Acrylic emulsion for inorganic silicate coating as well as preparation method and application of acrylic emulsion

Abstract

The invention discloses an acrylic emulsion for an inorganic silicate coating as well as a preparation method and application of the acrylic emulsion, and belongs to the technical field of waterborne acrylic emulsions. The preparation raw materials of the acrylic emulsion for the inorganic silicate coating comprise the following components: unsaturated carboxylic acid, a functional monomer, a soft monomer, a hard monomer, a polymerizable emulsifier, an initiator, a functional additive and water. According to the acrylic emulsion, a polymerizable emulsifier is adopted, an emulsifier structural unit is bonded with an acrylic polymer through a covalent bond, the stability of the acrylic emulsion is improved, a functional monomer with a post-crosslinking effect is added, a micro-crosslinking structure is formed in emulsion particles, and the possibility of agglomeration of the emulsion particles is reduced. The inorganic silicate coating is good in thermal stability and can still effectively form a film after being subjected to high-temperature thermal storage for 2 months, the properties of a paint film of the coating can still meet various index requirements, and actual construction requirements are met.

Description

Technical Field

[0001] The invention belongs to the technical field of water-based acrylic emulsions, and in particular relates to an acrylic emulsion for inorganic silicate coatings, a preparation method and an application thereof. Background Art

[0002] Inorganic silicate coatings mainly use potassium silicate and silica sol as film-forming substances, and have the advantages of high hardness, high temperature resistance, and aging resistance. Since inorganic silicate coatings have high cross-linking density and large internal stress, and are prone to powdering and cracking, in practical applications, they often need to be combined with a small amount of polymer emulsion to improve the flexibility and film-forming properties of the coating. However, silicate solutions are highly alkaline and have high salt concentrations. Ordinary polymer emulsions mostly use small molecule external emulsifiers, such as sodium dodecylbenzene sulfonate, sodium dodecyl sulfate, alkylphenol polyoxyethylene ether, etc., and the emulsion stability is poor. It is very easy to demulsify and settle in potassium silicate solution, which affects the storage stability and ease of construction of the coating, and cannot meet the performance requirements of inorganic silicate coatings during use.

[0003] Patent CN 112251056 B discloses a styrene acrylic emulsion prepared with acrylamide as a cross-linking monomer, disodium alkyl polyoxyethylene ether succinate monoester sulfonate (A-102) and alkyl polyoxyethylene ether (LCN-118). After the styrene acrylic emulsion is compounded with potassium silicate, the system shows good compatibility. However, polyacrylamide hydrolyzes to generate ammonia in the strong alkaline environment of silicate (pH>12), resulting in an increase in the VOC content of the coating and poor environmental protection. Summary of the invention

[0004] In order to solve the disadvantage of poor stability of polymer emulsion in inorganic silicate coating, the present invention provides an acrylic emulsion for inorganic silicate coating, a preparation method and application. The acrylic emulsion of the present invention adopts a polymerizable emulsifier, and the emulsifier structural unit is bonded to the acrylic polymer through a covalent bond, thereby improving the stability of the acrylic emulsion, and adding a functional monomer that plays a post-crosslinking role to form a micro-crosslinking structure inside the emulsion particles, thereby reducing the possibility of emulsion particle agglomeration.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] An acrylic emulsion for inorganic silicate coating, the raw materials for its preparation include the following components in parts by mass:

[0007]

[0008]

[0009] Wherein, the functional monomer is an unsaturated glycidyl ether or an unsaturated glycidyl ester;

[0010] The polymerizable emulsifier is one or a combination of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate (DNS-86), allyloxy isotridecyl alcohol polyoxyethylene ether sulfate ammonium salt (MAX-100) or sodium acrylamido isopropyl sulfonate.

[0011] Furthermore, the raw materials for preparing the acrylic emulsion for inorganic silicate coating also include a polymer protective glue, which can increase the stability of emulsion polymerization, reduce the coagulation rate and maintain a low viscosity of the emulsion; the polymer protective glue can be polyacrylic acid partial sodium salt, and the amount of the polymer protective glue is 0.5% to 1.5% of the total material mass.

[0012] Furthermore, the unsaturated carboxylic acid is selected from one or a combination of acrylic acid and methacrylic acid;

[0013] Furthermore, the soft monomer is an acrylic soft monomer, selected from one or more combinations of ethyl acrylate, butyl acrylate, octyl acrylate, and octyl methacrylate;

[0014] Further, the hard monomer is selected from one or a combination of styrene and methyl methacrylate;

[0015] Furthermore, the initiator is a persulfate thermal initiator, such as ammonium persulfate, potassium persulfate, sodium persulfate, etc.

[0016] Furthermore, the functional additive is one or more combinations of defoamers and bactericides; the defoamer is a mineral oil defoamer or a silicone defoamer, and the amount of the defoamer is 0.05% to 0.15% of the total material mass; the bactericide is a benzimidazole bactericide, and the amount of the bactericide is 0.05% to 0.15% of the total material mass.

[0017] On the other hand, the present invention also provides a method for preparing the acrylic emulsion for inorganic silicate coating, which is obtained by free radical polymerization of unsaturated carboxylic acid, soft monomer, hard monomer and functional monomer under the action of polymerizable emulsifier.

[0018] The method for preparing the acrylic emulsion for inorganic silicate coating specifically comprises the following steps:

[0019] (1) Preparation of emulsifier aqueous solution: Add water and polymerizable emulsifier into a pre-emulsification kettle and stir until the system becomes uniform and transparent to obtain an emulsifier aqueous solution. Take out a portion of the emulsifier aqueous solution and add it to the polymerization kettle;

[0020] (2) Preparation of pre-emulsion: Add unsaturated carboxylic acid, soft monomer, hard monomer, functional monomer and water to the pre-emulsification kettle containing the emulsifier aqueous solution, mix well to obtain pre-emulsion, and take out part of the pre-emulsion and add it to the polymerization kettle;

[0021] (3) Adding initiator: adding part of the initiator to the polymerization kettle, and adding part of the initiator to the pre-emulsification kettle, and keeping the remaining initiator for later use;

[0022] (4) Polymerization: Control the temperature of the polymerization kettle at 75-85°C until the system presents a light blue emulsion, slowly add the pre-emulsion, mix well, and then add the remaining initiator; then, raise the temperature to 83-87°C, and continue stirring at this temperature for 20-40 minutes; then, cool down to 60-70°C, add a supplementary reducing agent, and keep warm for 10-20 minutes; cool down to 40-50°C, add an inorganic alkali solution to adjust the pH value of the emulsion to 7-9, continue to add functional additives, and mix well to obtain an acrylic emulsion for inorganic silicate coatings.

[0023] Furthermore, a polymer protective glue may be added during the preparation of the emulsifier aqueous solution in step (1), and the polymer protective glue is added simultaneously with water and the polymerizable emulsifier.

[0024] The mass ratio of water to polymerizable emulsifier in step (1) is 5:1 to 10:1, and the water in step (2) accounts for 40% to 50% of the total mass of the pre-emulsion.

[0025] The emulsifier aqueous solution taken out to the polymerization kettle in the step (1) accounts for 1 / 5-1 / 3 of its total mass.

[0026] The pre-emulsified liquid taken out to the polymerization kettle in the step (2) accounts for 1 / 6-1 / 4 of its total mass.

[0027] The mass ratio of the initiator added to the polymerization kettle, the pre-emulsification kettle and the initiator added to the step (3) and the step (4) is 1:1.5-2.5:0.8-1.2; further, in order to improve the dissolution efficiency of the initiator, the initiator can be configured into an aqueous solution before being added, with a solubility of 15-25wt%.

[0028] In the step (4), the supplementary reducing agent is ascorbic acid, and its amount is 1 / 5-1 / 3 of the total amount of the initiator. Furthermore, in order to improve the polymerization conversion rate, the supplementary reducing agent can be configured into an aqueous solution with a concentration of 5-15wt%.

[0029] The inorganic alkaline solution in step (4) is potassium hydroxide or sodium hydroxide.

[0030] The acrylic emulsion for inorganic silicate coating of the present invention has the following beneficial effects:

[0031] (1) The acrylic emulsion prepared by the present invention uses a polymerizable emulsifier, which is covalently bonded to the polyacrylate molecular chain, thereby improving the stability of the acrylic emulsion particles and reducing the free emulsifier content in the system; the acrylic emulsion uses glycidyl methacrylate or glycidyl acrylate as a functional monomer, which contains epoxy groups that can undergo a ring-opening reaction with the carboxylate anion of the acrylic acid molecule under alkaline conditions to generate a cross-linked structure inside the emulsion particles, making the emulsion particle structure more compact and reducing the possibility of mutual agglomeration. The above-mentioned acrylic emulsion structural design enables the acrylic emulsion to exhibit excellent compatibility and storage stability in an inorganic silicate solution.

[0032] (2) The acrylic acid partial sodium salt added to the acrylic acid emulsion prepared by the present invention can be adsorbed on the surface of the acrylic acid emulsion particles, thereby improving the charge stability of the emulsion particles, thereby further improving the compatibility and storage stability of the acrylic acid emulsion in the inorganic silicate solution.

[0033] (3) In the polymerization process of the acrylic emulsion of the present invention, two approaches, namely, temperature aging and adding a supplementary reducing agent, are used to increase the emulsion monomer conversion rate and reduce the VOC content of the system; an inorganic alkaline solution is used to adjust the acidity and alkalinity of the system, thereby avoiding the unpleasant odor caused by ammonia water or small molecular amines, and improving the environmental friendliness of the prepared inorganic silicate coating.

[0034] (4) The acrylic emulsion of the present invention can form a hard coating with silicate and silica sol without adding a film-forming aid; the prepared inorganic silicate coating has good thermal stability and can still effectively form a film after being stored at high temperature for 2 months, and the properties of the coating film can still meet the requirements of various indicators and meet the actual construction needs. DETAILED DESCRIPTION

[0035] Below in conjunction with the embodiment of the present invention, the technical scheme of the present invention is clearly and completely described. Obviously, the described embodiment is only a part of the embodiment of the present invention, rather than all the embodiments. Based on the embodiment in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not indicate specific conditions in the embodiment of the present invention are carried out according to the conditions recommended by normal conditions or manufacturers. Those who do not indicate the manufacturer of reagents or instruments used in the embodiment are all conventional products that can be obtained by commercial purchase.

[0036] In the examples and comparative examples, the polymerizable emulsifier DNS-86 for preparing the acrylic emulsion for inorganic silicate coatings was produced by Hanke Chemical, the polymerizable emulsifier MAX-100 was produced by Liaoning Kelong Fine Chemical Co., Ltd., the mineral oil defoamer was Solvay Rhodoline DF642 NI, the silicone defoamer was BASF FoamStar SI 2210, and the benzimidazole fungicide was Kaitai Bio-Carbendazim CTB-DJL.

[0037] Example 1

[0038] Preparation of S01 emulsifier aqueous solution: add 13g water, 2g DNS-86 and 1g polyacrylic acid partial sodium salt into a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain the emulsifier aqueous solution; take 4g of the emulsifier aqueous solution and add it into the polymerization kettle.

[0039] Preparation of S02 pre-emulsion: 3g acrylic acid (AA), 20g butyl acrylate (BA), 2g octyl acrylate (EHA), 25g styrene (St), 2g glycidyl methacrylate (GMA) and 33g water were added to the pre-emulsification kettle with 12g emulsifier solution remaining, and stirred at a low speed for 30 minutes to obtain the pre-emulsion. Subsequently, 1 / 5 of the total amount of the pre-emulsion was added to the polymerization kettle.

[0040] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0041] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0042] S05 Discharging: Add 0.1g of silicone defoamer and 0.1g of benzimidazole fungicide to the emulsion, stir evenly and filter the discharging.

[0043] Example 2

[0044] Preparation of S01 emulsifier aqueous solution: add 20.5g water, 2.5g MAX-100 and 1g polyacrylic acid partial sodium salt into a pre-emulsification kettle equipped with a stirrer, stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 6g of the emulsifier solution and add it into the polymerization kettle.

[0045] Preparation of S02 pre-emulsion: 4.5g acrylic acid, 20g butyl acrylate, 3g octyl acrylate, 38g styrene, 2g glycidyl methacrylate and 38g water were added to the pre-emulsification kettle with 18g emulsifier solution remaining, and stirred at low speed for 30 minutes to obtain pre-emulsion. Subsequently, 1 / 5 of the total amount of pre-emulsion was added to the polymerization kettle.

[0046] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0047] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0048] S05 Discharging: Add 0.1g mineral oil defoamer and 0.1g benzimidazole fungicide to the emulsion, stir evenly and filter the material.

[0049] Example 3

[0050] Preparation of S01 emulsifier aqueous solution: add 13g water, 2g DNS-86 and 1g polyacrylic acid partial sodium salt to a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 4g of the emulsifier solution and add it to the polymerization kettle.

[0051] Preparation of S02 pre-emulsion: 3g acrylic acid, 20g butyl acrylate, 2g octyl acrylate, 25g styrene, 2g glycidyl acrylate (GA) and 33g water were added to the pre-emulsification kettle with 12g emulsifier solution remaining, and stirred at low speed for 30 minutes to obtain pre-emulsion. Subsequently, 1 / 5 of the total amount of pre-emulsion was added to the polymerization kettle.

[0052] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0053] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0054] S05 Discharging: Add 0.1g mineral oil defoamer and 0.1g benzimidazole fungicide to the emulsion, stir evenly and filter the material.

[0055] Example 4

[0056] Preparation of S01 emulsifier aqueous solution: add 13g water, 2g DNS-86 and 1g polyacrylic acid partial sodium salt to a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 4g of the emulsifier solution and add it to the polymerization kettle.

[0057] Preparation of S02 pre-emulsion: 3g acrylic acid, 22g butyl acrylate, 25g styrene, 2g glycidyl methacrylate and 33g water were added to the pre-emulsification kettle with 12g emulsifier solution remaining, and stirred at a low speed for 30 minutes to obtain the pre-emulsion. Subsequently, 1 / 5 of the total amount of the pre-emulsion was added to the polymerization kettle.

[0058] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0059] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0060] S05 Discharging: Add 0.1g of silicone defoamer and 0.1g of benzimidazole fungicide to the emulsion, stir evenly and filter the discharging.

[0061] Example 5

[0062] Preparation of S01 emulsifier aqueous solution: add 13g water, 2g DNS-86 and 1g polyacrylic acid partial sodium salt to a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 4g of the emulsifier solution and add it to the polymerization kettle.

[0063] Preparation of S02 pre-emulsion: 1.5 g acrylic acid, 25 g butyl acrylate, 22 g styrene, 2 g glycidyl methacrylate and 33 g water were added to the pre-emulsification kettle with 12 g emulsifier solution remaining, and stirred at a low speed for 30 minutes to obtain the pre-emulsion. Subsequently, 1 / 5 of the total amount of the pre-emulsion was added to the polymerization kettle.

[0064] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0065] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0066] S05 Discharging: Add 0.1g of silicone defoamer and 0.1g of benzimidazole fungicide to the emulsion, stir evenly and filter the discharging.

[0067] Example 6

[0068] Preparation of S01 emulsifier aqueous solution: add 13g water, 2g DNS-86 and 1g polyacrylic acid partial sodium salt to a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 4g of the emulsifier solution and add it to the polymerization kettle.

[0069] Preparation of S02 pre-emulsion: 3g acrylic acid, 35g butyl acrylate, 28g styrene, 2g glycidyl methacrylate and 40g water were added to the pre-emulsification kettle with 12g emulsifier solution remaining, and stirred at a low speed for 30 minutes to obtain the pre-emulsion. Subsequently, 1 / 5 of the total amount of the pre-emulsion was added to the polymerization kettle.

[0070] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0071] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0072] S05 Discharging: Add 0.1g of silicone defoamer and 0.1g of benzimidazole fungicide to the emulsion, stir evenly and filter the discharging.

[0073] Example 7

[0074] Preparation of S01 emulsifier aqueous solution: add 13g water and 2g DNS-86 to a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain the emulsifier aqueous solution; take 3g of the emulsifier aqueous solution and add it to the polymerization kettle.

[0075] Preparation of S02 pre-emulsion: 3g acrylic acid (AA), 20g butyl acrylate (BA), 2g octyl acrylate (EHA), 25g styrene (St), 2g glycidyl methacrylate (GMA) and 33g water were added to the pre-emulsification kettle with 12g emulsifier solution remaining, and stirred at a low speed for 30 minutes to obtain the pre-emulsion. Subsequently, 1 / 5 of the total amount of the pre-emulsion was added to the polymerization kettle.

[0076] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0077] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2g of potassium hydroxide aqueous solution, adjust the pH to 7-9, stir evenly and filter out the material.

[0078] Comparative Example 1

[0079] This comparative example is set based on Example 3, except that the polymerizable emulsifier selected in the present invention is not used.

[0080] Preparation of S01 emulsifier aqueous solution: add 13g water, 1.4g sodium dodecyl sulfate, 0.7g alkylphenol polyoxyethylene ether OP-10 and 1g polyacrylic acid partial sodium salt into a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 4g of the emulsifier solution and add it to the polymerization kettle.

[0081] Preparation of S02 pre-emulsion: 3g acrylic acid, 20g butyl acrylate, 2g octyl acrylate, 25g styrene, 2g glycidyl acrylate (GA) and 33g water were added to the pre-emulsification kettle with 12g emulsifier solution remaining, and stirred at low speed for 30 minutes to obtain pre-emulsion. Subsequently, 1 / 5 of the total amount of pre-emulsion was added to the polymerization kettle.

[0082] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0083] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of potassium hydroxide aqueous solution, and adjust the pH to 7-9.

[0084] S05 Discharging: Add 0.1g of silicone defoamer and 0.1g of benzimidazole fungicide to the emulsion, stir evenly and filter the discharging.

[0085] Comparative Example 2

[0086] This comparative example is based on Example 4, except that no functional monomer is added.

[0087] Preparation of S01 emulsifier aqueous solution: add 13g water, 2g DNS-86 and 1g polyacrylic acid partial sodium salt to a pre-emulsification kettle equipped with a stirrer, and stir at a low speed until the system becomes uniform and transparent to obtain an emulsifier solution; take 4g of the emulsifier solution and add it to the polymerization kettle.

[0088] Preparation of S02 pre-emulsion: 3g acrylic acid, 22g butyl acrylate, 25g styrene and 33g water were added to the pre-emulsification kettle with 12g emulsifier solution left, and stirred at low speed for 30 minutes to obtain pre-emulsion. Subsequently, 1 / 5 of the total amount of pre-emulsion was added to the polymerization kettle.

[0089] Preparation of S03 initiator aqueous solution: Dissolve 0.4g of ammonium persulfate in 2g of water and stir until completely dissolved to obtain an initiator aqueous solution. Subsequently, add 0.6g of the initiator aqueous solution to the polymerization kettle, and add 1.2g of the initiator aqueous solution to the pre-emulsification kettle, leaving 0.6g of the initiator aqueous solution for later use. In addition, dissolve 0.1g of ascorbic acid in 1g of water for later use.

[0090] S04 polymerization: heat the polymerization kettle to 75-80°C and continue stirring at this temperature for 30 minutes until the system presents a light blue emulsion; then, add the pre-emulsion dropwise at a uniform rate and complete the addition within 180 minutes; add 0.6 g of the reserved initiator aqueous solution to the polymerization kettle; then, heat to 84-86°C and continue stirring at this temperature for 30 minutes; then, cool to 70°C, add ascorbic acid aqueous solution, and keep warm for 15 minutes; cool to 45°C, add about 2 g of sodium hydroxide aqueous solution, and adjust the pH to 7-9.

[0091] S05 Discharging: Add 0.1g of silicone defoamer and 0.1g of benzimidazole fungicide to the emulsion, stir evenly and filter the discharging.

[0092] Application Examples

[0093] According to the national standard GB / T 20623-2006 "Emulsions for architectural coatings", the present invention performs performance tests on the acrylic emulsions prepared in Examples 1-7 and Comparative Examples 1-2, and the characterization results are shown in Table 1. As can be seen from Table 1, the prepared acrylic emulsion for inorganic silicate coatings is a white emulsion with a light blue hue, the content of long alkyl chain octyl acrylate has a greater influence on the viscosity of the acrylic emulsion for inorganic silicate coatings, and the mechanical stability, thermal stability and chemical stability can all meet actual requirements.

[0094] Table 1 Performance test results of acrylic emulsions prepared in Examples 1-7 and Comparative Examples 1-2

[0095]

[0096]

[0097] The compatibility of the acrylic emulsions prepared in Examples 1-7 of the present invention and Comparative Examples 1-2 with potassium silicate and silica sol was tested by the following method: 1 part of acrylic emulsion was slowly added dropwise to 2 parts of silica sol JN30, and after stirring evenly, 3 parts of potassium silicate K39 were slowly added dropwise, and the agglomeration and viscosity change of the mixed system were observed. The characterization results are shown in Table 2.

[0098] Table 2 Viscosity test results of acrylic emulsions prepared in Examples 1-7 and Comparative Examples 1-2

[0099]

[0100] The acrylic emulsions prepared in Examples 1-7 and Comparative Examples 1-2 are applied to inorganic silicate exterior wall coatings, wherein the mass fraction of each component, based on the total weight of the inorganic coating, is: 8wt% acrylic emulsion, 15wt% potassium silicate K39, 10wt% silica sol JN30, 15wt% titanium dioxide, 8wt% heavy calcium carbonate, 0.5wt% dispersant, 0.3wt% defoamer, 0.3wt% pH regulator, 0.8wt% hydroxyethyl cellulose, 0.5wt% bentonite, 0.5wt% quaternary ammonium salt stabilizer, and deionized water so that the total amount reaches 100%. The preparation steps are as follows: adding part of deionized water into a dispersion tank, adjusting the rotation speed to 300-500 r / min, adding hydroxyethyl cellulose, stirring until it is evenly dissolved, increasing the rotation speed to 600-800 r / min, adding a dispersant, a defoamer, and a pH regulator, and continuing to stir for 5-10 minutes; adding titanium dioxide, heavy calcium carbonate and bentonite, adjusting the rotation speed to 1000-1300 r / min, stirring for 15-20 minutes until it is evenly dispersed, and after the stirring is completed, the scraper test fineness is ≤50 microns; adjusting the rotation speed to 800-1000 r / min, adding silica sol, acrylic emulsion, potassium silicate and a stabilizer in sequence, stirring for 5-10 minutes, and discharging the material to obtain an inorganic silicate exterior wall coating. Subsequently, the physical and chemical properties of the configured inorganic silicate exterior wall coatings were measured with reference to the industry standard JG / T26-2002 "Inorganic architectural coatings for exterior walls", such as heat storage stability, freeze-thaw stability (3 times), scrub resistance, water resistance, alkali resistance, temperature change resistance, stain resistance and artificial aging resistance. The adhesion was measured with reference to the standard GB / T 9286-1998 "Scratch test for paint and varnish films", and the coating hardness was measured with reference to the standard GB / T 6739-2006 "Paints and varnishes: Determination of film hardness by pencil method". The performance characterization data are shown in Table 3.

[0101] Table 3 Key performance data of inorganic exterior wall coating samples

[0102]

[0103] The characterization results of the above embodiments and comparative examples show that the acrylic emulsion prepared by the present invention has good compatibility with potassium silicate and silica sol; the comparison of the performance evaluation results of the inorganic coating prepared by the acrylic emulsion prepared by Example 3 and Comparative Example 1 shows that the emulsion prepared by the polymerizable emulsifier has higher stability and better performance advantages than the small molecule emulsifier; the performance evaluation results of the inorganic coating prepared by the acrylic emulsion prepared by Example 4 and Comparative Example 2 show that the functional monomer glycidyl methacrylate or glycidyl acrylate plays a key role therein.

[0104] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the above embodiments describe the present invention in detail, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An acrylic emulsion for inorganic silicate coating, characterized in that: The raw materials for its preparation include the following components by mass: Wherein, the functional monomer is an unsaturated glycidyl ether or an unsaturated glycidyl ester; The polymerizable emulsifier is one or a combination of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate, allyloxy isotridecyl alcohol polyoxyethylene ether sulfate ammonium salt or sodium acrylamide isopropyl sulfonate.

2. The acrylic emulsion for inorganic silicate coating according to claim 1, characterized in that: The raw materials for preparing the acrylic emulsion for inorganic silicate coating also include polymer protective glue.

3. The acrylic emulsion for inorganic silicate coating according to claim 2, characterized in that: The polymer protective glue is polyacrylic acid partial sodium salt, and the amount of the polymer protective glue is 0.5% to 1.5% of the total material mass.

4. The acrylic emulsion for inorganic silicate coating according to claim 1, characterized in that: The unsaturated carboxylic acid is selected from acrylic acid, methacrylic acid or a combination of both.

5. The acrylic emulsion for inorganic silicate coating according to claim 1, characterized in that: The soft monomer is selected from one or more combinations of ethyl acrylate, butyl acrylate, octyl acrylate and octyl methacrylate.

6. The acrylic emulsion for inorganic silicate coating according to claim 1, characterized in that: The hard monomer is selected from styrene, methyl methacrylate or a combination of both.

7. The acrylic emulsion for inorganic silicate coating according to claim 1, characterized in that: The initiator is a persulfate thermal initiator.

8. The acrylic emulsion for inorganic silicate coating according to claim 1, characterized in that: The functional auxiliary agent is one or more combinations of defoaming agents and bactericides.

9. The method for preparing the acrylic emulsion for inorganic silicate coating according to any one of claims 1 to 8, characterized in that: The specific steps include: (1) Preparation of emulsifier aqueous solution: Add water and polymerizable emulsifier into a pre-emulsification kettle and stir until the system becomes uniform and transparent to obtain an emulsifier aqueous solution. Take out a portion of the emulsifier aqueous solution and add it to the polymerization kettle; (2) Preparation of pre-emulsion: Add unsaturated carboxylic acid, soft monomer, hard monomer, functional monomer and water to the pre-emulsification kettle containing the emulsifier aqueous solution, mix well to obtain pre-emulsion, and take out part of the pre-emulsion and add it to the polymerization kettle; (3) Adding initiator: adding part of the initiator to the polymerization kettle, and adding part of the initiator to the pre-emulsification kettle, and keeping the remaining initiator for later use; (4) Polymerization: Control the temperature of the polymerization kettle at 75-85°C until the system presents a light blue emulsion, slowly add the pre-emulsion, mix well, and then add the remaining initiator; then, raise the temperature to 83-87°C, and continue stirring at this temperature for 20-40 minutes; then, cool down to 60-70°C, add a supplementary reducing agent, and keep warm for 10-20 minutes; cool down to 40-50°C, add an inorganic alkali solution to adjust the pH value of the emulsion to 7-9, continue to add functional additives, and mix well to obtain an acrylic emulsion for inorganic silicate coatings.

10. The preparation method according to claim 9, characterized in that: In the step (1), a polymer protective glue is also added during the preparation of the emulsifier aqueous solution. The polymer protective glue is added simultaneously with water and the polymerizable emulsifier.

11. The preparation method according to claim 9, characterized in that: The mass ratio of water to polymerizable emulsifier in step (1) is 5:1 to 10:1, and the water in step (2) accounts for 40% to 50% of the total mass of the pre-emulsion.

12. The preparation method according to claim 9, characterized in that: The emulsifier aqueous solution taken out to the polymerization kettle in step (1) accounts for 1 / 5-1 / 3 of its total mass; the pre-emulsified liquid taken out to the polymerization kettle in step (2) accounts for 1 / 6-1 / 4 of its total mass.

13. The preparation method according to claim 9, characterized in that: The mass ratio of the initiator added to the polymerization kettle and the pre-emulsification kettle in step (3) and the initiator added to step (4) is 1:1.5-2.5:0.8-1.

2.

14. The preparation method according to claim 9, characterized in that: In the step (4), the supplementary reducing agent is ascorbic acid, and its amount is 1 / 5-1 / 3 of the total amount of initiator.

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