Associative emulsion thickener for latex paint and preparation method thereof

Abstract

The invention relates to the technical field of coatings, in particular to an associative emulsion thickener for latex paint and a preparation method of the associative emulsion thickener. The associative emulsion thickener for the latex paint is formed by polymerizing a monomer A, a monomer B and a monomer C, the monomer A is prepared from tridecyl methacrylate, diethyl itaconate and isobornyl acrylate; the monomer B comprises methyl acrylate, acrylic acid and acrylic acid-2-hydroxyethyl ester; the monomer C is prepared from diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate. The thickening agent has the advantages of environmental protection, high biocompatibility and good thickening effect, solves the problem of poor stability of latex paint at low temperature and high temperature, and improves the glossiness.

Description

Technical Field

[0001] The present invention relates to the technical field of coatings, and more specifically to an associative emulsion thickener for latex paint and a preparation method thereof. Background Art

[0002] Latex paint is a mixture of high molecular polymer water dispersion and pigment and filler water dispersion. It is widely used in environmentally friendly coatings for housing construction because of its advantages such as fast film-forming speed, strong hiding power, environmental protection, no odor, and washability.

[0003] Thickeners can not only adjust the viscosity of latex paint and prevent sagging during construction, but also give the paint excellent mechanical properties and storage stability. They are an indispensable additive for latex paint. Inorganic thickeners for latex paint, such as bentonite, rely on the powder to absorb water and swell to produce suspension, resulting in strong thixotropy and poor leveling effect. Cellulose thickeners, such as hydroxyethyl cellulose, have the advantages of good thickening effect and good storage stability, but their leveling fluidity and anti-splashing properties are poor.

[0004] Associative thickeners can interact with particles or molecules in latex paint through intermolecular interactions such as hydrogen bonds and van der Waals forces to form a three-dimensional structure; they form micellar structures in the water phase; they have a certain spatial repulsion effect, etc., which improves the rheological properties of latex paint, increases the viscosity and consistency of latex paint, and thus achieves a thickening effect.

[0005] For example, the Chinese patent with publication number CN108299608A discloses an alkali-swellable associative thickener, which is prepared from the following components in mass percentage: 10%-15% methacrylic acid, 15%-20% ethyl acrylate, 0.1%-5% polyurea crosslinking monomer, 0.1%-3% hydrophobic associative monomer, 0.5%-2% anionic surfactant, 0.2%-0.1% nonionic surfactant, 0.1%-1% initiator, and the balance of deionized water. The alkali-swellable associative thickener of this technical solution is not easily affected by the amount of residual solvent in the aqueous system, auxiliary agents such as dispersants, and the ion concentration of the system, and has good stability.

[0006] Chinese patent publication number CN1840588A discloses a method for preparing an associative thickener for latex paint. The main feature of the method is to introduce an associative monomer during the reaction of reactants polyethylene glycol and diisocyanate to enhance the associative ability of the thickener, so that the original two-point or single-point association is changed to a multi-point association of more than three points. The multi-point associated thickener and latex particles form a network structure, which has a good anchoring force on the color and filler particles, and solves the problem that the color and filler particles are easy to fall off when the latex paint using traditional water-based thickeners is stored, causing the stratification of the latex paint.

[0007] However, the above technical solutions all use a large amount of fossil resources, and the catalysts used, such as dibutyltin dilaurate and azobisisobutyronitrile, are toxic and irritating, and can also cause environmental pollution.

[0008] In addition, although the existing thickeners can make latex paint have good stability, they are prone to increase in viscosity in low temperature environments and to stratification or increased fluidity in high temperature environments. Summary of the invention

[0009] The present invention aims to provide an associative emulsion thickener for latex paint and a preparation method thereof in view of the deficiencies in the prior art. The thickener of the present invention is environmentally friendly, has high biocompatibility, and has a good thickening effect, so that the latex paint has good stability at both low and high temperatures and has good gloss.

[0010] The first aspect of the present invention provides an associative emulsion thickener for latex paint, wherein the associative emulsion thickener for latex paint is prepared by polymerization of monomer A, monomer B and monomer C; The monomer A comprises tridecyl methacrylate, diethyl itaconate and isobornyl acrylate, and the mass ratio of tridecyl methacrylate, diethyl itaconate and isobornyl acrylate is (3-5):1:(7-9); The monomer B comprises methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, and the mass ratio of the methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate is (1-2): (4-8): 1; The monomer C includes diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate, and the mass ratio of diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is (10-14):(4-6):(6-10):1.

[0011] In the present invention, when monomer C includes diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate, and the mass ratio of diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is controlled to be (10-14): (4-6): (6-10): 1, the obtained thickener not only has excellent thickening property, but also can prevent the styrene acrylic emulsion from thickening at low temperature and thinning at high temperature when it is applied to latex paint, especially styrene acrylic emulsion, so that the styrene acrylic emulsion can be stably present at -10°C and 50°C. The inventors speculate that it is because the diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate of the present invention are copolymerized with monomer A and monomer B. At low temperatures, the thickener can be combined with the particles in the styrene-acrylic emulsion by competitive adsorption and split the network structure, thereby reducing the viscosity of the styrene-acrylic emulsion; at high temperatures, the side chain can be amphiphilic, and hydrophobic association occurs between molecules to form physical crosslinks, thereby preventing the styrene-acrylic emulsion from becoming thinner. At the same time, the monomer C at this mass ratio can avoid random copolymerization between its monomers to affect the hydrophobic association performance of the side chain, and avoid the strength of the physical network structure formed, so that it has excellent thickening properties at low content.

[0012] The inventors have found that when a thickener obtained by using the specific monomer C of the present invention is used in a styrene-acrylic emulsion, although the thickener can avoid being sticky at low temperatures, it has poor high temperature resistance and is prone to stratification at high temperatures for a long time. The inventors have unexpectedly found through a large number of experiments that when the monomer B includes methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, and the mass ratio of methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate is controlled to be (1-2): (4-8): 1, the thickener obtained can avoid being stratified at high temperatures for a long time when used in a styrene-acrylic emulsion. The inventors speculate that this is because the specific monomer B can improve the rigidity of the thickener molecule, making it have better high temperature resistance, and can also inhibit the hydrolysis reaction of the amide group in the monomer C, thereby avoiding stratification of the styrene-acrylic emulsion at high temperatures for a long time.

[0013] Preferably, the tridecyl methacrylate and isobornyl acrylate are both of biological origin.

[0014] Preferably, the associative emulsion thickener for latex paint comprises, by weight, 100 parts of monomer A, 15-25 parts of monomer B, 5-15 parts of monomer C, 3-15 parts of emulsifier, 0.01-0.5 parts of initiator and 150-300 parts of water.

[0015] Preferably, the associative emulsion thickener for latex paint comprises, by weight, 100 parts of monomer A, 18-22 parts of monomer B, 6-10 parts of monomer C, 5-10 parts of emulsifier, 0.01-0.2 parts of initiator and 200-250 parts of water.

[0016] The inventors found that, while using specific monomers B and C to solve the problem of temperature resistance of the thickener, by controlling the mass ratio of monomer A, monomer B and monomer C to 100:(18-22):(6-10), the obtained thickener can also improve the gloss of the styrene-acrylic emulsion when used in styrene-acrylic emulsion. The inventors speculate that this is because the thickener polymerized under this condition can avoid the stratification of fillers in the styrene-acrylic emulsion, the fillers in the styrene-acrylic emulsion are more uniform during construction, and a denser and smoother coating film can be formed when drying, thereby improving the gloss.

[0017] Preferably, the emulsifier comprises a nonionic emulsifier and an anionic emulsifier, and the mass ratio of the nonionic emulsifier to the anionic emulsifier is (2-4):1.

[0018] Preferably, the nonionic emulsifier is plant polyphenol polyoxyethylene polyoxypropylene ether.

[0019] Preferably, the anionic emulsifier is plant polyphenol polyoxyethylene ether ammonium sulfate.

[0020] The present invention unexpectedly discovered that when plant polyphenol polyoxyethylene polyoxypropylene ether and plant polyphenol polyoxyethylene ether ammonium sulfate are compounded for use, synergistic enhancement can be achieved to improve the thickening effect and stability of the thickener.

[0021] Preferably, the initiator is selected from at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0022] The second aspect of the present invention provides a method for preparing an associative emulsion thickener for latex paint, comprising the following steps: S1, placing 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water in a reaction container, and stirring evenly to obtain a first mixture; S2, mixing monomer A, monomer B, 1 / 2 mass of initiator, 1 / 3 mass of emulsifier and 1 / 3 mass of water to obtain a second mixture; S3, adding monomer C, 1 / 3 of the mass of emulsifier and 1 / 3 of the mass of water to the second mixture and mixing to obtain a third mixture; S4, dropping the third mixture into the first mixture, raising the temperature to 50-60° C., and maintaining the temperature under stirring for reaction 3 to obtain the product.

[0023] Preferably, the time for dripping the third mixture into the first mixture in S4 is 1.5-2 hours.

[0024] Preferably, the insulation reaction time in S4 is 3-4 hours.

[0025] Beneficial Effects

[0026] 1. In the present invention, when monomer B includes methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, and the mass ratio of methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate is controlled to be (1-2):(4-8):1, the obtained enhancer can avoid stratification when used in styrene acrylic emulsion under long-term high temperature.

[0027] 2. In the present invention, when monomer C includes diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate, and the mass ratio of diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is controlled to be (10-14): (4-6): (6-10): 1, the obtained thickener not only has excellent thickening property, but also when it is applied to latex paint, especially styrene acrylic emulsion, it can prevent the styrene acrylic emulsion from thickening at low temperature and thinning at high temperature, so that the styrene acrylic emulsion can be stably present at -10°C and 50°C.

[0028] 3. The present invention adopts specific monomers B and C to solve the problem of temperature resistance of the thickener. By controlling the mass ratio of monomer A, monomer B and monomer C to 100:(18-22):(6-10), the obtained thickener can also improve the gloss of styrene-acrylic emulsion when used in styrene-acrylic emulsion.

[0029] 4. When the plant polyphenol polyoxyethylene polyoxypropylene ether and the plant polyphenol polyoxyethylene ether ammonium sulfate are compounded and used, synergistic enhancement can be achieved to improve the thickening effect and stability of the thickener.

[0030] 5. The technical solution of the present invention is to copolymerize monomers prepared from renewable resources and monomers with specific functions, which is more environmentally friendly and can solve the problem of unstable performance of traditional thickeners under specific conditions. DETAILED DESCRIPTION

[0031] In order to better explain the present invention, the technical scheme in the embodiments of the present invention will be clearly and completely described below in conjunction with the examples in the embodiments of the present invention. The embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other implementation methods obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. The experimental methods in the following embodiments, unless otherwise specified, are conventional methods, and the materials, reagents, etc. used in the following embodiments, unless otherwise specified, can be obtained from commercial channels.

[0032] Example 1

[0033] An associative emulsion thickener for latex paint, wherein the raw materials of the associative emulsion thickener for latex paint include 100 parts of monomer A, 25 parts of monomer B, 15 parts of monomer C, 15 parts of emulsifier, 0.5 parts of initiator and 300 parts of water in parts by mass; The monomer A comprises tridecyl methacrylate, diethyl itaconate and isobornyl acrylate, and the mass ratio of tridecyl methacrylate, diethyl itaconate and isobornyl acrylate is 4:1:8; The monomer B comprises methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, and the mass ratio of the methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate is 1:6:1; The monomer C includes diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate, and the mass ratio of the diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is 12:5:8:1.

[0034] The tridecyl methacrylate was purchased from VISIOMER, model number: Terra C13-MA; the isobornyl acrylate was purchased from VISIOMER, model number: IBOA.

[0035] The emulsifier comprises a nonionic emulsifier and an anionic emulsifier, and the mass ratio of the nonionic emulsifier to the anionic emulsifier is 3:1.

[0036] The nonionic emulsifier is plant polyphenol polyoxyethylene polyoxypropylene ether, purchased from Changshu Naisu Biomaterial Technology Co., Ltd., model: MSS1305.

[0037] The anionic emulsifier is plant polyphenol polyoxyethylene ether ammonium sulfate, purchased from Changshu Naisu Biomaterial Technology Co., Ltd., model: NSN3522.

[0038] The initiator is ammonium persulfate.

[0039] A method for preparing an associative emulsion thickener for latex paint comprises the following steps: S1, placing 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water in a reaction container, and stirring evenly to obtain a first mixture; S2, mixing monomer A, monomer B, 1 / 2 mass of initiator, 1 / 3 mass of emulsifier and 1 / 3 mass of water to obtain a second mixture; S3, adding monomer C, 1 / 3 of the mass of emulsifier and 1 / 3 of the mass of water to the second mixture and mixing to obtain a third mixture; S4, dropping the third mixture into the first mixture, raising the temperature to 50-60° C., and maintaining the temperature under stirring for reaction 3 to obtain the product.

[0040] The time for dripping the third mixture into the first mixture in S4 is 1.5 hours.

[0041] The heat preservation reaction time in S4 is 3.5h.

[0042] Example 2

[0043] The difference from Example 1 is that the raw materials of the associative emulsion thickener for latex paint include 100 parts of monomer A, 15 parts of monomer B, 5 parts of monomer C, 3 parts of emulsifier, 0.1 parts of initiator and 150 parts of water, calculated by mass, and the rest are the same.

[0044] Example 3

[0045] The difference from Example 1 is that the raw materials of the associative emulsion thickener for latex paint include 100 parts of monomer A, 20 parts of monomer B, 8 parts of monomer C, 8 parts of emulsifier, 0.2 parts of initiator and 220 parts of water, calculated by mass, and the rest are the same.

[0046] Comparative Example 1 The difference from Example 3 is that the monomer B includes methyl acrylate and acrylic acid, the mass ratio of methyl acrylate to acrylic acid is 1:6, and the rest are the same.

[0047] Comparative Example 2 The difference from Example 3 is that the mass ratio of methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate is 3:10:1, and the rest are the same.

[0048] Comparative Example 3 The difference from Example 3 is that the monomer C includes diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate; the mass ratio of diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is 12:5:1, and the rest are the same.

[0049] Comparative Example 4 The difference from Example 3 is that diacetone acrylamide is replaced by N,N-dimethyl acrylamide, and the rest is the same.

[0050] Comparative Example 5 The difference from Example 3 is that the mass ratio of diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is 8:7:5:1, and the rest are the same.

[0051] Comparative Example 6 The difference from Example 3 is that the emulsifier is a nonionic emulsifier, and the rest is the same.

[0052] Comparative Example 7 The difference from Example 3 is that the emulsifier is an anionic emulsifier, and the rest is the same.

[0053] Test Case The thickeners of Examples 1-3 and Comparative Examples 1-7 were applied to styrene-acrylic emulsions. The formula of the styrene-acrylic emulsions was based on the Chinese patent with the authorization announcement number CN101096475B. The formula is shown in Table 1 in terms of mass percentage.

[0054] Table 1 Formula of styrene acrylic emulsion

[0055] The following tests were performed on the styrene acrylic emulsions containing the thickeners of Examples 1-3 of the present invention and Comparative Examples 1-7: 1. Low temperature stability: Place in -5℃ environment for 30 days, return to room temperature, and observe whether there are lumps, agglomeration or separation. If any of these phenomena occur, it is considered unqualified. The results are shown in Table 2.

[0056] 2. High temperature stability: Place in a 50°C environment for 30 days, return to room temperature, and observe whether water separation or precipitation occurs. If either phenomenon occurs, it is recorded as unqualified. The results are shown in Table 2.

[0057] 3. The viscosity at different temperatures was measured using a viscometer. The results are shown in Table 3.

[0058] 4. Gloss: Add phthalocyanine blue slurry (Blue L116) in an amount of 0.5% of the total mass of the styrene acrylic emulsion, and apply it on the wall by roller coating with a thickness of 80µm. After the coating film has dried for 24 hours, use an intelligent three-angle gloss meter to measure and read the 60° angle reading. The results are shown in Table 3.

[0059] Table 2 Styrene-acrylic emulsion stability test results of thickeners of Examples 1-3 and Comparative Examples 1-7

[0060] It can be seen from Table 2 that the thickeners of Examples 1-3 can make the styrene acrylic emulsion have good low temperature stability and high temperature stability at the same time; In Comparative Example 1-2, due to the change in the composition of monomer B, the obtained thickener caused the high temperature stability of the styrene-acrylic emulsion to deteriorate significantly; In Comparative Example 3-5, due to the change in the composition of monomer C, the obtained thickener caused the high temperature stability of the styrene-acrylic emulsion to deteriorate significantly; In Comparative Example 6-7, due to the change in the composition of the emulsifier, the obtained thickener caused the low-temperature stability and high-temperature stability of the styrene-acrylic emulsion to deteriorate significantly.

[0061] Table 3 Viscosity and gloss test results of styrene acrylic emulsion thickeners of Examples 1-3 and Comparative Examples 1-7

[0062] It can be seen from Table 3 that: The thickeners of Examples 1-3 all have good thickening properties, preventing the styrene acrylic emulsion from thickening at low temperatures and thinning at high temperatures; however, Example 3 has the best glossiness.

[0063] In Comparative Example 1-2, due to the change in the composition of monomer B, the thickening property of the obtained thickener decreased, and the styrene-acrylic emulsion thickened at low temperatures and thinned at high temperatures, and the gloss decreased; In Comparative Example 3-5, due to the change in the composition of monomer C, the thickening property of the obtained thickener decreased, and the styrene acrylic emulsion thickened at low temperatures and thinned at high temperatures, and the gloss decreased; In Comparative Example 6-7, due to the change in the composition of the emulsifier, the thickening property of the obtained thickener decreased, and the styrene acrylic emulsion thickened at low temperatures and thinned at high temperatures, and the glossiness decreased.

[0064] The above description is only a specific embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent transformation made by the present invention, or directly or indirectly applied in other related technical fields, is also included in the patent protection scope of the present invention.

Claims

1. An associative emulsion thickener for latex paint, characterized in that: The associative emulsion thickener for latex paint is prepared by polymerization of monomer A, monomer B and monomer C; The monomer A comprises tridecyl methacrylate, diethyl itaconate and isobornyl acrylate, and the mass ratio of tridecyl methacrylate, diethyl itaconate and isobornyl acrylate is (3-5):1:(7-9); The monomer B comprises methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate, and the mass ratio of the methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate is (1-2): (4-8): 1; The monomer C includes diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide and ethylene glycol dimethacrylate, and the mass ratio of diacetone acrylamide, N-isopropyl acrylamide, N-isopropyl acrylamide and ethylene glycol dimethacrylate is (10-14):(4-6):(6-10):

1.

2. The associative emulsion thickener for latex paint according to claim 1, characterized in that: The associative emulsion thickener for latex paint comprises raw materials, by weight, including 100 parts of monomer A, 15-25 parts of monomer B, 5-15 parts of monomer C, 3-15 parts of emulsifier, 0.01-0.5 parts of initiator and 150-300 parts of water.

3. The associative emulsion thickener for latex paint according to claim 2, characterized in that: The associative emulsion thickener for latex paint comprises, by weight, 100 parts of monomer A, 18-22 parts of monomer B, 6-10 parts of monomer C, 5-10 parts of emulsifier, 0.01-0.2 parts of initiator and 200-250 parts of water.

4. The associative emulsion thickener for latex paint according to claim 3, characterized in that: The emulsifier includes a nonionic emulsifier and an anionic emulsifier, and the mass ratio of the nonionic emulsifier to the anionic emulsifier is (2-4):

1.

5. The associative emulsion thickener for latex paint according to claim 4, characterized in that: The nonionic emulsifier is plant polyphenol polyoxyethylene polyoxypropylene ether.

6. The associative emulsion thickener for latex paint according to claim 4, characterized in that: The anionic emulsifier is plant polyphenol polyoxyethylene ether ammonium sulfate.

7. The associative emulsion thickener for latex paint according to claim 2, characterized in that: The initiator is selected from at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

8. A method for preparing an associative emulsion thickener for latex paint according to any one of claims 2 to 7, characterized in that: The following steps are involved: S1, placing 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water in a reaction container, and stirring evenly to obtain a first mixture; S2, mixing monomer A, monomer B, 1 / 2 mass of initiator, 1 / 3 mass of emulsifier and 1 / 3 mass of water to obtain a second mixture; S3, adding monomer C, 1 / 3 of the mass of emulsifier and 1 / 3 of the mass of water to the second mixture and mixing to obtain a third mixture; S4, dripping the third mixture into the first mixture, raising the temperature to 50-60° C., and maintaining the temperature under stirring for reaction 3 to obtain.

9. The preparation method according to claim 8, characterized in that: The time for dripping the third mixture into the first mixture in S4 is 1.5-2 hours.

10. The preparation method according to claim 8, characterized in that: The heat preservation reaction time in S4 is 3-4h.

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