Acrylic emulsion for building exterior wall coating and preparation method and application thereof

Abstract

The invention provides an acrylic ester emulsion for building exterior wall coatings and a preparation method and application thereof. The emulsion comprises the following components in parts by weight as raw materials: a) 15 to 35 parts by weight of a monovinyl aromatic monomer; b) 20 to 45 parts by weight of an alkyl (meth)acrylate; c) 0.5 to 5 parts by weight of a C-containing α,β-monoethylenically unsaturated bond; 3‑6 Monocarboxylic acid and C 3‑6 dicarboxylic acid; d) 0.5 to 5.0 parts by mass of a polymerizable benzophenone photoinitiator; e) 1.0 to 5.0 parts by mass of a monomer having a hydrolyzable Si-organic bond. The present invention also provides a method for preparing the above-mentioned emulsion, which is prepared by free radical emulsion polymerization of the above-mentioned components. The acrylate emulsion provided by the present invention or the acrylic emulsion prepared by the method of the present invention is used for elastic coatings for building exterior walls, and has excellent tensile strength, elongation at break, stain resistance and rain mark resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of building coatings, and relates to an acrylic ester elastic emulsion for building exterior wall coatings, and a preparation method and application thereof. Background Art

[0002] At present, most buildings in my country are plastered with cement mortar as the base. When the plaster mortar hardens, hardening cracks are generated due to volume reduction; when the temperature changes, temperature cracks are generated due to thermal expansion and contraction; when the dryness and wetness change, shrinkage cracks are generated due to wet expansion and dryness contraction; when freezing and thawing, freeze-thaw cracks are generated due to the volume expansion of water when it freezes; structural cracks are generated due to the settlement of the base layer, etc., which lead to cracking of the protective decorative coating, and rainwater seeps into the wall through the cracks, deepening the damage to the building, such as steel bar corrosion, which endangers the building.

[0003] Elastic architectural coatings refer to coatings that are made of synthetic resin emulsions as base materials, pigments, fillers and additives. After being applied to a certain thickness, they have the elastic function of covering the small cracks caused by the expansion (movement) of the substrate. Elastic architectural coatings are mainly used for exterior walls. The biggest difference between them and ordinary exterior wall architectural coatings is that the coating film of elastic coatings requires a certain elongation (the elongation at break is generally at least greater than 250%). This difference makes the glass transition temperature (Tg) of synthetic resin emulsions used in elastic coatings usually relatively low (<-15℃); at the same time, like other exterior wall coatings, elastic exterior wall coatings also require a certain degree of stain resistance. However, due to the low Tg of elastic emulsions, the paint film is relatively soft, and the coating is very easy to stick to dust after painting, which greatly affects the decorative effect of the coating.

[0004] In addition, when construction is carried out outdoors, due to the changeable weather, the differences in temperature and humidity are very obvious, especially in rainy seasons. The coating film is very likely to bloom, bubble, and fall off easily. Rain marks are also very common, and the rain marks greatly affect the appearance. Therefore, in order to maintain the appearance, it is likely that the paint will have to be repainted every few years. Moreover, the current buildings are relatively tall, which increases costs and wastes overall energy and resources, and also limits the application of elastic coatings.

[0005] In order to improve the stain resistance of exterior wall elastic coatings in the prior art, the above purpose is achieved mainly through the following methods: First, increase the amount of filler in the exterior wall elastic coating, so that the exterior wall elastic coating shows less elastic emulsion after drying and forming a film, which is not easy to stick to dust, or use fillers of smaller size, so that the exterior wall elastic coating is more dense and not easy to stick to dust. However, the obvious disadvantage of this method is that the elasticity of the exterior wall elastic coating drops sharply due to the increase of PVC, especially the low-temperature elasticity; second, increase the glass transition temperature (Tg), the surface viscosity and hardness of the coating depend on the Tg of the polymer, so the high or low Tg of the polymer in the coating is the most important factor affecting the stain resistance of the coating. However, the disadvantage of this method is that the elastic mechanical properties are seriously lost, especially the low-temperature elasticity, and the excellent mechanical properties of the elastic emulsion cannot be reflected; third, improve the compactness of the coating, improving the compactness of the coating is an important way to improve the stain resistance of the coating, and photoinitiators are often used in building exterior wall coatings to crosslink the surface of the polymer film to improve the stain resistance. Benzophenone is a typical representative of photoinitiators, which is particularly effective in improving stain resistance without affecting the mechanical properties of elastic coatings. Unfortunately, benzophenone has been identified as a possible human carcinogen; in addition, benzophenone is considered a volatile organic compound (VOC), and its adverse environmental impact is undesirable. This volatility has the additional disadvantage of causing changes in the crosslink density of the paint film, and the benzophenone will evaporate from the film before reacting at the surface of the paint film.

[0006] Therefore, developing an elastic emulsion for exterior walls, which can be used to prepare elastic coatings with excellent mechanical properties, stain resistance, no or slight rain marks, and environmental friendliness, will have very broad application prospects and social benefits. Summary of the invention

[0007] In order to overcome the deficiencies in the prior art, the present invention provides a new acrylic elastic emulsion for building exterior walls and a preparation method thereof, wherein a monoethylenically unsaturated monocarboxylic acid and a dicarboxylic acid are used simultaneously in the polymerization process, a polymerizable benzophenone photoinitiator is introduced, a monoethylenically unsaturated monocarboxylic acid is added in the late stage of polymerization, a hydrolyzable Si-organic bond monomer is added after the polymerization is completed, and the monomer is copolymerized with an acrylic ester monomer through free radical emulsion polymerization to obtain the acrylic elastic emulsion. The acrylic elastic emulsion provided by the present invention has excellent tensile strength, elongation at break, excellent stain resistance and rain mark resistance.

[0008] In order to achieve the purpose of the present invention, the present invention adopts the following technical solutions:

[0009] The first aspect of the present invention provides an acrylic emulsion for building exterior wall coatings, wherein the acrylic emulsion is prepared from the following components in parts by weight as raw materials:

[0010] a) 15 to 35 parts by mass of a monovinyl aromatic monomer, preferably 15 to 30 parts by mass;

[0011] b) 20 to 45 parts by mass of an alkyl (meth)acrylate, preferably 25 to 40 parts by mass;

[0012] c) 0.5 to 5 parts by mass of C containing α,β-monoethylenically unsaturated bonds 3-6 Monocarboxylic acid and C 3-6 Dicarboxylic acid, preferably 2.0 to 5.0 parts by mass;

[0013] d) 0.5 to 5.0 parts by weight of a polymerizable benzophenone photoinitiator, preferably 0.5 to 2.0 parts by weight;

[0014] e) 1.0 to 5.0 parts by mass of a monomer having a hydrolyzable Si-organic bond, preferably 1.5 to 3.5 parts by mass.

[0015] The acrylic ester elastic emulsion provided by the present invention is prepared by compounding a hard monomer-monovinyl aromatic monomer (i.e. component a)) with a soft monomer-(meth) alkyl acrylate (i.e. component b)), and adding a branched crosslinking monomer such as carboxylic acid (i.e. component c)). During copolymerization, a crosslinking reaction occurs so that the latex particles form a flexible long-chain crosslinked network with a low crosslinking degree, which ensures high elasticity and sufficient strength while having a certain rigidity.

[0016] In the acrylic ester emulsion provided by the present invention, in component c) C 3-6 The monocarboxylic acid is selected from one or more of acrylic acid, methacrylic acid, ethacrylic acid, allyl acetic acid, crotonic acid or vinyl acetic acid; preferably acrylic acid or methacrylic acid; the C 3-6 The dicarboxylic acid is selected from one or more of itaconic acid, fumaric acid, maleic acid or 2-methylmaleic acid; preferably itaconic acid.

[0017] The acrylic elastic emulsion provided by the present invention is a compound of monocarboxylic acid and dicarboxylic acid in component c), and the distribution form of carboxyl groups on the particle surface is changed by acids of different ionic strengths. Dicarboxylic acid can increase the charge density on the particle surface, while monocarboxylic acid can prevent excessive carboxylic acid density from affecting its distribution, thereby making the polymer surface layer have good hydrophilicity; monocarboxylic acid is added in the late stage of polymerization, and can also be further enriched on the polymer surface, which can effectively improve the wetting and dispersing ability of the emulsion on the color and filler, and can effectively prevent the rain mark problem caused by the migration of the wetting dispersant in the coating film. In addition, the surface layer of the paint film is appropriately hydrophilic, which can effectively prevent the generation of rain marks, and also well wet the dust so that the gray layer is easily washed away by rainwater, further improving its anti-fouling performance.

[0018] In the acrylic emulsion provided by the present invention, the polymerizable benzophenone photoinitiator in component d) has a structure shown in the following formula:

[0019]

[0020] Wherein, x is from 2 to 13, y is from 5 to 20, and x+y≤25; preferably, x is from 8 to 10, for example, 9; y is from 6 to 18, for example, 10, 16;

[0021] R is selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, sec-pentyl; preferably methyl or ethyl.

[0022] The raw materials of the acrylic ester elastic emulsion of the present invention introduce a polymerizable benzophenone photoinitiator, and the molecular structure thereof contains not only a photoactive group, but also an unsaturated double bond and a hydrophilic substance (PO-EO oligomer). The unsaturated double bond can be copolymerized with the acrylic ester monomer, so that the photoinitiator can be anchored in the polymer network, reducing the volatility and surface migration problems of conventional small molecule photoinitiators; the hydrophilic substance (PO-EO oligomer) can adjust the hydrophilicity and hydrophobicity of the compound, so that the compound migrates to the latex / water or water / air interface; after drying, the compound is preferentially located on the surface, and can effectively undergo ultraviolet light crosslinking after being irradiated with ultraviolet light for a certain period of time. The outermost surface of the coating film becomes dense and has a higher hardness due to the crosslinking effect, and the anti-fouling performance can be significantly improved.

[0023] In the acrylic emulsion provided by the present invention, the monovinyl aromatic monomer in the component a) is selected from styrene, 2-methylstyrene, 4-methylstyrene, 2-(n-butyl)styrene, 4-(n-butyl)styrene and / or 4-(n-decyl)styrene; preferably, the monovinyl aromatic monomer in the component a) is selected from styrene.

[0024] In the acrylic emulsion provided by the present invention, the (meth)acrylic acid alkyl ester in the component b) is selected from one or more of n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, n-hexyl methacrylate or 2-ethylhexyl methacrylate; preferably, the (meth)acrylic acid alkyl ester in the component b) is selected from methyl methacrylate, n-butyl acrylate and 2-ethylhexyl acrylate.

[0025] In the acrylic emulsion provided by the present invention, the monomer having a hydrolyzable Si-organic bond in the component e) is selected from one or more of γ-glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane or β-(3,4-epoxycyclohexyl)-ethyltriethoxysilane; preferably, the monomer having a hydrolyzable Si-organic bond in the component e) is selected from β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane or γ-glycidyloxypropyltrimethoxysilane; more preferably, it is γ-glycidyloxypropyltrimethoxysilane.

[0026] The second aspect of the present invention provides a method for preparing the acrylic emulsion for building exterior wall coatings, comprising the following steps:

[0027] 1) preparing a pre-emulsion: taking a portion of an emulsifier, 0.1-1.0 parts by weight of a multifunctional anionic monomer and 25-55 parts by weight of deionized water, adding the component a), component b), component d) and a portion of component c) thereto, mixing and setting aside;

[0028] 2) preparing the bottom liquid: adding the remaining emulsifier, 0.001-0.01 parts by weight of polymerization inhibitor and 30-60 parts by weight of deionized water into the reaction kettle, heating to 50-75° C. for standby use;

[0029] 3) preparing an oxidant solution: mixing 0.2-1.0 parts by weight of an oxidant, 0.1-1.0 parts by weight of a buffer and 3.5-10 parts by weight of deionized water for later use;

[0030] 4) preparing a reducing agent solution: mixing 0.3-1.5 parts by weight of a reducing agent and 5-15 parts by weight of deionized water for later use;

[0031] 5) at 50-75° C., add 1%-10% by weight of pre-emulsion, 10%-60% by weight of oxidant solution and 10%-60% by weight of reducing agent solution to the bottom liquid of the kettle in sequence, react for 10-30 minutes, and then dropwise add the remaining pre-emulsion, oxidant solution and reducing agent solution thereto; when 10%-25% of the pre-emulsion remains, stop dropping, add the remaining component c) thereto at one time, mix well, and continue to dropwise add the remaining pre-emulsion, oxidant solution and reducing agent solution, and ensure that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion during the continued dropping process; keep warm for 30-90 minutes after the dropping is completed;

[0032] 6) After adding the post-treatment agent dropwise into the reaction kettle, the temperature is lowered to 15-45° C., and then component e), a defoamer, and a bactericide are added thereto, and the pH is adjusted to 7.0-9.0, and the acrylic elastic emulsion is obtained after filtering.

[0033] In a specific embodiment of the preparation method of the present invention, based on the mass of the emulsifier being 100%, the emulsifier added in step 1) is 65-90%; the emulsifier is selected from fatty alcohol oxyethylene ether ammonium sulfate, and its molecular formula is RO (CH2CH2O) n -SO3NH4; preferably R is allyloxy, that is, preferably allyloxy fatty alcohol oxyethylene ether ammonium sulfate, wherein the number of ethylene oxide (abbreviated as "EO number") is 3-30, for example, 5, 10, 20.

[0034] In the preparation method of the acrylic elastic emulsion of the present invention, a reactive emulsifier is used for free radical polymerization, wherein the reactive emulsifier contains a double bond and can be free radical polymerized with the acrylic monomer, and gradually copolymerized and grafted onto the polymer particles, thereby avoiding the emulsifier migrating to the coating surface under the action of rain water, causing color changes and resulting in rain marks.

[0035] In the present invention, the multifunctional anionic monomer is selected from one or more of sodium vinyl sulfonate, sodium vinylbenzene sulfonate, sodium 3-allyloxy-1-hydroxy-propane sulfonate or sodium 2-acrylamide-2-methylpropane sulfonate, preferably sodium vinylbenzene sulfonate.

[0036] In step 1) of the method of the present invention, the added component c) comprises all of the C 3-6 dicarboxylic acid and a portion of the C 3-6 Monocarboxylic acid; in some preferred embodiments, C 3-6 The total mass of the monocarboxylic acid is 100%, and the C 3-6 Monocarboxylic acids are 50-80% and the remaining 20-50% is C 3-6 The monocarboxylic acid is added all at once in step 3).

[0037] In step 3) of the method of the present invention, the buffer is selected from one or more of sodium carbonate, sodium bicarbonate, sodium phosphate or sodium dihydrogen phosphate, preferably sodium bicarbonate; the oxidant is selected from water-soluble oxidants, including but not limited to at least one of ammonium persulfate, sodium persulfate, and potassium persulfate, more preferably ammonium persulfate.

[0038] In step 4) of the method of the present invention, the reducing agent is selected from one or more of sodium sulfite, sodium bisulfite or sodium pyrosulfite, preferably sodium pyrosulfite.

[0039] In a specific embodiment of step 5) of the method of the present invention, the total dripping time of the pre-emulsion is controlled at 180-300 minutes; in some preferred embodiments, the dripping time of the oxidant solution and the reducing agent solution is 5-20 minutes longer than the dripping time of the pre-emulsion. The present invention adopts a pre-emulsification semi-continuous dripping process, which effectively improves the stability of the polymerization and allows the chemical reaction to proceed under relatively mild conditions. For example, after the reaction in step 5) for 10-30 minutes, the first 1 / 3 of the pre-emulsion can be added by half-speed dripping, and the last 2 / 3 of the pre-emulsion can be added by full-speed dripping.

[0040] In step 6) of the method of the present invention, the time for dripping the post-treatment agent is 30-60 minutes, and the temperature is kept warm for 30-60 minutes after dripping; wherein the post-treatment agent includes but is not limited to at least one of tert-butyl hydroperoxide (T-BHP), tert-amyl hydroperoxide (T-AHP), sodium bisulfite, sodium dithionite and isoascorbic acid, preferably selected from tert-butyl hydroperoxide and / or isoascorbic acid, and more preferably a mixture of tert-butyl hydroperoxide and isoascorbic acid in a mass ratio of 2:1.

[0041] In some specific embodiments, in step 6), ammonia water is used as a pH adjuster to adjust the pH value of the system to 7.0-9.0.

[0042] The preparation method of the present invention adds a hydrolyzable silicone monomer (i.e., component e) after the polymerization is completed. The molecular structure of the hydrolyzable silicone monomer contains reactive glycidoxy and methoxy groups, which makes the adhesion between the powder and the emulsion stronger and the density of the paint film surface is greatly improved, which not only balances the elasticity and strength of the paint film, but also improves the stain resistance of the paint film.

[0043] The third aspect of the present invention provides a latex paint, comprising the above-mentioned acrylic emulsion or the acrylic emulsion obtained by the above-mentioned preparation method; the latex paint is preferably used in exterior wall elastic latex paint.

[0044] The above technical solution has the following technical effects:

[0045] In the acrylic elastic emulsion provided by the present invention, a hard monomer-monovinyl aromatic monomer (i.e., component a)) and a soft monomer-(meth) alkyl acrylate (i.e., component b)) are compounded, and a branched cross-linking monomer such as carboxylic acid (i.e., component c)) is added at the same time. During copolymerization, a cross-linking reaction occurs so that the latex particles form a flexible long-chain cross-linked network with a low cross-linking degree, which ensures high elasticity and sufficient strength while having a certain rigidity.

[0046] The method for preparing the acrylic elastic emulsion of the present invention adopts a low-temperature redox polymerization process, and the molecular weight of the polymer far exceeds the molecular weight of the elastic emulsion obtained by ordinary thermal initiation. In terms of mechanical properties, the elongation at break and the tensile strength are higher; at the same time, the preparation method of the present invention can effectively improve the wetting and dispersing ability of the emulsion on pigments and fillers by adding monoethylenically unsaturated monocarboxylic acids in the later stage of polymerization, so that the monoethylenically unsaturated monocarboxylic acids are appropriately enriched in the surface layer, and can effectively prevent the rain mark problem caused by the migration of the wetting and dispersing agent in the coating film. DETAILED DESCRIPTION

[0047] In order to better understand the technical solution of the present invention, the content of the present invention is further described below in conjunction with the embodiments, but the content of the present invention is not limited to the following embodiments.

[0048] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0049] The present invention will be further described below in conjunction with specific examples. It should be understood that the following examples are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0050] The "%" involved in the following examples, unless otherwise specified, refers to the mass percentage.

[0051] Polymerizable benzophenone is a product of Aladdin Company, and its structural formula is as follows:

[0052] Wherein, R is a methyl group.

[0053] Benzophenone (common small molecule photoinitiator) is a product of Aladdin Company, and its structural formula is as follows:

[0054]

[0055] Allyloxy fatty alcohol oxyethylene ether ammonium sulfate SR-10 (EO number is 10) is a product of Aidico Company;

[0056] Allyloxy fatty alcohol oxyethylene ether ammonium sulfate SR-20 (EO number is 20) is a product of Aidico Company;

[0057] Multifunctional anionic monomer: Sodium vinylbenzenesulfonate is a product of Shandong Xingzhilian Company;

[0058] Buffer: Sodium bicarbonate is a product of Sinopharm Reagent Company;

[0059] The hydrolyzable Si organic bond monomer: γ-glycidyloxypropyltrimethoxysilane (i.e. A-187) is a product of Momentive Corporation;

[0060] Inhibitor TEMPO: product of Aladdin;

[0061] Defoamer B-943 is a product of ADEKA.

[0062] Fungicide LX-150, KORDEK: products of Dow Chemical Company.

[0063] Example 1

[0064] The raw materials were weighed according to the following mass: methyl methacrylate 7g (a), styrene 8g (a), n-butyl acrylate 15g (b), isooctyl acrylate 5g (b), sodium vinylbenzenesulfonate 0.1g (multifunctional anionic monomer), polymerizable benzophenone 0.5g (d), itaconic acid 0.2g (c), acrylic acid 0.3g (c), A-187 1.0g (e), SR-10 0.56g (emulsifier), sodium bicarbonate 0.4g (buffer), ammonium persulfate 0.2g (oxidant), sodium metabisulfite 0.3g (reducing agent), tert-butyl hydroperoxide 0.1g (post-treatment agent), isoascorbic acid 0.05g (post-treatment agent) and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0065] 1) Preparing a pre-emulsion: at room temperature and pressure, add 0.5 g SR-10, 0.1 g sodium vinylbenzene sulfonate, 0.2 g itaconic acid and 35 g deionized water to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and then add 7 g methyl methacrylate, 8 g styrene, 15 g n-butyl acrylate, 5 g isooctyl acrylate, 0.225 g acrylic acid and 0.5 g polymerizable benzophenone, stir and mix thoroughly for use;

[0066] 2) Preparation of bottom liquid: Add 0.06 g SR-10, 0.001 g TEMPO and 40 g deionized water to a reaction kettle equipped with a stirrer, a condenser and a constant flow pump at room temperature and pressure, and heat to 70°C;

[0067] 3) Prepare oxidant solution: add 0.2g ammonium persulfate, 0.4g sodium bicarbonate and 3.5g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0068] 4) Prepare a reducing agent solution: add 0.3 g of sodium pyrosulfite and 5.25 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0069] 5) When the temperature in the reactor reaches 70° C., add 10% of the pre-emulsion, 10% of the oxidant solution and 10% of the reductant solution in the reactor in sequence, react for 10 minutes under stirring, and then drop the remaining pre-emulsion, oxidant solution and reductant solution into the reactor through a constant flow pump feeding device. When 17% of the pre-emulsion remains, stop dropping; add the remaining 0.075 g of acrylic acid at one time, mix well, and continue to drop the remaining pre-emulsion, oxidant and reductant solutions, ensuring that the dropping time of the oxidant solution and the reductant solution is longer than that of the pre-emulsion. After the dropping is completed, keep warm for 30 minutes;

[0070] 6) adding a post-treatment agent, namely, an aqueous solution of 0.1 g of tert-butyl hydroperoxide and an aqueous solution of 0.05 g of isoascorbic acid, to the reaction kettle, cooling the mixture to 20° C., then adding 1.0 g of A-187, 0.03 g of a defoamer, and 0.4 g of a fungicide, adjusting the pH to 9.0 with aqueous ammonia, and filtering the mixture to obtain the acrylic elastic emulsion.

[0071] Example 2

[0072] The raw materials were weighed according to the following mass: methyl methacrylate 10g (a), styrene 10g (a), n-butyl acrylate 20g (b), isooctyl acrylate 20g (b), sodium vinylbenzenesulfonate 0.5g (multifunctional anionic monomer), polymerizable benzophenone 1.5g (d), itaconic acid 1.5g (c), acrylic acid 1.0g (c), A-187 1.5g (e), SR-10 2.5g (emulsifier), sodium bicarbonate 0.7g (buffer), ammonium persulfate 0.5g (oxidant), sodium metabisulfite 0.75g (reducing agent), tert-butyl hydroperoxide 0.5g (post-treatment agent), isoascorbic acid 0.25g (post-treatment agent) and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0073] 1) Preparing a pre-emulsified liquid: at room temperature and pressure, add 2.0 g SR-10, 0.5 g sodium vinylbenzene sulfonate, 1.5 g itaconic acid and 35 g deionized water to a pre-emulsified tank equipped with a monomer metering tank and a stirrer, and then add 10 g methyl methacrylate, 10 g styrene, 20 g n-butyl acrylate, 20 g isooctyl acrylate, 0.65 g acrylic acid and 1.5 g polymerizable benzophenone, stir and mix thoroughly for use;

[0074] 2) Preparation of bottom liquid: at room temperature and pressure, add 0.005 g TEMPO, 0.5 g SR-10, and 50 g deionized water to a reaction kettle equipped with a stirrer, a condenser, and a constant flow pump feeding device, and heat to 55°C;

[0075] 3) Prepare oxidant solution: add 0.5g ammonium persulfate, 0.7g sodium bicarbonate and 7.5g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, and stir until completely dissolved for later use;

[0076] 4) Prepare a reducing agent solution: add 0.75 g of sodium pyrosulfite and 11.25 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0077] 5) When the temperature in the reactor reaches 55° C., add 1% of the pre-emulsion, 40% of the oxidant solution by weight and 40% of the reducing agent solution by weight to the reactor in sequence, react for 20 minutes under stirring, and then drop the remaining pre-emulsion, oxidant solution and reducing agent solution to the reactor through a constant flow pump feeding device. When 10% of the pre-emulsion remains, stop dropping, add 0.35 g of acrylic acid at one time, mix well, and continue to drop the remaining pre-emulsion, oxidant and reducing agent solutions, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion. After the dropping is completed, keep warm for 45 minutes;

[0078] 6) adding a post-treatment agent, namely, an aqueous solution of 0.5 g of tert-butyl hydroperoxide and an aqueous solution of 0.25 g of isoascorbic acid to the reaction kettle, cooling the reaction kettle to 45° C., adding 1.5 g of A-187, 0.041 g of a defoamer, and 0.5 g of a fungicide, adjusting the pH to 7.0 with aqueous ammonia, and filtering the reaction kettle to obtain the acrylic elastic emulsion.

[0079] Example 3

[0080] The raw materials were weighed according to the following mass: methyl methacrylate 15g (a), styrene 20g (a), n-butyl acrylate 20g (b), isooctyl acrylate 25g (b), sodium vinylbenzenesulfonate 1.0g (multifunctional anionic monomer), polymerizable benzophenone 5.0g (d), itaconic acid 3.0g (c), acrylic acid 2.0g (c), A-187 5.0g (e), SR-20 3.5g (emulsifier), sodium bicarbonate 1.0g (buffer), ammonium persulfate 1.0g (oxidant), sodium metabisulfite 1.5g (reducing agent), tert-butyl hydroperoxide 1.0g (post-treatment agent), isoascorbic acid 0.5g (post-treatment agent) and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0081] 1) Preparing a pre-emulsion: at room temperature and pressure, add 3.0 g SR-20, 1.0 g sodium vinylbenzene sulfonate, 3.0 g itaconic acid and 55 g deionized water to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and then add 15 g methyl methacrylate, 20 g styrene, 20 g n-butyl acrylate, 25 g isooctyl acrylate, 1.0 g acrylic acid and 5.0 g polymerizable benzophenone, mix well and set aside;

[0082] 2) Preparation of bottom liquid: Add 0.01 g TEMPO, 0.5 g SR-20 and 50 g deionized water to a reaction kettle equipped with a stirrer, a condenser and a constant flow pump at room temperature and pressure, and heat to 75°C;

[0083] 3) Prepare oxidant solution: add 1.0g ammonium persulfate, 1.0g sodium bicarbonate and 20g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0084] 4) Prepare a reducing agent solution: add 1.5 g of sodium pyrosulfite and 30 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, and stir until completely dissolved for later use;

[0085] 5) When the temperature in the reactor reaches 75°C, add 2% of the pre-emulsion, 30% by weight of the oxidant solution and 30% by weight of the reducing agent solution to the reactor in sequence, react for 15 minutes under stirring, and then drop the remaining pre-emulsion, oxidant solution and reducing agent solution to the reactor through a constant flow pump feeding device. When 25% of the pre-emulsion remains, stop dropping; add 1.0g of acrylic acid at one time, mix well, and continue to drop the remaining pre-emulsion, oxidant and reducing agent solutions, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion. After the dropping is completed, keep warm for 30 minutes;

[0086] 6) adding a post-treatment agent, namely, an aqueous solution of 1.0 g of tert-butyl hydroperoxide and an aqueous solution of 0.5 g of isoascorbic acid to the reaction kettle, cooling the reaction kettle to 20° C., adding 5.0 g of A-187, 0.06 g of a defoamer, and 0.78 g of a fungicide, adjusting the pH to 8.0 with aqueous ammonia, and filtering the reaction kettle to obtain the acrylic elastic emulsion.

[0087] Example 4

[0088] The raw materials were weighed according to the following mass: methyl methacrylate 10g (a), styrene 5g (a), n-butyl acrylate 15g (b), isooctyl acrylate 20g (b), sodium vinylbenzenesulfonate 0.4g (multifunctional anionic monomer), polymerizable benzophenone 1.0g (d), itaconic acid 2.0g (c), acrylic acid 1.5g (c), A-187 2.5g (e), SR-10 1.0g (emulsifier), sodium bicarbonate 0.55g (buffer), ammonium persulfate 0.5g (oxidant), sodium metabisulfite 0.75g (reducing agent), tert-butyl hydroperoxide 0.3g (post-treatment agent), isoascorbic acid 0.15g (post-treatment agent), and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0089] 1) Preparing a pre-emulsion: at room temperature and pressure, add 0.75 g SR-10, 0.4 g sodium vinylbenzene sulfonate, 2.0 g itaconic acid, 40 g deionized water, 10 g methyl methacrylate, 5 g styrene, 15 g n-butyl acrylate, 20 g isooctyl acrylate, 1.05 g acrylic acid, 1.0 g polymerizable benzophenone to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and stir and mix thoroughly for use;

[0090] 2) Preparation of bottom liquid: Add 0.006 g TEMPO, 0.25 g SR-10 and 45 g deionized water to a reaction kettle equipped with a stirrer, a condenser and a constant flow pump at room temperature and pressure, and heat to 60°C;

[0091] 3) Prepare oxidant solution: add 0.5g ammonium persulfate, 0.55g sodium bicarbonate and 7g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0092] 4) Prepare a reducing agent solution: add 0.75 g of sodium pyrosulfite and 10.5 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0093] 5) When the temperature in the reactor reaches 60° C., add 5% of the total amount of the pre-emulsion, 60% of the oxidant solution by mass and 60% of the reducing agent solution by mass to the reactor in sequence, react for 20 minutes under stirring, and then drop the remaining pre-emulsion, oxidant solution and reducing agent solution to the reactor through a constant flow pump feeding device. When 15% of the pre-emulsion remains, stop dropping; add 0.45 g of acrylic acid at one time, mix well, and continue to drop the remaining pre-emulsion, oxidant and reducing agent solutions, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion, and keep warm for 90 minutes after the dropping is completed;

[0094] 6) adding a post-treatment agent, namely, an aqueous solution of 0.3 g of tert-butyl hydroperoxide and an aqueous solution of 0.15 g of isoascorbic acid to the reaction kettle, cooling the reaction kettle to 30° C., adding 2.5 g of A-187, 0.038 g of a defoamer, and 0.46 g of a fungicide, adjusting the pH to 8.5 with aqueous ammonia, and filtering the reaction kettle to obtain the acrylic elastic emulsion.

[0095] Example 5

[0096] The raw materials were weighed according to the following mass: methyl methacrylate 20g (a), styrene 10g (a), n-butyl acrylate 10g (b), isooctyl acrylate 30g (b), sodium vinylbenzenesulfonate 0.8g (multifunctional anionic monomer), polymerizable benzophenone 2.0g (d), itaconic acid 1.2g (c), acrylic acid 0.8g (c), A-187 3.5g (e), SR-10 3.0g (emulsifier), sodium bicarbonate 0.85g (buffer), ammonium persulfate 0.8g (oxidant), sodium metabisulfite 1.2g (reducing agent), tert-butyl hydroperoxide 0.7g (post-treatment agent), isoascorbic acid 0.35g (post-treatment agent), and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0097] 1) Preparing a pre-emulsion: at room temperature and pressure, add 2.0 g SR-10, 0.8 g sodium vinylbenzene sulfonate, 1.2 g itaconic acid and 50 g deionized water to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and then add 20 g methyl methacrylate, 10 g styrene, 10 g n-butyl acrylate, 30 g isooctyl acrylate, 0.48 g acrylic acid and 2.0 g polymerizable benzophenone, stir and mix thoroughly for use;

[0098] 2) Preparation of bottom liquid: at room temperature and pressure, add 0.008 g TEMPO, 1.0 g SR-10, and 55 g deionized water into a reaction kettle equipped with a stirrer, a condenser, and a constant flow pump feeding device, and heat to 65°C;

[0099] 3) Prepare oxidant solution: add 0.8g ammonium persulfate, 0.85g sodium bicarbonate and 12g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0100] 4) Prepare a reducing agent solution: add 1.2 g of sodium pyrosulfite and 18 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0101] 5) When the temperature in the reactor reaches 65° C., add 8% of the total amount of the pre-emulsion, 50% by weight of the oxidant solution and 50% by weight of the reducing agent solution to the reactor in sequence, react for 20 minutes under stirring, and then drop the remaining pre-emulsion, oxidant solution and reducing agent solution to the reactor through a constant flow pump feeding device. When 20% of the pre-emulsion remains, stop dropping; add 0.32 g of acrylic acid at one time, mix well, and continue to drop the remaining pre-emulsion, oxidant and reducing agent solutions, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion, and keep warm for 60 minutes after the dropping is completed;

[0102] 6) adding a post-treatment agent, namely, an aqueous solution of 0.7 g of tert-butyl hydroperoxide and an aqueous solution of 0.35 g of isoascorbic acid to the reaction kettle, cooling the reaction kettle to 45° C., adding 3.5 g of A-187, 0.051 g of a defoamer, and 0.61 g of a fungicide, adjusting the pH to 7.5 with aqueous ammonia, and filtering the reaction kettle to obtain the acrylic elastic emulsion.

[0103] Comparative Example 1

[0104] The difference between this comparative example and Example 3 is that 5.0 g of small molecule benzophenone is used to replace 5.0 g of polymerizable benzophenone, and the other components and the emulsion preparation method are exactly the same as those in Example 3.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 3 is that no polymerizable benzophenone is added to the raw material components, and the other components and the emulsion preparation method are exactly the same as those in Example 3.

[0107] Comparative Example 3

[0108] The raw materials were weighed according to the following mass: methyl methacrylate 20g (a), styrene 10g (a), n-butyl acrylate 10g (b), isooctyl acrylate 30g (b), sodium vinylbenzenesulfonate 0.8g (multifunctional anionic monomer), polymerizable benzophenone 2.0g (d), acrylic acid 2g (c), A-1873.5g (e), SR-10 3.0g (emulsifier), sodium bicarbonate 0.85g (buffer), ammonium persulfate 0.8g (oxidant), sodium metabisulfite 1.2g (reducing agent), tert-butyl hydroperoxide 0.7g (post-treatment agent), isoascorbic acid 0.35g (post-treatment agent), and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0109] 1) Preparing a pre-emulsion: at room temperature and pressure, add 2.0 g SR-10, 0.8 g sodium vinylbenzene sulfonate and 50 g deionized water to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and then add 20 g methyl methacrylate, 10 g styrene, 10 g n-butyl acrylate, 30 g isooctyl acrylate, 1.2 g acrylic acid and 2.0 g polymerizable benzophenone, stir and mix thoroughly for use;

[0110] 2) Preparation of bottom liquid: at room temperature and pressure, add 0.008 g TEMPO, 1.0 g SR-10, and 55 g deionized water into a reaction kettle equipped with a stirrer, a condenser, and a constant flow pump feeding device, and heat to 65°C;

[0111] 3) Prepare oxidant solution: add 0.8g ammonium persulfate, 0.85g sodium bicarbonate and 12g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0112] 4) Prepare a reducing agent solution: add 1.2 g of sodium pyrosulfite and 18 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0113] 5) When the temperature in the reactor reaches 65° C., add 8% of the total amount of the pre-emulsion, 50% by weight of the oxidant solution and 50% by weight of the reducing agent solution to the reactor in sequence, react for 20 minutes under stirring, and then drop the remaining pre-emulsion, oxidant solution and reducing agent solution to the reactor through a constant flow pump feeding device. When 20% of the pre-emulsion remains, stop dropping; add 0.8 g of acrylic acid at one time, mix well, and continue to drop the remaining pre-emulsion, oxidant and reducing agent solutions, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion, and keep warm for 60 minutes after the dropping is completed;

[0114] 6) adding a post-treatment agent, namely, an aqueous solution of 0.7 g of tert-butyl hydroperoxide and an aqueous solution of 0.35 g of isoascorbic acid to the reaction kettle, cooling the reaction kettle to 45° C., adding 3.5 g of A-187, 0.051 g of a defoamer, and 0.61 g of a fungicide, adjusting the pH to 7.5 with aqueous ammonia, and filtering the reaction kettle to obtain the acrylic elastic emulsion.

[0115] Comparative Example 4

[0116] The raw materials were weighed according to the following mass: methyl methacrylate 15g (a), styrene 20g (a), n-butyl acrylate 20g (b), isooctyl acrylate 25g (b), sodium vinylbenzenesulfonate 1.0g (multifunctional anionic monomer), polymerizable benzophenone 5.0g (d), acrylic acid 5.0g (c), A-1875.0g (e), SR-20 3.5g (emulsifier), sodium bicarbonate 1.0g (buffer), ammonium persulfate 1.0g (oxidant), sodium metabisulfite 1.5g (reducing agent), tert-butyl hydroperoxide 1.0g (post-treatment agent), isoascorbic acid 0.5g (post-treatment agent) and appropriate amounts of ammonia water (pH adjuster) and deionized water.

[0117] 1) Preparing a pre-emulsion: at room temperature and pressure, add 3.0 g SR-20, 1.0 g sodium vinylbenzene sulfonate and 55 g deionized water to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and then add 15 g methyl methacrylate, 20 g styrene, 20 g n-butyl acrylate, 25 g isooctyl acrylate, 5.0 g acrylic acid and 5.0 g polymerizable benzophenone, mix well and set aside;

[0118] 2) Preparation of bottom liquid: Add 0.01 g TEMPO, 0.5 g SR-20 and 50 g deionized water to a reaction kettle equipped with a stirrer, a condenser and a constant flow pump at room temperature and pressure, and heat to 75°C;

[0119] 3) Prepare oxidant solution: add 1.0g ammonium persulfate, 1.0g sodium bicarbonate and 20g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0120] 4) Prepare a reducing agent solution: add 1.5 g of sodium pyrosulfite and 30 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, and stir until completely dissolved for later use;

[0121] 5) When the temperature in the reactor reaches 75° C., add 2% of the pre-emulsion, 30% by weight of the oxidant solution and 30% by weight of the reducing agent solution into the reactor in sequence, react for 15 minutes under stirring, and then dropwise add the remaining pre-emulsion, oxidant solution and reducing agent solution into the reactor through a constant flow pump feeding device, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion, and keep warm for 30 minutes after the dropping is completed;

[0122] 6) adding a post-treatment agent, namely, an aqueous solution of 1.0 g of tert-butyl hydroperoxide and an aqueous solution of 0.5 g of isoascorbic acid to the reaction kettle, cooling the reaction kettle to 20° C., adding 5.0 g of A-187, 0.06 g of a defoamer, and 0.78 g of a fungicide, adjusting the pH to 8.0 with aqueous ammonia, and filtering the reaction kettle to obtain the acrylic elastic emulsion.

[0123] Comparative Example 5

[0124] The raw materials were weighed according to the following mass: 15 g (a) of methyl methacrylate, 20 g (a) of styrene, 20 g (b) of n-butyl acrylate, 25 g (b) of isooctyl acrylate, 1.0 g (a) of sodium vinylbenzenesulfonate (multifunctional anionic monomer), 5.0 g (c) of acrylic acid, 3.5 g (emulsifier) ​​of sodium dodecyl sulfate, 1.0 g (buffer) of sodium bicarbonate, 1.0 g (oxidant) of ammonium persulfate, 1.5 g (reducing agent) of sodium metabisulfite, 1.0 g (post-treatment agent) of tert-butyl hydroperoxide, 0.5 g (post-treatment agent) of isoascorbic acid, and appropriate amounts of aqueous ammonia (pH adjuster) and deionized water.

[0125] 1) Preparing a pre-emulsion: at room temperature and pressure, add 2.0 g of sodium dodecyl sulfate, 1.0 g of sodium vinylbenzene sulfonate, and 55 g of deionized water to a pre-emulsification tank equipped with a stirrer and a monomer metering tank, and then add 15 g of methyl methacrylate, 20 g of styrene, 20 g of n-butyl acrylate, 25 g of isooctyl acrylate, and 5.0 g of acrylic acid, stir and mix thoroughly, and set aside;

[0126] 2) Preparation of bottom liquid: Add 0.01 g TEMPO, 0.5 g sodium dodecyl sulfate and 50 g deionized water to a reaction kettle equipped with a stirrer, a condenser and a constant flow pump at room temperature and pressure, and heat to 75°C;

[0127] 3) Prepare oxidant solution: add 1.0g ammonium persulfate, 1.0g sodium bicarbonate and 20g deionized water into an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0128] 4) Prepare a reducing agent solution: add 1.5 g of sodium pyrosulfite and 30 g of deionized water to an initiator tank equipped with a stirrer and a constant current dripping device at room temperature and pressure, mix well and set aside;

[0129] 5) When the temperature in the reactor reaches 75° C., add 2% of the pre-emulsion, 30% by weight of the oxidant solution and 30% by weight of the reducing agent solution into the reactor in sequence, react for 15 minutes under stirring, and then dropwise add the remaining pre-emulsion, oxidant solution and reducing agent solution into the reactor through a constant flow pump feeding device, ensuring that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion, and keep warm for 60 minutes after the dropping is completed;

[0130] 6) adding a post-treatment agent, namely, an aqueous solution of 1.0 g of tert-butyl hydroperoxide and an aqueous solution of 0.5 g of isoascorbic acid, to the reaction kettle, cooling the mixture to 20° C., adding 0.03 g of a defoamer and 0.4 g of a fungicide, adjusting the pH to 9.0 with aqueous ammonia, and filtering the mixture to obtain the acrylic elastic emulsion.

[0131] Application example: latex paint preparation and performance analysis

[0132] The emulsions obtained in Examples 1-5 and Comparative Examples 1-4 were used for building exterior wall elastic coatings, and latex paints were prepared according to the following formula:

[0133] Table 1: Coating test formulations

[0134] Raw material name Addition amount (g) Remark water 200 250HBR 3.5 Cellulose GA40 7.5 Dispersants BD-109 2.0 Wetting Agents SN-154 2.5 Defoaming agent PG 10 antifreeze AMP-95 1.0 pH Adjuster R996 160 Titanium dioxide Calcined clay 25 Calcined Kaolin Barium sulfate 50 filler 1500 mesh heavy calcium 110 Heavy Calcium Lotion 350 Lotion Texanol 5.0 Film-forming aids Youchuang E 50 A10 2.5 Defoaming agent U505 1.2 Thickener preservative 2.5 preservative Antifungal agent 2.0 Antifungal agent water 15.3 total 1000

[0135] The testing method is carried out according to the following standards:

[0136] Rain mark resistance: Take A4 size tinplate, according to 120g / m 2 Apply by brush, and after curing for 3 hours under standard environment, apply 120g / m 2 Apply the coating amount by brushing, and maintain for 3 hours under standard environment; bend the tinplate coated with latex paint at a position 10cm away from one end, bend the tinplate into 90°, and fix it to the edge of the table with paper tape to ensure that a part of the lower end of the tinplate protrudes out of the table; use a spray pot filled with pure water to spray an appropriate amount of water on the upper end of the tinplate coating to ensure that there is water flow left, and the water flow will not drip when it flows to the lower end of the tinplate coating, and it can be retained for a long time; leave it for one night and observe the appearance of the coating (water marks on the vertical surface and the bottom);

[0137] Stain resistance: According to GB / T 9755-2014 exterior wall standard, the oven rapid method is cycled twice (the lower the reflection coefficient decrease rate, the better the stain resistance);

[0138] Mechanical properties: in accordance with the requirements of JG / T 172-2014 "Elastic Architectural Coatings".

[0139] The test results are shown in Table 2.

[0140] Table 2: Coating test results

[0141]

[0142] As shown in Table 2, the exterior wall elastic coating prepared by using the emulsion of the present invention has excellent mechanical properties, stain resistance and rain mark resistance.

Claims

1. An acrylic emulsion for building exterior wall coating, characterized in that: The acrylic emulsion is prepared by comprising the following components in parts by weight as raw materials: a) 15 to 35 parts by mass of a monovinyl aromatic monomer; b) 20 to 45 parts by mass of alkyl (meth)acrylate; c) 0.5 to 5 parts by mass of C containing α,β-monoethylenically unsaturated bonds 3-6 Monocarboxylic acid and C 3-6 dicarboxylic acids; d) 0.5 to 5.0 parts by weight of a polymerizable benzophenone photoinitiator; e) 1.0 to 5.0 parts by mass of a monomer having a hydrolyzable Si-organic bond; Wherein, in component d), the polymerizable benzophenone photoinitiator has a structure as shown in the following formula: Wherein, x is from 2 to 13, y is from 5 to 20, and x+y≤25; R is selected from the group consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, tert-butyl, pentyl, isopentyl, and sec-pentyl.

2. The acrylic emulsion according to claim 1, characterized in that Component a) is 15 to 30 parts by mass of a monovinyl aromatic monomer.

3. The acrylic emulsion according to claim 1, characterized in that Component b) is 25 to 40 parts by mass of an alkyl (meth)acrylate.

4. The acrylic emulsion according to claim 1, characterized in that Component c) is 2.0 to 5.0 parts by weight of C containing α,β-monoethylenically unsaturated bonds. 3-6 Monocarboxylic acid and C 3-6 Dicarboxylic acid.

5. The acrylic emulsion according to claim 1, characterized in that Component d) is 0.5 to 2.0 parts by weight of a polymerizable benzophenone photoinitiator.

6. The acrylic emulsion according to claim 1, characterized in that Component e) is 1.5 to 3.5 parts by mass of a monomer having a hydrolyzable Si-organic bond.

7. The acrylic emulsion according to claim 1, characterized in that In component c), the C 3-6 The monocarboxylic acid is selected from one or more of acrylic acid, methacrylic acid, ethacrylic acid, allyl acetic acid, crotonic acid or vinyl acetic acid; The C 3-6 The dicarboxylic acid is selected from one or more of itaconic acid, fumaric acid, maleic acid or 2-methylmaleic acid.

8. The acrylic emulsion according to claim 7, characterized in that In component c), the C 3-6 The monocarboxylic acid is selected from acrylic acid and methacrylic acid.

9. The acrylic emulsion according to claim 7, characterized in that: In component c), the C 3-6 The dicarboxylic acid is selected from itaconic acid.

10. The acrylic emulsion according to claim 1, characterized in that: In component d), in the structure of the polymerizable benzophenone photoinitiator, x is 8-10, and y is 6-18.

11. The acrylic emulsion according to claim 1, characterized in that: In the structure of the polymerizable benzophenone photoinitiator, R is selected from methyl or ethyl.

12. The acrylic emulsion according to any one of claims 1 to 11, characterized in that The monovinyl aromatic monomer in component a) is selected from styrene, 2-methylstyrene, 4-methylstyrene, 2-(n-butyl)styrene, 4-(n-butyl)styrene and / or 4-(n-decyl)styrene.

13. The acrylic emulsion according to claim 12, characterized in that: The monovinyl aromatic monomer in component a) is selected from styrene.

14. The acrylic emulsion according to claim 12, characterized in that: The alkyl (meth)acrylate in component b) is selected from one or more of n-butyl acrylate, isobutyl acrylate, sec-butyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, sec-butyl methacrylate, n-hexyl methacrylate and 2-ethylhexyl methacrylate; The monomer having a hydrolyzable Si-organic bond in the component e) is selected from one or more of γ-glycidyloxypropyltrimethoxysilane, γ-glycidyloxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane or β-(3,4-epoxycyclohexyl)-ethyltriethoxysilane.

15. The acrylic emulsion according to claim 14, characterized in that The component b) is an alkyl (meth)acrylate selected from methyl methacrylate, n-butyl acrylate and 2-ethylhexyl acrylate.

16. The acrylic emulsion according to claim 14, characterized in that The monomer having a hydrolyzable Si-organic bond in the component e) is selected from β-(3,4-epoxycyclohexyl)-ethyltrimethoxysilane and γ-glycidyloxypropyltrimethoxysilane.

17. The acrylic emulsion according to claim 16, characterized in that The monomer having a hydrolyzable Si-organic bond is selected from γ-glycidyloxypropyltrimethoxysilane.

18. A method for preparing the acrylic emulsion according to any one of claims 1 to 17, characterized in that: The steps include: 1) preparing a pre-emulsion: taking a portion of an emulsifier, 0.1-1.0 parts by weight of a multifunctional anionic monomer and 25-55 parts by weight of deionized water, adding the component a), component b), component d) and a portion of component c) thereto, mixing and setting aside; 2) preparing the bottom liquid: adding the remaining emulsifier, 0.001-0.01 parts by weight of polymerization inhibitor and 30-60 parts by weight of deionized water into the reaction kettle, heating to 50-75° C. for standby use; 3) preparing an oxidant solution: mixing 0.2-1.0 parts by weight of an oxidant, 0.1-1.0 parts by weight of a buffer and 3.5-10 parts by weight of deionized water for later use; 4) preparing a reducing agent solution: mixing 0.3-1.5 parts by weight of a reducing agent and 5-15 parts by weight of deionized water for later use; 5) at 50-75° C., add 1%-10% by weight of a pre-emulsion, 10%-60% by weight of an oxidant solution and 10%-60% by weight of a reducing agent solution to the bottom liquid of the kettle in sequence, react for 10-30 minutes, and then dropwise add the remaining pre-emulsion, oxidant solution and reducing agent solution thereto; when 10%-25% of the pre-emulsion remains, stop dropping, add the remaining component c) thereto at one time, mix well, and continue to dropwise add the remaining pre-emulsion, oxidant solution and reducing agent solution, and ensure that the dropping time of the oxidant solution and the reducing agent solution is longer than the dropping time of the pre-emulsion; After the addition is completed, keep warm for 30-90 minutes; 6) After adding the post-treatment agent dropwise into the reaction kettle, the temperature is lowered to 15-45° C., and then component e), a defoamer, and a bactericide are added thereto, and the pH is adjusted to 7.0-9.0, and the acrylic emulsion is obtained after filtering.

19. The method according to claim 18, characterized in that Based on the mass of the emulsifier being 100%, the emulsifier added in step 1) is 65-90%, and the emulsifier is selected from fatty alcohol oxyethylene ether ammonium sulfate; The multifunctional anionic monomer is selected from one or more of sodium vinyl sulfonate, sodium vinylbenzene sulfonate, sodium 3-allyloxy-1-hydroxy-propane sulfonate or sodium 2-acrylamide-2-methylpropane sulfonate; In step 1), the added component c) comprises the C 3-6 dicarboxylic acid and a portion of the C 3-6 Monocarboxylic acid.

20. The method according to claim 19, characterized in that In step 1), the emulsifier is selected from allyloxy fatty alcohol oxyethylene ether ammonium sulfate, and the number of ethylene oxide is 3-30.

21. The method according to claim 19, characterized in that The multifunctional anionic monomer is selected from sodium vinylbenzene sulfonate.

22. The method according to claim 19, characterized in that In step 1), the C 3-6 The mass of the monocarboxylic acid is 100%, and the C 3-6 The monocarboxylic acid is 50-80%.

23. The method according to claim 18, characterized in that The buffer in step 3) is selected from one or more of sodium carbonate, sodium bicarbonate, sodium phosphate or sodium dihydrogen phosphate; The oxidant is selected from water-soluble oxidants; In step 4), the reducing agent is selected from one or more of sodium sulfite, sodium bisulfite or sodium pyrosulfite.

24. The method according to claim 23, characterized in that In step 3), the buffer is selected from sodium bicarbonate.

25. The method according to claim 23, characterized in that In step 3), the oxidant is selected from ammonium persulfate.

26. The method according to claim 23, characterized in that In step 4), the reducing agent is selected from sodium pyrosulfite.

27. The method according to any one of claims 18 to 26, characterized in that In step 5), the total time of adding the pre-emulsion is controlled within 180-300 min; In step 6), the time for adding the post-treatment agent is 30-60 minutes, and the temperature is kept warm for 30-60 minutes after the addition is completed; wherein the post-treatment agent is selected from one or more of tert-butyl hydroperoxide, tert-amyl hydroperoxide, sodium bisulfite, sodium dithionite and isoascorbic acid.

28. The method according to claim 27, characterized in that In step 5), the dripping time of the oxidant solution and the reducing agent solution is 5-20 min longer than the dripping time of the pre-emulsion.

29. The method according to claim 27, characterized in that The post-treatment agent is selected from tert-butyl hydroperoxide and / or isoascorbic acid.

30. The method according to claim 27, characterized in that The post-treatment agent is a mixture of tert-butyl hydroperoxide and isoascorbic acid in a mass ratio of 2:

1.

31. A latex paint, characterized in that: The latex paint comprises the acrylic emulsion according to any one of claims 1 to 17 or the acrylic emulsion prepared by the method according to any one of claims 18 to 30.

32. The latex paint according to claim 31, characterized in that The latex paint is applied to exterior wall elastic latex paint.

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