An associative emulsion thickener for latex paint and its preparation method

Abstract

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. The associative emulsion thickener for latex paint is polymerized from monomer A, monomer B and monomer C; monomer A includes tridecyl methacrylate, diethyl itaconate and isobornyl acrylate; monomer B includes methyl acrylate, acrylic acid and 2-hydroxyethyl acrylate; monomer C includes diacetone acrylamide, N-isopropylacrylamide, N-dodecylacrylamide and ethylene glycol dimethacrylate. The thickener of the present invention is environmentally friendly, has high biocompatibility, has good thickening effect, solves the problem of poor stability of latex paint at low and high temperatures, 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 a polymer polymer aqueous dispersion and a pigment and filler aqueous dispersion, and is widely used in environmentally friendly coatings for housing construction because of its advantages such as fast film formation speed, strong hiding power, environmental protection and no peculiar smell, and good washability.

[0003] The thickener can not only adjust the viscosity of the latex paint to prevent sagging during construction, but also endow the paint with excellent mechanical properties and storage stability, and is an indispensable auxiliary for latex paint. Inorganic thickeners for latex paint, such as bentonite, rely on powder to absorb water and expand to produce suspension, resulting in strong thixotropy of the latex paint and poor leveling effect; cellulose thickeners, such as hydroxyethyl cellulose, although having good thickening effect and good storage stability, have poor leveling fluidity and anti-splashing performance.

[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; form micelle structures in the aqueous phase; have a certain steric repulsion effect, etc., which improve the rheological properties of latex paint, increase the viscosity and consistency of latex paint, and thus achieve the thickening effect.

[0005] For example, Chinese Patent No. CN108299608A discloses an alkali-swellable associative thickener, which is prepared from the following components in mass percentages: 10%-15% of methacrylic acid, 15%-20% of ethyl acrylate, 0.1%-5% of polyurea cross-linking monomer, 0.1%-3% of hydrophobic associative monomer, 0.5%-2% of anionic surfactant, 0.2%-0.1% of non-ionic surfactant, 0.1%-1% of initiator, and the balance of deionized water. The alkali-swellable associative thickener of this technical solution is not easily affected by the residual solvent amount, auxiliaries such as dispersants, and the ionic concentration of the aqueous system, and has good stability.

[0006] Chinese Patent No. CN1840588A discloses a preparation method of an associative thickener for latex paint. The main feature of this method is to introduce an associative monomer during the reaction of reactants polyethylene glycol and diisocyanate to enhance the associative ability of the thickener, change the original two-point or single-point association to multi-point association of more than three points. The multi-point associative thickener forms a network structure with latex particles and has good anchoring force on pigment and filler particles, solving the problems that pigment and filler particles are easy to fall off during storage of latex paint using traditional water-based thickeners, resulting in stratification of 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 all toxic and irritating, and will also cause environmental pollution.

[0008] In addition, although the existing thickeners can make the latex paint have good stability, they are prone to an increase in viscosity in a low-temperature environment and are prone to delamination or an increase in fluidity in a high-temperature environment. Summary of the Invention

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

[0010] The first aspect of the present invention provides an associative emulsion thickener for latex paint, and the associative emulsion thickener for latex paint is polymerized from monomer A, monomer B, and monomer C;

[0011] The monomer A includes 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);

[0012] 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 (1 - 2):(4 - 8):1;

[0013] 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-dodecyl acrylamide, and ethylene glycol dimethacrylate is (10 - 14):(4 - 6):(6 - 10):1.

[0014] 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-dodecyl acrylamide, and ethylene glycol dimethacrylate is controlled to be (10 - 14):(4 - 6):(6 - 10):1, the obtained thickener not only has excellent thickening properties, but also can prevent the styrene-acrylic emulsion from thickening at low temperatures and thinning at high temperatures when it is applied to latex paints, especially styrene-acrylic emulsions, enabling the styrene-acrylic emulsion to stably exist at -10°C and 50°C. The inventor of the present invention conjectures that this is because the diacetone acrylamide, N-isopropyl acrylamide, N-dodecyl acrylamide, and ethylene glycol dimethacrylate of the present invention copolymerize with monomer A and monomer B. At low temperatures, the thickener can bind to the particles in the styrene-acrylic emulsion through competitive adsorption and disassemble the network structure, thereby reducing the viscosity of the styrene-acrylic emulsion; at high temperatures, the side chains can exhibit amphiphilicity, undergo intermolecular hydrophobic association, and form physical crosslinks, thereby preventing the styrene-acrylic emulsion from thinning. At the same time, monomer C with this mass ratio can avoid the random copolymerization between its monomers from affecting the hydrophobic association performance of the side chains and the strength of the physical network structure formed, so that it has excellent thickening properties at low contents.

[0015] The inventor of the present invention found that when the thickener obtained by using the specific monomer C of the present invention is used in styrene-acrylic emulsions, although it can prevent the emulsion from becoming viscous at low temperatures, its high-temperature persistence is poor and it is prone to delamination under long-term high temperatures. The inventor of the present invention unexpectedly found through a large number of experiments that 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 thickener can prevent the styrene-acrylic emulsion from delaminating under long-term high temperatures. The inventor of the present invention conjectures that this is because the specific monomer B can increase the rigidity of the thickener molecules, enabling it to have better high-temperature resistance while also inhibiting the hydrolysis reaction of the amide groups in monomer C, thereby preventing the styrene-acrylic emulsion from delaminating under long-term high temperatures.

[0016] Preferably, both tridecyl methacrylate and isobornyl acrylate are of biological origin.

[0017] Preferably, for the associative emulsion thickener for latex paints, by mass, the raw materials include 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.

[0018] Preferably, for the associative emulsion thickener for latex paint, by mass, the raw materials include 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 part of initiator, and 200 - 250 parts of water.

[0019] The inventors found that while using specific monomer B and monomer C to solve the heat resistance of the thickener, by controlling the mass ratio of monomer A, monomer B, and monomer C to 100:(18 - 22):(6 - 10), when the obtained thickener is used in styrene - acrylic emulsion, it can also improve the gloss of the styrene - acrylic emulsion. The inventors guessed that it is because the thickener polymerized under this condition can avoid the stratification of fillers in the styrene - acrylic emulsion. During construction, the fillers in the styrene - acrylic emulsion are relatively uniform, and when dried, it can form a denser and smoother coating film, improving the gloss.

[0020] Preferably, the emulsifier includes a non - ionic emulsifier and an anionic emulsifier, and the mass ratio of the non - ionic emulsifier to the anionic emulsifier is (2 - 4):1.

[0021] Preferably, the non - ionic emulsifier is polyoxyethylene polyoxypropylene ether of plant polyene phenol.

[0022] Preferably, the anionic emulsifier is ammonium polyoxyethylene ether sulfate of plant polyene phenol.

[0023] The present invention unexpectedly found that when polyoxyethylene polyoxypropylene ether of plant polyene phenol and ammonium polyoxyethylene ether sulfate of plant polyene phenol are used in combination, they can synergistically enhance the thickening effect and stability of the thickener.

[0024] Preferably, the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and sodium persulfate.

[0025] The second aspect of the present invention provides a preparation method of an associative emulsion thickener for latex paint, including the following steps:

[0026] S1. Put 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water into a reaction vessel, stir evenly to obtain a first mixture;

[0027] S2. Mix monomer A, monomer B, 1 / 2 of the mass of the initiator, 1 / 3 of the mass of the emulsifier, and 1 / 3 of the mass of water to obtain a second mixture;

[0028] S3. Add monomer C, 1 / 3 of the mass of the emulsifier, and 1 / 3 of the mass of water to the second mixture and mix to obtain a third mixture;

[0029] S4. Drop the third mixture into the first mixture, raise the temperature to 50 - 60 °C, and keep the reaction under stirring conditions to obtain the product.

[0030] Preferably, the time for dropping the third mixture into the first mixture in S4 is 1.5 - 2 h.

[0031] Preferably, the time for the heat preservation reaction in S4 is 3 - 4 h.

[0032] Beneficial effects:

[0033] 1. When monomer B in the present invention 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 thickener can avoid stratification when used in styrene - acrylic emulsion at high temperature for a long time.

[0034] 2. When monomer C in the present invention includes diacetone acrylamide, N - isopropyl acrylamide, N - dodecyl acrylamide, and ethylene glycol dimethacrylate, and the mass ratio of diacetone acrylamide, N - isopropyl acrylamide, N - dodecyl 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 avoid the styrene - acrylic emulsion from thickening at low temperature and thinning at high temperature when applied to latex paint, especially styrene - acrylic emulsion, so that the styrene - acrylic emulsion can stably exist at - 10 °C and 50 °C.

[0035] 3. While using specific monomer B and monomer C in the present invention to solve the heat - resistance of the thickener, by controlling the mass ratio of monomer A, monomer B, and monomer C to be 100:(18 - 22):(6 - 10), when the obtained thickener is used in styrene - acrylic emulsion, it can also improve the gloss of the styrene - acrylic emulsion.

[0036] 4. When phytopolyene phenol polyoxyethylene polyoxypropylene ether and phytopolyene phenol polyoxyethylene ether ammonium sulfate are used in combination in the present invention, they can synergistically enhance the efficiency and improve the thickening effect and stability of the thickener.

[0037] 5. The technical solution of the present invention copolymerizes 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. Specific embodiments

[0038] To better explain the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention in combination with the examples in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other implementation methods obtained by those skilled in the art without creative work belong to the scope of protection of the present invention. The experimental methods in the following embodiments are all conventional methods unless otherwise specified. The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0039] Example 1

[0040] An associative emulsion thickener for latex paint, the associative emulsion thickener for latex paint, by mass, the raw materials include 100 parts of monomer A, 25 parts of monomer B, 15 parts of monomer C, 15 parts of emulsifier, 0.5 part of initiator and 300 parts of water;

[0041] The monomer A includes tridecyl methacrylate, diethyl itaconate and isobornyl acrylate, and the mass ratio of tridecyl methacrylate, diethyl itaconate and isobornyl acrylate is 4:1:8;

[0042] 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 1:6:1;

[0043] 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-dodecyl acrylamide and ethylene glycol dimethacrylate is 12:5:8:1.

[0044] The tridecyl methacrylate is purchased from VISIOMER, model: Terra C13-MA; the isobornyl acrylate is purchased from VISIOMER, model: IBOA.

[0045] The emulsifier includes a non-ionic emulsifier and an anionic emulsifier, and the mass ratio of the non-ionic emulsifier to the anionic emulsifier is 3:1.

[0046] The non-ionic emulsifier is a plant polyene phenol polyoxyethylene polyoxypropylene ether, purchased from Changshu Naisu Biotech Co., Ltd., model: MSS1305.

[0047] The anionic emulsifier is ammonium plant polyene phenol polyoxyethylene ether sulfate, purchased from Changshu Naisu Biotech Co., Ltd., model: NSN3522.

[0048] The initiator described above is ammonium persulfate.

[0049] A preparation method of an associative emulsion thickener for latex paint, comprising the following steps:

[0050] S1. Place 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water in a reaction vessel, stir evenly to obtain a first mixture;

[0051] S2. Mix monomer A, monomer B, 1 / 2 of the mass of the initiator, 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water to obtain a second mixture;

[0052] S3. Add monomer C, 1 / 3 of the mass of the emulsifier and 1 / 3 of the mass of water to the second mixture and mix to obtain a third mixture;

[0053] S4. Drop the third mixture into the first mixture, raise the temperature to 50 - 60 °C, and keep the reaction under stirring conditions to obtain the product.

[0054] The time for dropping the third mixture into the first mixture in S4 is 1.5 h.

[0055] The time for the holding reaction in S4 is 3.5 h.

[0056] Example 2

[0057] The difference from Example 1 is that for the associative emulsion thickener for latex paint, calculated by mass parts, the raw materials include 100 parts of monomer A, 15 parts of monomer B, 5 parts of monomer C, 3 parts of emulsifier, 0.1 part of initiator and 150 parts of water, and the rest are the same.

[0058] Example 3

[0059] The difference from Example 1 is that for the associative emulsion thickener for latex paint, calculated by mass parts, the raw materials include 100 parts of monomer A, 20 parts of monomer B, 8 parts of monomer C, 8 parts of emulsifier, 0.2 part of initiator and 220 parts of water, and the rest are the same.

[0060] Comparative Example 1

[0061] The difference from Example 3 is that monomer B includes methyl acrylate and acrylic acid, and the mass ratio of methyl acrylate to acrylic acid is 1:6, and the rest are the same.

[0062] Comparative Example 2

[0063] 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.

[0064] Comparative Example 3

[0065] 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.

[0066] Comparative Example 4

[0067] The difference from Example 3 is that diacetone acrylamide is replaced by N,N-dimethyl acrylamide, and the rest are the same.

[0068] Comparative Example 5

[0069] 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.

[0070] Comparative Example 6

[0071] The difference from Example 3 is that the emulsifier is a non-ionic emulsifier, and the rest are the same.

[0072] Comparative Example 7

[0073] The difference from Example 3 is that the emulsifier is an anionic emulsifier, and the rest are the same.

[0074] Test Example

[0075] The thickeners of Examples 1-3 and Comparative Examples 1-7 were applied to styrene-acrylic emulsions. The formulation of the styrene-acrylic emulsion refers to the Chinese patent with the authorized announcement number CN101096475B. By mass percentage, the formulation is specifically shown in Table 1.

[0076] Table 1 Formulation of Styrene-Acrylic Emulsion

[0077]

[0078] The following tests were carried out on the styrene-acrylic emulsions containing the thickeners of Examples 1-3 and Comparative Examples 1-7 of the present invention:

[0079] 1. Low-temperature stability: Place it in an environment of -5°C for 30 days, and then return it to room temperature. Observe whether there are hard lumps, coagulation or separation phenomena. If any of these phenomena occur, it is recorded as unqualified. The results are shown in Table 2.

[0080] 2. High-temperature stability: Place it in an environment of 50°C for 30 days, and then return it to room temperature. Observe whether there is water separation or precipitation phenomena. If any of these phenomena occur, it is recorded as unqualified. The results are shown in Table 2.

[0081] 3. Use a viscometer to measure the viscosity at different temperatures, and the results are shown in Table 3.

[0082] 4. Glossiness: Add 0.5% of phthalocyanine blue paste (Blue L116) based on the total mass of the styrene-acrylic emulsion to the styrene-acrylic emulsion. Apply it on the wall by roller coating with a thickness of 80 µm. After the coating film dries for 24 hours, use an intelligent three-angle gloss meter to measure and read the 60° angle reading, and the results are shown in Table 3.

[0083] Table 2 Test results of the stability of styrene-acrylic emulsion with thickeners for Examples 1-3 and Comparative Examples 1-7

[0084]

[0085] It can be seen from Table 2 that: The thickeners in Examples 1-3 can make the styrene-acrylic emulsion have good low-temperature stability and high-temperature stability at the same time;

[0086] In Comparative Examples 1-2, due to the change in the composition of monomer B, the obtained thickener causes the high-temperature stability of the styrene-acrylic emulsion to deteriorate significantly;

[0087] In Comparative Examples 3-5, due to the change in the composition of monomer C, the obtained thickener causes the high-temperature stability of the styrene-acrylic emulsion to deteriorate significantly;

[0088] In Comparative Examples 6-7, due to the change in the composition of the emulsifier, the obtained thickener causes both the low-temperature stability and the high-temperature stability of the styrene-acrylic emulsion to deteriorate significantly.

[0089] Table 3 Test results of the viscosity and glossiness of styrene-acrylic emulsion with thickeners for Examples 1-3 and Comparative Examples 1-7

[0090]

[0091] It can be seen from Table 3 that:

[0092] The thickeners in Examples 1-3 all have good thickening properties, avoiding the thickening of the styrene-acrylic emulsion at low temperatures and thinning at high temperatures; however, Example 3 has the best glossiness.

[0093] In Comparative Examples 1-2, due to the change in the composition of monomer B, the thickening property of the obtained thickener decreases, and the styrene-acrylic emulsion shows thickening at low temperatures and thinning at high temperatures, and the glossiness decreases;

[0094] In Comparative Examples 3-5, due to the change in the composition of monomer C, the thickening property of the obtained thickener decreases, and the styrene-acrylic emulsion shows thickening at low temperatures and thinning at high temperatures, and the glossiness decreases;

[0095] In Comparative Examples 6-7, due to the change in the composition of the emulsifier, the thickening property of the obtained thickener decreases, and the styrene-acrylic emulsion shows thickening at low temperatures and thinning at high temperatures, and the glossiness decreases.

[0096] The above are only specific embodiments of the present invention, and do not limit the patent scope of the present invention accordingly. Any equivalent transformation made by using the present invention, or directly or indirectly applied in other related technical fields, shall be similarly included in the patent protection scope of the present invention.

Claims

1. An associative emulsion thickener for latex paint, characterized in that, By mass parts, the raw materials are composed of 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; The monomer A includes 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 includes methyl acrylate, acrylic acid and 2 - hydroxyethyl acrylate, and the mass ratio of 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 - dodecyl acrylamide and ethylene glycol dimethacrylate is (10 - 14):(4 - 6):(6 - 10):1; The emulsifier includes non - ionic emulsifier and anionic emulsifier, and the mass ratio of non - ionic emulsifier to anionic emulsifier is (2 - 4):1; The non - ionic emulsifier is plant polyene phenol polyoxyethylene polyoxypropylene ether; the anionic emulsifier is plant polyene phenol polyoxyethylene ether ammonium sulfate.

2. The associative emulsion thickener for latex paint according to claim 1, wherein The associative emulsion thickener for latex paint, by mass parts, the raw materials are composed of 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.

3. The associative emulsion thickener for latex paint according to claim 1, wherein The initiator is selected from at least one of ammonium persulfate, potassium persulfate and sodium persulfate.

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