate, and 11 parts of functional monomer M1 were added to container B and mixed to obtain a pre-emulsion;

[0081] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0082] 8 wt% of the pre-emulsion and 50 wt% of the initiator aqueous solution are added to container A, and the mixture is stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution are added dropwise for 2 hours, and the pipeline is flushed with 40 parts of deionized water, and the mixture is stirred at a temperature of 1 hour. The mixture is cooled to 50° C., 17 parts of ammonia water are added, and the mixture is stirred for 10 minutes, and then the mixture is distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water are added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material is filtered to obtain the aqueous acrylic emulsion with simple synthesis process, high hardness and low film-forming temperature.

[0083] Example 3

[0084] Add 600 parts of deionized water and 15 parts of Dowfax 2A1 into container A, and heat to 85°C under nitrogen protection;

[0085] 350 parts of deionized water, 50 parts of Dowfax 2A1, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, 33 parts of dipropylene glycol butyl ether, and 11 parts of functional monomer M2 were added to container B and mixed to obtain a pre-emulsion;

[0086] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0087] 8 wt % of the pre-emulsion and 50 wt % of the initiator aqueous solution are added to container A, and the mixture is stirred for 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution are added dropwise for 2 hours, and the pipeline is flushed with 40 parts of deionized water, and the mixture is stirred for 1 hour. The mixture is cooled to 50° C., 17 parts of AMP-95 are added, and the mixture is stirred for 10 minutes, and then the mixture is distilled under reduced pressure for 2 hours. Finally, deionized water and AMP-95 are added as needed to adjust the solid content to 42% and the pH to 7-9, and the material is filtered to obtain the aqueous acrylic emulsion with simple synthesis process, high hardness and low film-forming temperature.

[0088] Example 4

[0089] Add 600 parts of deionized water and 15 parts of Rhodafac RS-610A25 into container A, and heat to 85°C under nitrogen protection;

[0090] 350 parts of deionized water, 50 parts of Rhodafac RS-610A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, 33 parts of propylene glycol butyl ether, and 11 parts of functional monomer M2 were added to container B and mixed to obtain a pre-emulsion;

[0091] In a container C, 4.5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0092] 8 wt % of the pre-emulsion and 50 wt % of the initiator aqueous solution are added to container A, and the mixture is stirred for 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution are added dropwise for 2 hours, and the pipeline is flushed with 40 parts of deionized water, and the mixture is stirred for 1 hour. The mixture is cooled to 50° C., 9 parts of AMP-95 are added, and the mixture is stirred for 10 minutes, and then the mixture is distilled under reduced pressure for 2 hours. Finally, deionized water and AMP-95 are added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material is filtered to obtain the aqueous acrylic emulsion with simple synthesis process, high hardness and low film-forming temperature.

[0093] Example 5

[0094] Add 600 parts of deionized water and 15 parts of Rhodafac RS-610A25 into container A, and heat to 85°C under nitrogen protection;

[0095] 350 parts of deionized water, 50 parts of Rhodafac RS-610A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, 33 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and 33 parts of functional monomer M1 were added to container B and mixed to obtain a pre-emulsion;

[0096] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0097] 8 wt% of the pre-emulsion and 50 wt% of the initiator aqueous solution are added to container A, and the mixture is stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution are added dropwise for 2 hours, and the pipeline is flushed with 40 parts of deionized water, and the mixture is stirred at a temperature of 1 hour. The mixture is cooled to 50° C., 17 parts of ammonia water are added, and the mixture is stirred for 10 minutes, and then the mixture is distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water are added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material is filtered to obtain the aqueous acrylic emulsion with simple synthesis process, high hardness and low film-forming temperature.

[0098] Example 6

[0099] Add 600 parts of deionized water and 15 parts of Rhodafac RS-710A25 into container A, and heat to 85°C under nitrogen protection;

[0100] 350 parts of deionized water, 50 parts of Rhodafac RS-710A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, 11 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, and 33 parts of functional monomer M1 were added to container B and mixed to obtain a pre-emulsion;

[0101] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0102] 8 wt% of the pre-emulsion and 50 wt% of the initiator aqueous solution are added to container A, and the mixture is stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution are added dropwise for 2 hours, and the pipeline is flushed with 40 parts of deionized water, and the mixture is stirred at a temperature of 1 hour. The mixture is cooled to 50° C., 17 parts of ammonia water are added, and the mixture is stirred for 10 minutes, and then the mixture is distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water are added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material is filtered to obtain the aqueous acrylic emulsion with simple synthesis process, high hardness and low film-forming temperature.

[0103] Comparative Example 1

[0104] Add 600 parts of deionized water and 15 parts of Rhodafac RS-610A25 into container A, and heat to 85°C under nitrogen protection;

[0105] 350 parts of deionized water, 50 parts of Rhodafac RS-610A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, and 11 parts of functional monomer M1 were added to container B and mixed to obtain a pre-emulsion;

[0106] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0107] 8 wt % of the pre-emulsion and 50 wt % of the initiator aqueous solution were added to container A, and the mixture was stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution were added dropwise for 2 hours, and the pipeline was flushed with 40 parts of deionized water, and the mixture was stirred at a temperature of 1 hour. The mixture was cooled to 50° C., 17 parts of ammonia water were added, and the mixture was stirred for 10 minutes, and then the mixture was distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water were added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material was filtered to obtain an aqueous acrylic emulsion.

[0108] Comparative Example 2

[0109] Add 600 parts of deionized water and 15 parts of Rhodafac RS-710A25 into container A, and heat to 85°C under nitrogen protection;

[0110] 350 parts of deionized water, 50 parts of Rhodafac RS-710A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, and 60 parts of methacrylic acid were added to container B and mixed to obtain a pre-emulsion;

[0111] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0112] 8 wt % of the pre-emulsion and 50 wt % of the initiator aqueous solution were added to container A, and the mixture was stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution were added dropwise for 2 hours, and the pipeline was flushed with 40 parts of deionized water, and the mixture was stirred at a temperature of 1 hour. The mixture was cooled to 50° C., 17 parts of ammonia water were added, and the mixture was stirred for 10 minutes, and then the mixture was distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water were added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material was filtered to obtain an aqueous acrylic emulsion.

[0113] Comparative Example 3

[0114] Add 600 parts of deionized water and 15 parts of Rhodafac RS-610A25 into container A, and heat to 85°C under nitrogen protection;

[0115] 350 parts of deionized water, 50 parts of Rhodafac RS-610A25, 450 parts of styrene, 160 parts of methyl methacrylate, 230 parts of isooctyl acrylate, 200 parts of butyl methacrylate, 60 parts of methacrylic acid, and 33 parts of 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate were added to container B and mixed to obtain a pre-emulsion;

[0116] In a container C, 5 parts of ammonium persulfate and 120 parts of deionized water are mixed to obtain an initiator aqueous solution;

[0117] 8 wt % of the pre-emulsion and 50 wt % of the initiator aqueous solution were added to container A, and the mixture was stirred at a temperature of 20 minutes to obtain a seed emulsion; then the remaining pre-emulsion and the initiator aqueous solution were added dropwise for 2 hours, and the pipeline was flushed with 40 parts of deionized water, and the mixture was stirred at a temperature of 1 hour. The mixture was cooled to 50° C., 17 parts of ammonia water were added, and the mixture was stirred for 10 minutes, and then the mixture was distilled under reduced pressure for 2 hours. Finally, deionized water and ammonia water were added as needed to adjust the solid content to 42% and the pH to between 7 and 9, and the material was filtered to obtain an aqueous acrylic emulsion.

[0118] Performance Testing

[0119] Solution 1: Use Examples 1-6 and Comparative Examples 1-3 as raw materials to prepare DTM white paint. The specific formula is shown in Table 1.

[0120] Table 1 DTM white paint formula

[0121]

[0122] The DTM white coating is prepared according to the following preparation process:

[0123] Add deionized water and BYK 190 into a dispersion tank and stir at 200 rpm, then add AMP-95, BYK-024 and Ti-Pure R-960 in turn, then increase the speed to 1500 rpm, stir until the fineness is less than 35 μm, reduce the speed to 800 rpm, add water-based acrylic emulsion, C-12, TEGO 4100, H10 and ACRYSOL RM-8W in turn to obtain DTM white coating.

[0124] Scheme 2: Using Comparative Example 1 as a raw material, a DTM white paint was prepared according to the formula in Table 2, which was recorded as Comparative Example 4. The difference between Scheme 1 and Scheme 2 lies in the change in the amount of C-12. The incremental change of C-12 in the DTM white paint formula of Scheme 2 is obtained by converting the difference between Example 1 and Comparative Example 1 in the DTM white paint, so as to ensure that the amount of film-forming aid in the DTM white paint obtained in Scheme 1 and Scheme 2 is the same.

[0125] Table 2 DTM white paint formula

[0126]

[0127] The DTM white coating is prepared according to the following preparation process:

[0128] Add deionized water and BYK 190 into a dispersion tank and stir at 200 rpm, then add AMP-95, BYK-024 and Ti-Pure R-960 in turn, then increase the speed to 1500 rpm, stir until the fineness is less than 35 μm, reduce the speed to 800 rpm, add water-based acrylic emulsion, C-12, TEGO 4100, H10 and ACRYSOL RM-8W in turn to obtain DTM white coating.

[0129] The salt spray resistance of the two DTM white coatings was tested by making plates according to the method in the national standard GB 1765. The water resistance of the two DTM white coatings was tested by making plates according to the method in the national standard GB / T 1733. The pencil hardness of the two DTM white coatings was tested according to the method in the national standard GB / T1732-1993. The minimum film-forming temperature of the water-based acrylic emulsion was tested according to GB / T9267-2008. The free monomer content of the water-based acrylic emulsion was tested by gas chromatography. The obtained performance test results are summarized in Table 3.

[0130] Table 3

[0131]

[0132]

[0133] As shown in Table 3, in the embodiments provided by the present invention, after the functional monomers and the film-forming aids are introduced, the prepared coating can have higher hardness, better water resistance and salt spray resistance, and low free monomer content, which is significantly improved compared to the traditional acrylic emulsion type DTM coating, and has met the application needs of DTM coatings in today's society. And by comparing the coating prepared with the acrylic emulsion of Example 1 as the raw material in Scheme 1 and the coating prepared with the acrylic emulsion of Comparative Example 1 as the raw material in Scheme 2, it is found that when part of the film-forming aid is introduced into the preparation of the acrylic emulsion, it is also beneficial to improve the performance of the DTM coating in terms of water resistance and salt spray resistance.

[0134] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not limitations on the implementation methods of the present invention. For ordinary technicians in the relevant field, other different forms of changes or modifications can be made based on the above description. It is impossible to list all the implementation methods here. All obvious changes or modifications derived from the technical solution of the present invention are still within the protection scope of the present invention.

Claims

1. A water-based acrylic emulsion, characterized in that: The aqueous acrylic emulsion comprises the following raw materials as polymerization units by weight: 50-60 parts of hard monomer; Soft monomer 35-45 parts; 1-10 parts of acid monomer; 1-5 copies of functional monomer; The general structural formula of the functional monomer is shown in Formula I below: R1 and R2 are each independently selected from a C1-C6 alkyl group, and the total number of carbon atoms of R1 and R2 is 7; The R3 is selected from any one of H and C1-C6 alkyl; The aqueous acrylic emulsion further comprises 1 to 5 parts of a film-forming aid.

2. The aqueous acrylic emulsion according to claim 1, characterized in that The film-forming aid is selected from one or more of propylene glycol butyl ether, tripropylene glycol n-butyl ether, propylene glycol phenyl ether, propylene glycol methyl ether acetate, diisobutyl adipate, dipropylene glycol methyl ether, dimethyl phthalate, dipropylene glycol butyl ether, dicyclopentenyloxyethyl acrylate, 2,2,4-trimethyl-1,3-pentanediol monoisobutyrate, 2,2,4-trimethyl-1,3-pentanediol diisobutyrate, dipropylene glycol dibenzoate, and dimethyl phthalate.

3. The aqueous acrylic emulsion according to claim 1, characterized in that The aqueous acrylic emulsion contains 1-3 parts of a film-forming aid by weight.

4. The aqueous acrylic emulsion according to claim 1, characterized in that The functional monomer is selected from one or more compounds with the following structures:

5. The aqueous acrylic emulsion according to claim 1, characterized in that The hard monomer is selected from one or more of styrene, methyl acrylate, methyl methacrylate, isobornyl acrylate, isobornyl methacrylate, acrylonitrile, cyclohexyl methacrylate, acrylamide, methacrylamide, N,N-dimethylacrylamide, and N-hydroxymethylacrylamide.

6. The aqueous acrylic emulsion according to claim 1, characterized in that The soft monomer is selected from one or more of 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, butyl methacrylate, tert-butyl methacrylate, tert-butyl acrylate, butyl acrylate, lauryl acrylate, lauryl methacrylate, vinyl ester of versatic acid, n-decyl methacrylate, isobutyl acrylate, stearic methacrylate, and isodecyl acrylate.

7. The aqueous acrylic emulsion according to claim 1, characterized in that The acid monomer is selected from one or more of acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid, fumaric acid, 2-carboxyethyl acrylate, sodium vinyl sulfonate, sodium styrene sulfonate and 2-acrylamido-2-methylpropane sulfonic acid.

8. The method for preparing the aqueous acrylic emulsion according to any one of claims 1 to 7, characterized in that: Obtaining the aqueous acrylic emulsion by one-step emulsion polymerization in an aqueous medium; The specific steps are: Add some water and emulsifier into container A, and heat to 78-85°C under the protection of nitrogen; In container B, hard monomer, soft monomer, acid monomer, functional monomer, film-forming aid, part of water and emulsifier are mixed to obtain a pre-emulsion; Add part of water and initiator into container C and mix them to obtain an initiator aqueous solution; Take 5-10wt% of the pre-emulsion and add it to container A, add part of the initiator aqueous solution to obtain a seed emulsion; after stirring for 2-3 hours, drip the remaining pre-emulsion and the initiator aqueous solution into container A at the same time, and keep warm for 1-2 hours. After the reaction is completed, distill under reduced pressure, adjust the solid content and pH, and obtain the seed emulsion.

9. A water-based coating composition, characterized in that: The aqueous acrylic emulsion comprises the aqueous acrylic emulsion according to any one of claims 1 to 7.

10. Use of the water-based coating composition as claimed in claim 9 in the corrosion protection of metal, alloy and plastic substrates.

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