CN109734836B - Acrylate microgel emulsion and preparation method and application thereof - Google Patents
Acrylate microgel emulsion and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses an acrylate microgel emulsion and a preparation method and application thereof. The emulsion is prepared from a first raw material comprising the following components: 200-300 parts of water, 70-100 parts of alkyl (meth) acrylate, 8-15 parts of vinyl aromatic compound, 8-15 parts of hydroxyalkyl (meth) acrylate, 6-12 parts of unsaturated monomer containing two ethylenic bonds, 1-5 parts of initiator and 15-38 parts of emulsifier. The emulsion of the invention has lower production cost and can improve the sagging resistance of a paint film.
Description
Technical Field
The invention relates to an acrylate microgel emulsion, a preparation method and application thereof.
Background
The microgel generally represents particles having a particle size of 1 to 1000nm and an intramolecular cross-linked structure. The microgels are comparable in size to linear polymers of very high molecular weight, and are similar in size to sterically networked crosslinked polymers. The microgel has excellent functions due to the unique molecular structure, and can improve the sagging resistance of the coating. At present, the coating is developed towards the direction of high solid content and low solvent volatilization, so the research of microgel is paid attention to.
The submicron-order acrylate microgel can be prepared by adopting a dispersion polymerization method; the addition of a small amount of microgel to the coating can improve sag resistance. The emulsion polymerization process for preparing reactive microgel is mature, but can be applied to coating after centrifugal filtration, spray drying or freeze drying. The hydroxyl acrylic emulsion with the microgel core structure synthesized by the method is used for bi-component waterborne polyurethane, and the sagging resistance of the coating in vertical surface coating can be improved. The high-concentration acrylate microgel can be synthesized by adopting a microemulsion method, and can be used for modifying high-solid hydroxyl acrylic resin to improve the pseudoplasticity of the coating. The reactive microgel is capable of forming heterogeneous coating films with good mechanical properties. For example, microgel particles obtained by soap-free emulsion polymerization of styrene and carboxyl-terminated unsaturated polyester as monomers are used for modifying unsaturated polyester, so that the impact strength of the unsaturated polyester can be greatly improved.
The microgel has a plurality of active groups in the interior or on the surface, is easy to further react with other monomers, and has a cross-linked structure in the interior, so that the curing speed of a coating film is accelerated. For example, a core/shell type reactive microgel is synthesized from an acrylate monomer, and a functional group remaining in the shell layer is subjected to a crosslinking reaction with an amino resin. The curing agent can generate a cross-linked network only by cross-linking with the shell layer, thereby accelerating the curing.
CN1624009A discloses a preparation method of a hydroxy acrylic emulsion with a microgel core structure, which comprises the steps of taking a vinyl silane coupling agent as a cross-linking agent, copolymerizing the vinyl silane coupling agent and an acrylate monomer to obtain a core with the microgel structure, and then copolymerizing a hydroxy vinyl monomer and an acrylate monomer on the surface of the core to form a shell rich in hydroxy groups to obtain the hydroxy acrylic emulsion with the microgel core structure; the emulsion has a core-shell structure, wherein the core part is hydrophobic siloxane, the shell part contains hydroxyl with strong hydrophilicity, and the shell layer can play a shielding role in the condensation reaction of the siloxane among particles. The emulsion needs to use a vinyl silane coupling agent and needs to form a core-shell structure, so that the production cost is obviously increased.
CN105837757A discloses a microgel aqueous acrylic acid shell-core resin emulsion, which is obtained by reacting 13-16 parts of acrylic acid resin aqueous dispersion, 18-21 parts of vinyl monomer, 20.5-27.6 parts of acrylic acid and ester monomer, 0.3-0.6 part of initiator, 5-6 parts of organic solvent and 49-53 parts of water. The above patent documents do not disclose that the use of a hydroxyl group-containing acrylate in combination with a polyol polyacrylate improves the sag resistance of a paint film, nor how an aqueous acrylic resin dispersion is prepared, nor does it demonstrate that the addition of such an emulsion to an aqueous coating can improve the sag resistance of a paint film.
Disclosure of Invention
In view of the above, the present invention provides an acrylate microgel emulsion, which has a low production cost and can significantly improve sag resistance of a paint film.
The invention also aims to provide a preparation method of the acrylic ester microgel emulsion, which has simple process and reliable product performance.
It is a further object of the present invention to provide the use of the above acrylate microgel emulsions, which can significantly improve the sag resistance of the paint film.
In one aspect, the present invention provides an acrylate microgel emulsion prepared from a first raw material comprising:
wherein the emulsifier is polymerized from a second raw material comprising alkyl (meth) acrylate, (meth) acrylic acid, acrylamide, and hydroxyalkyl (meth) acrylate.
According to the acrylate microgel emulsion of the present invention, preferably, in the first raw material and the second raw material, the alkyl (meth) acrylate is selected from one or more of methyl methacrylate, ethyl acrylate and butyl acrylate.
According to the acrylate microgel emulsion of the present invention, preferably, in the first raw material, the vinyl aromatic compound is selected from one or more of styrene, alpha-methyl styrene, and 3-tert-butyl styrene.
According to the acrylate microgel emulsion of the present invention, preferably, in the first raw material and the second raw material, the hydroxyalkyl (meth) acrylate is selected from one or more of hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate.
According to the acrylate microgel emulsion of the invention, preferably, in the first raw material, the unsaturated monomer containing two ethylenic bonds is a dibasic ester formed by reacting a dihydric alcohol with (meth) acrylic acid or a dibasic ester formed by reacting a dihydric alcohol with an alkyl (meth) acrylate.
According to the acrylate microgel emulsion of the present invention, preferably, the initiator is selected from persulfate, azobisisoheptonitrile or azobisisobutyronitrile.
According to the acrylate microgel emulsion, preferably, in the first raw material, the unsaturated monomer containing two ethylenic bonds is ethylene glycol dimethacrylate, and the vinyl aromatic compound is styrene; in the first raw material and the second raw material, the alkyl (meth) acrylate is a mixture of methyl methacrylate and butyl acrylate, and the hydroxyalkyl (meth) acrylate is hydroxyethyl (meth) acrylate; the initiator is azobisisobutyronitrile.
In another aspect, the present invention provides a method for preparing the acrylate microgel emulsion, comprising the following steps:
mixing part of water, part of an emulsifier, alkyl (meth) acrylate, vinyl aromatic compound, hydroxyalkyl (meth) acrylate and unsaturated monomer containing two ethylenic bonds to form a pre-emulsion;
mixing an initiator with an organic solvent to form an initiator solution;
mixing the residual water and the residual emulsifier to form a mixed solution, and heating to 70-80 ℃; then, simultaneously dripping the pre-emulsion and the initiator solution into the mixed solution, finishing dripping within 2-5 hours, reacting at 70-80 ℃ for 0.5-5 hours, and cooling to room temperature to obtain acrylate microgel emulsion;
wherein the weight ratio of part of water to the rest of water is 1-1.5: 1, and the weight ratio of the part of emulsifier to the rest of emulsifier is 0.8-1.5: 1.
According to the preparation method of the present invention, preferably, the preparation method further comprises the steps of:
mixing water, dihydric alcohol and dihydric alcohol monoalkyl ether to form a dispersion liquid, heating to 70-80 ℃, dripping a mixture containing (methyl) acrylic acid alkyl ester, (methyl) acrylic acid, acrylamide and (methyl) acrylic acid hydroxyalkyl ester into the dispersion liquid within 2-5 hours, reacting for 1-3 hours at 70-80 ℃, cooling to 50-65 ℃, and adjusting the pH value to 7-8 to obtain the emulsifier.
In another aspect, the invention provides a use of the acrylate microgel emulsion for improving sag resistance of a coating, wherein the acrylate microgel emulsion is used in an amount of 3-25 wt% based on the total weight of the coating.
The invention adopts the reagents frequently used in the coating field as raw materials to synthesize the acrylic emulsion with the microgel structure, thereby having lower production cost. The invention combines the hydroxyalkyl (meth) acrylate, the unsaturated monomer containing two ethylenic bonds and the reactive emulsifier, thereby effectively improving the sag resistance of the paint film. In a preferred embodiment of the present invention, the amount of the microgel in the coating is controlled so that the sag resistance of the paint film is significantly improved.
Drawings
FIG. 1 is a photograph of a paint film of Experimental example 3.
Detailed Description
The present invention will be further described with reference to the following specific examples, but the scope of the present invention is not limited thereto.
The acrylate microgel emulsion of the present invention means a microgel emulsion prepared from a raw material containing an acrylate monomer. Microgels are crosslinked polymer particles dispersed in a medium comprising water to form a microgel emulsion.
In the present invention, "(meth) acrylic acid … …" is an acronym that has its ordinary meaning in the art, meaning "acrylic acid … …" or "methacrylic acid … …".
< acrylic acid ester microgel emulsion >
The acrylate microgel emulsion of the present invention is prepared from a first raw material comprising water, an alkyl (meth) acrylate, a vinyl aromatic compound, a hydroxyalkyl (meth) acrylate, an unsaturated monomer containing two ethylenic bonds, an initiator, and an emulsifier. The first feedstock may also contain other components, such as small amounts of dispersants. Preferably, the first raw material consists of only water, alkyl (meth) acrylate, vinyl aromatic compound, hydroxyalkyl (meth) acrylate, unsaturated monomer containing two ethylenic bonds, initiator, and emulsifier. The following are described one by one.
In the present invention, the kind of water is not particularly limited, and for example, deionized water, distilled water, etc. The amount of water is 200 to 300 parts by weight, preferably 210 to 280 parts by weight, and more preferably 210 to 230 parts by weight.
The alkyl (meth) acrylate in the first raw material is a product obtained by reacting a monohydric alkyl alcohol with (meth) acrylic acid (or ester). The alkyl group may be a C1-C8 alkyl group, preferably a C1-C6 alkyl group, more preferably a C1-C4 alkyl group. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and the like. The alkyl (meth) acrylate may be a C1-C8 alkyl (meth) acrylate, preferably a C1-C6 alkyl (meth) acrylate, more preferably a C1-C4 alkyl (meth) acrylate; specific examples include, but are not limited to, methyl methacrylate, ethyl acrylate, or butyl acrylate. The alkyl (meth) acrylate of the present invention may be selected from one or more of methyl methacrylate, ethyl acrylate, butyl acrylate. In one embodiment of the present invention, the alkyl (meth) acrylate is selected from a mixture of methyl methacrylate and butyl acrylate. The weight ratio of the two components can be 50-85: 10-25, preferably 60-70: 15-20. This improves the sag resistance of the acrylate microgel emulsion when used in coatings. The amount of the alkyl (meth) acrylate is 70 to 100 parts by weight, preferably 75 to 90 parts by weight, and more preferably 80 to 85 parts by weight.
The vinyl aromatic compound in the first raw material represents an aromatic compound having a vinyl group. The vinyl aromatic compound may be a vinyl-substituted benzene, alkylbenzene, naphthalene, alkylnaphthalene, biphenyl, or the like. The vinyl aromatic compound may be selected from one or more of styrene, alpha-methylstyrene, 3-tert-butylstyrene. According to one embodiment of the invention, the vinyl aromatic compound is styrene. The amount of the vinyl aromatic compound is 8 to 15 parts by weight, preferably 9 to 13 parts by weight, and more preferably 10 to 12 parts by weight. Thus, better sag resistance can be obtained.
The hydroxyalkyl (meth) acrylate in the first raw material represents an alkyl (meth) acrylate having a hydroxyl group, and is generally obtained by reacting one hydroxyl group of a diol with (meth) acrylic acid (or ester). The alkyl group in the hydroxyalkyl ester may be a C2-C6 alkyl group, preferably a C2-C5 alkyl group, and more preferably a C2-C3 alkyl group. Examples of hydroxyalkyl groups include, but are not limited to, hydroxyethyl, hydroxypropyl, hydroxybutyl, and the like. The hydroxyalkyl (meth) acrylate may be selected from one or more of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate; preferably hydroxyethyl (meth) acrylate. This improves the sag resistance of the acrylate microgel emulsion when used in coatings. The hydroxyalkyl (meth) acrylate may be used in an amount of 8 to 15 parts by weight, preferably 9 to 13 parts by weight, and more preferably 10 to 12 parts by weight. Thus, better sag resistance can be obtained.
The unsaturated monomer containing two ethylenic bonds in the first raw material may be a dibasic ester formed by reacting a dihydric alcohol with (meth) acrylic acid, or a dibasic ester formed by reacting a dihydric alcohol with an alkyl (meth) acrylate. Examples of glycols include, but are not limited to, ethylene glycol, propylene glycol, butylene glycol, and the like, with ethylene glycol being preferred. (meth) acrylic acid or alkyl esters thereof include, but are not limited to, acrylic acid, alkyl acrylates, methacrylic acid, alkyl methacrylates. The alkyl group may be a C1-C8 alkyl group, preferably a C1-C6 alkyl group, more preferably a C1-C4 alkyl group. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and the like. According to one embodiment of the invention, the unsaturated monomer containing two ethylenic bonds is ethylene glycol dimethacrylate. This improves the sag resistance of the acrylate microgel emulsion when used in coatings. The amount of the unsaturated monomer having two ethylenic bonds may be 6 to 12 parts by weight, preferably 7 to 11 parts by weight, and more preferably 8 to 10 parts by weight. Thus, better sag resistance can be obtained.
The initiator in the first starting material is an initiator that can initiate free radical polymerization. The initiator may be selected from persulfates, azobisisoheptonitrile, or azobisisobutyronitrile. Examples of persulfates include, but are not limited to, ammonium persulfate, potassium persulfate. The initiator is preferably ammonium persulfate or azobisisobutyronitrile; more preferably azobisisobutyronitrile. The amount of the initiator may be 1 to 5 parts by weight, preferably 2 to 3 parts by weight.
According to an embodiment of the present invention, in the first raw material, the unsaturated monomer containing two ethylenic bonds is ethylene glycol dimethacrylate, and the hydroxyalkyl (meth) acrylate is hydroxyethyl (meth) acrylate; the alkyl (methyl) acrylate is a mixture of methyl methacrylate and butyl acrylate, the vinyl aromatic compound is styrene, and the initiator is azobisisobutyronitrile. This may further improve the sag resistance of the acrylate microgel emulsion when used in coatings.
The emulsifier in the first feedstock is polymerized from a second feedstock comprising an alkyl (meth) acrylate, a (meth) acrylic acid, an acrylamide, and a hydroxyalkyl (meth) acrylate. This makes it possible to obtain emulsifiers having a certain reactivity. The emulsifier may be used in an amount of 15 to 38 parts by weight, preferably 20 to 35 parts by weight, and more preferably 25 to 31 parts by weight. The anti-sagging performance of the acrylate microgel emulsion when used in a coating can be improved by adopting the emulsifier with the dosage. The second raw material will be described in detail below.
The alkyl (meth) acrylate in the second raw material is a product obtained by reacting a monohydric alkyl alcohol with (meth) acrylic acid (or ester). The alkyl group may be a C1-C8 alkyl group, preferably a C1-C6 alkyl group, more preferably a C1-C4 alkyl group. Examples of alkyl groups include, but are not limited to, methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, and the like. The alkyl (meth) acrylate may be a C1-C8 alkyl (meth) acrylate, preferably a C1-C6 alkyl (meth) acrylate, more preferably a C1-C4 alkyl (meth) acrylate; specific examples include, but are not limited to, methyl methacrylate, ethyl acrylate, or butyl acrylate. The alkyl (meth) acrylate of the present invention may be selected from one or more of methyl methacrylate, ethyl acrylate, butyl acrylate. In one embodiment of the present invention, the alkyl (meth) acrylate is a mixture of methyl methacrylate and butyl acrylate. The weight ratio of methyl methacrylate to butyl acrylate may be 200-300: 200-250, preferably 220-260: 200-250. The amount of the alkyl (meth) acrylate is 350 to 600 parts by weight, preferably 380 to 550 parts by weight, and more preferably 390 to 500 parts by weight.
The (meth) acrylic acid in the second raw material represents acrylic acid or methacrylic acid. The amount of (meth) acrylic acid is 50 to 90 parts by weight, preferably 55 to 85 parts by weight, and more preferably 65 to 80 parts by weight.
The amount of the acrylamide in the second raw material is 4 to 15 parts by weight, preferably 5 to 13 parts by weight, and more preferably 6 to 10 parts by weight.
The hydroxyalkyl (meth) acrylate in the second raw material represents an alkyl (meth) acrylate having a hydroxyl group, and is generally obtained by reacting one hydroxyl group of a diol with (meth) acrylic acid (or ester). The alkyl group in the hydroxyalkyl ester may be a C2-C6 alkyl group, preferably a C2-C5 alkyl group, and more preferably a C2-C3 alkyl group. Examples of hydroxyalkyl groups include, but are not limited to, hydroxyethyl, hydroxypropyl, hydroxybutyl, and the like. The hydroxyalkyl (meth) acrylate may be selected from one or more of hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate; preferably hydroxyethyl (meth) acrylate. This improves the emulsifier properties and results in a stable emulsion. The hydroxyalkyl (meth) acrylate may be used in an amount of 100 to 250 parts by weight, preferably 130 to 200 parts by weight, and more preferably 150 to 195 parts by weight. Thus, better sag resistance can be obtained.
The second feedstock may also include water, glycol monoalkyl ether, and an initiator. The type of water is not particularly limited, and may be deionized water, distilled water, or the like. The amount of water may be 200 to 600 parts by weight, preferably 220 to 500 parts by weight. Examples of glycols include ethylene glycol, propylene glycol, and the like. The amount of the glycol may be 300 to 900 parts by weight, preferably 380 to 600 parts by weight. The glycol monoalkyl ether can be glycol monobutyl ether. The amount of the glycol monoalkyl ether may be 30 to 90 parts by weight, preferably 38 to 60 parts by weight. The initiator is an initiator which can initiate radical polymerization. The initiator may be selected from persulfates, azobisisoheptonitrile, or azobisisobutyronitrile. Examples of persulfates include, but are not limited to, ammonium persulfate, potassium persulfate. The initiator is preferably ammonium persulfate or azobisisobutyronitrile; more preferably azobisisobutyronitrile. The amount of the initiator may be 8 to 30 parts by weight, preferably 10 to 25 parts by weight.
< preparation method and use >
The preparation method of the acrylate microgel emulsion comprises a pre-emulsion preparation step, an initiator solution preparation step, a polymerization step and the like. The order of the pre-emulsion preparation step and the initiator solution preparation step is not particularly limited.
In the pre-emulsion preparation step, part of water, part of an emulsifier, alkyl (meth) acrylate, vinyl aromatic compound, hydroxyalkyl (meth) acrylate, and unsaturated monomer containing two ethylenic bonds are mixed to form a pre-emulsion. The types and the amounts of the components are as described above. By forming a pre-emulsion, it is advantageous to obtain a stable acrylate microgel emulsion.
In the initiator solution preparing step, an initiator is mixed with an organic solvent to form an initiator solution. The initiator is an initiator which can initiate radical polymerization. The initiator may be selected from persulfates, azobisisoheptonitrile, or azobisisobutyronitrile. Examples of persulfates include, but are not limited to, ammonium persulfate, potassium persulfate. The initiator is preferably ammonium persulfate or azobisisobutyronitrile; more preferably azobisisobutyronitrile. The amount of the initiator may be 1 to 5 parts by weight, preferably 2 to 3 parts by weight. The organic solvent can be any organic solvent which can dissolve the initiator and has certain compatibility with water. The invention finds that N-methyl pyrrolidone is particularly suitable for obtaining stable acrylate microgel emulsion. The amount of the organic solvent may be 15 to 35 parts by weight, preferably 20 to 30 parts by weight.
In the polymerization step, mixing the residual water and the residual emulsifier to form a mixed solution, and heating to 70-80 ℃; and then simultaneously dripping the pre-emulsion and the initiator solution into the mixed solution, finishing dripping within 2-5 hours, reacting for 0.5-5 hours at 70-80 ℃, and cooling to room temperature to obtain the acrylate microgel emulsion. The weight ratio of the partial water to the residual water is 1-1.5: 1, preferably 1-1.2: 1. The weight ratio of the partial emulsifier to the rest emulsifier is 0.8-1.5: 1, preferably 0.9-1.3: 1. And heating the mixed solution to 70-80 ℃, preferably 70-75 ℃, and then simultaneously dropwise adding the pre-emulsion and the initiator solution. The solution is slowly dripped, and the dripping is completed within 2 to 5 hours, preferably 2 to 3 hours. This facilitates the formation of stable acrylate microgel emulsions, thereby improving sag resistance. Reacting at 70-80 ℃, preferably 70-75 ℃ for 0.5-5 hours, preferably 1-3 hours, and cooling to room temperature to obtain the acrylate microgel emulsion. The emulsion obtained can be used directly for coating modification.
The preparation method of the invention can also comprise the preparation steps of the emulsifier: mixing water, dihydric alcohol and dihydric alcohol monoalkyl ether to form a dispersion, heating to 70-80 ℃, preferably 70-75 ℃, dripping a mixture containing (methyl) acrylic acid alkyl ester, (methyl) acrylic acid, acrylamide and (methyl) acrylic acid hydroxyalkyl ester into the dispersion within 2-5 hours, preferably 2-3 hours, reacting for 1-3 hours, preferably 1-2 hours at 70-80 ℃, preferably 70-75 ℃, cooling to 50-65 ℃, preferably 55-60 ℃, and adjusting the pH value to 7-8, thereby obtaining the emulsifier. The pH regulator may be N, N-dimethylethanolamine. The kinds and amounts of the alkyl (meth) acrylate, the (meth) acrylic acid, the acrylamide and the hydroxyalkyl (meth) acrylate are as described above.
In the above mixture, water, glycol monoalkyl ether and an initiator may also be contained. The type of water is not particularly limited, and may be deionized water, distilled water, or the like. The amount of water may be 200 to 600 parts by weight, preferably 220 to 500 parts by weight. Examples of glycols include ethylene glycol, propylene glycol, and the like. The amount of the glycol may be 300 to 900 parts by weight, preferably 380 to 600 parts by weight. The glycol monoalkyl ether can be glycol monobutyl ether. The amount of the glycol monoalkyl ether may be 30 to 90 parts by weight, preferably 38 to 60 parts by weight. The initiator is an initiator which can initiate radical polymerization. The initiator may be selected from persulfates, azobisisoheptonitrile, or azobisisobutyronitrile. Examples of persulfates include, but are not limited to, ammonium persulfate, potassium persulfate. The initiator is preferably ammonium persulfate or azobisisobutyronitrile; more preferably azobisisobutyronitrile. The amount of the initiator may be 8 to 30 parts by weight, preferably 10 to 25 parts by weight.
According to one embodiment of the invention, part of water, part of dihydric alcohol and part of dihydric alcohol monoalkyl ether are mixed to form a dispersion, the temperature is raised to 70-80 ℃, preferably 70-75 ℃, a mixture containing (methyl) acrylic acid alkyl ester, (methyl) acrylic acid, acrylamide, (methyl) acrylic acid hydroxyalkyl ester, part of water, part of dihydric alcohol monoalkyl ether and an initiator is dripped into the dispersion within 2-5 hours, preferably 2-3 hours, the reaction is carried out for 1-3 hours, preferably 1-2 hours at 70-80 ℃, preferably 70-75 ℃, the temperature is lowered to 50-65 ℃, preferably 55-60 ℃, and the pH value is adjusted to 7-8, so as to obtain the emulsifier. The weight ratio of the part of water to the rest of water is 1-8: 1, preferably 2-5: 1. The weight ratio of part of dihydric alcohol to the rest of dihydric alcohol is 2-6: 1, preferably 2-5: 1. The weight ratio of part of glycol monoalkyl ether to the rest of glycol monoalkyl ether is 3-10: 1, preferably 5-8: 1.
The acrylic ester microgel emulsion obtained by the method can be directly mixed with paint to improve the sagging resistance of the paint. The invention also provides the application of the acrylate microgel emulsion in improving the sagging resistance of the coating, wherein the acrylate microgel emulsion is used in an amount of 3-28 wt%, preferably 6-25 wt%, and more preferably 13-20 wt%, based on the total weight of the coating. Compared with the coating without the acrylate microgel emulsion, the anti-sagging performance of the coating can be obviously improved by adding the acrylate microgel emulsion. However, the amount of acrylate microgel emulsion used is not simply a linear increase in sag resistance of the coating. When the dosage of the microgel emulsion reaches more than 4 wt%, the maximum wet film thickness of a paint film formed by the paint without sagging is increased by more than three times. When the dosage of the microgel emulsion reaches more than 20 wt%, the maximum wet film thickness of a paint film without sagging is increased by more than five times; continuing to increase the amount of microgel emulsion too much results in a decrease in the maximum wet film thickness at which the paint film does not sag.
The test methods and materials of the present invention are described below.
And (3) measuring the anti-sagging performance: GB/T9264-2012 (determination of the sag resistance of the paint) is adopted, the temperature is 23 +/-2 ℃, and the relative humidity is 50 +/-5%.
Epoxy resin primer: baojun emerging building materials (Tianjin) Co., Ltd., WEP-099.
Preparation example 1
Water, ethylene glycol butyl ether, methyl methacrylate, hydroxyethyl methacrylate, acrylic acid, butyl acrylate, acrylamide, and azobisisobutyronitrile were mixed to form a mixed solution according to the formulation of table 1.
According to the formulation of table 1, water, ethylene glycol and butyl cellosolve were added to a reaction kettle, mixed to form a dispersion, and heated to 80 ℃. And dropwise adding the mixed solution into a reaction kettle for 2h, reacting for 1h at 80 ℃, cooling to 60 ℃, adding N, N-dimethylethanolamine to adjust the pH value to 7, and obtaining the emulsifier.
Preparation example 2
Water, ethylene glycol butyl ether, methyl methacrylate, hydroxyethyl methacrylate, acrylic acid, butyl acrylate, acrylamide, and azobisisobutyronitrile were mixed to form a mixed solution according to the formulation of table 1.
According to the formulation of table 1, water, ethylene glycol and butyl cellosolve were added to a reaction kettle, mixed to form a dispersion, and heated to 80 ℃. And dropwise adding the mixed solution into a reaction kettle for 3h, reacting for 1h at 80 ℃, cooling to 60 ℃, adding N, N-dimethylethanolamine to adjust the pH value to 8, and obtaining the emulsifier.
TABLE 1
Example 1
100g of water, 15g of emulsifier (preparation 1), 65g of methyl methacrylate, 10g of styrene, 15g of n-butyl acrylate, 10g of hydroxyethyl methacrylate and 10g of ethylene glycol dimethacrylate were mixed to form a pre-emulsion according to the formulation of Table 2.
2.5g of azobisisobutyronitrile and 20g of N-methylpyrrolidone were mixed to form an initiator solution.
110g of water and 15g of emulsifier (preparation example 1) were added to the reaction vessel, and the temperature was raised to 70 ℃ with stirring. Then, the pre-emulsion and the initiator solution are simultaneously dripped into a reaction kettle, the dripping is completed within 2 hours, the reaction is carried out for 2 hours at 70 ℃, and the reaction temperature is reduced to room temperature, so as to obtain the acrylic ester microgel emulsion (the solid content is 30 wt%).
Example 2
100g of water, 15g of emulsifier (preparation 1), 60g of methyl methacrylate, 10g of styrene, 20g of n-butyl acrylate, 11g of hydroxyethyl methacrylate and 9g of ethylene glycol dimethacrylate were mixed to form a pre-emulsion according to the formulation of Table 2.
2.5g of azobisisobutyronitrile and 20g of N-methylpyrrolidone were mixed to form an initiator solution.
110g of water and 16g of emulsifier (preparation example 1) were added to the reaction vessel, and the temperature was raised to 70 ℃ with stirring. Then, the pre-emulsion and the initiator solution are simultaneously dripped into a reaction kettle, the dripping is completed within 2 hours, the reaction is carried out for 2 hours at 70 ℃, and the reaction temperature is reduced to room temperature, so as to obtain the acrylic ester microgel emulsion (the solid content is 30 wt%).
Example 3
100g of water, 15g of emulsifier (preparation 1), 65g of methyl methacrylate, 10g of styrene, 15g of n-butyl acrylate, 10g of hydroxyethyl methacrylate and 10g of ethylene glycol dimethacrylate were mixed to form a pre-emulsion according to the formulation of Table 2.
2.5g of azobisisobutyronitrile and 20g of N-methylpyrrolidone were mixed to form an initiator solution.
110g of water and 15g of emulsifier (preparation example 1) were added to the reaction vessel, and the temperature was raised to 80 ℃ with stirring. Then, the pre-emulsion and the initiator solution are simultaneously dripped into a reaction kettle, the dripping is completed within 3 hours, the reaction is carried out for 1 hour at the temperature of 80 ℃, and the reaction temperature is reduced to room temperature, so as to obtain the acrylic ester microgel emulsion (the solid content is 30 wt%).
Example 4
100g of water, 15g of emulsifier (preparation 1), 60g of methyl methacrylate, 10g of styrene, 20g of n-butyl acrylate, 11g of hydroxyethyl methacrylate and 9g of ethylene glycol dimethacrylate were mixed to form a pre-emulsion according to the formulation of Table 2.
2.5g of azobisisobutyronitrile and 20g of N-methylpyrrolidone were mixed to form an initiator solution.
110g of water and 16g of emulsifier (preparation example 1) were added to the reaction vessel, and the temperature was raised to 80 ℃ with stirring. Then, the pre-emulsion and the initiator solution are simultaneously dripped into a reaction kettle, the dripping is completed within 3 hours, the reaction is carried out for 1 hour at the temperature of 80 ℃, and the reaction temperature is reduced to room temperature, so as to obtain the acrylic ester microgel emulsion (the solid content is 30 wt%).
Example 5
100g of water, 15g of emulsifier (preparation 1), 65g of methyl methacrylate, 10g of styrene, 15g of n-butyl acrylate, 10g of hydroxyethyl methacrylate and 10g of ethylene glycol dimethacrylate were mixed to form a pre-emulsion according to the formulation of Table 2.
2.5g of azobisisobutyronitrile and 20g of N-methylpyrrolidone were mixed to form an initiator solution.
110g of water and 15g of emulsifier (preparation example 1) were added to the reaction vessel, and the temperature was raised to 80 ℃ with stirring. Then, the pre-emulsion and the initiator solution are simultaneously dripped into a reaction kettle, the dripping is completed within 2 hours, the reaction is carried out for 1.5 hours at the temperature of 80 ℃, and the temperature is reduced to room temperature, so as to obtain the acrylic ester microgel emulsion (the solid content is 30 wt%).
Example 6
100g of water, 15g of emulsifier (preparation 1), 60g of methyl methacrylate, 10g of styrene, 20g of n-butyl acrylate, 11g of hydroxyethyl methacrylate and 9g of ethylene glycol dimethacrylate were mixed to form a pre-emulsion according to the formulation of Table 2.
2.5g of azobisisobutyronitrile and 20g of N-methylpyrrolidone were mixed to form an initiator solution.
110g of water and 16g of emulsifier (preparation example 1) were added to the reaction vessel, and the temperature was raised to 80 ℃ with stirring. Then, the pre-emulsion and the initiator solution are simultaneously dripped into a reaction kettle, the dripping is completed within 2 hours, the reaction is carried out for 1.5 hours at the temperature of 80 ℃, and the temperature is reduced to room temperature, so as to obtain the acrylic ester microgel emulsion (the solid content is 30 wt%).
TABLE 2
Examples 1 to 6
The acrylate microgel emulsion of example 1 was mixed with an epoxy primer and the viscosity was adjusted to 25s (coat 4# cup viscosity determination). The test was carried out using GB/T9264-2012 (determination of the sag resistance of paints) and the results are given in the following table. A photograph of the paint film is shown in FIG. 1.
TABLE 3
The preparation process of example 1 was repeated 3 times to obtain three batches of enoate microgel emulsions, and sag resistance tests were performed under the conditions of the experimental examples described above, with results consistent with table 3.
It can be seen from the table that the addition of the acrylate microgel emulsion of the present invention can significantly improve the sag resistance of the primer compared to the epoxy resin primer without the addition of the acrylate microgel emulsion of the present invention. When the dosage of the microgel emulsion reaches more than 4 wt%, the maximum wet film thickness of a paint film without sagging is increased by more than three times. When the dosage of the microgel emulsion reaches more than 20 wt%, the maximum wet film thickness of a paint film without sagging is increased by more than five times; continuing to increase the amount of microgel emulsion too much results in a decrease in the maximum wet film thickness at which the paint film does not sag.
The present invention is not limited to the above-described embodiments, and any variations, modifications, and substitutions which may occur to those skilled in the art may be made without departing from the spirit of the invention.
Claims (9)
1. The application of the acrylate microgel emulsion in improving the sagging resistance of the coating is characterized in that the dosage of the acrylate microgel emulsion is 13-20 wt% based on the total weight of the coating; the coating is epoxy resin primer;
the acrylate microgel emulsion is prepared from a first raw material comprising the following components:
wherein the emulsifier is obtained by polymerizing a second raw material comprising 350-600 parts by weight of alkyl (meth) acrylate, 50-90 parts by weight of (meth) acrylic acid, 4-15 parts by weight of acrylamide and 100-250 parts by weight of hydroxyalkyl (meth) acrylate.
2. Use according to claim 1, characterized in that in the first and second starting materials the alkyl (meth) acrylate is selected from one or more of methyl methacrylate, ethyl acrylate, butyl acrylate.
3. Use according to claim 2, characterized in that in the first feedstock the vinyl aromatic compound is selected from one or more of styrene, α -methylstyrene, 3-tert-butylstyrene.
4. Use according to claim 3, wherein the hydroxyalkyl (meth) acrylate is selected from one or more of hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate in the first and second starting materials.
5. Use according to claim 4, wherein in the first starting material the said two ethylenically unsaturated monomers are dibasic esters formed by reacting a diol with (meth) acrylic acid or dibasic esters formed by reacting a diol with alkyl (meth) acrylates.
6. Use according to claim 5, characterized in that the initiator is selected from persulfates, azobisisoheptonitrile or azobisisobutyronitrile.
7. Use according to claim 6, characterized in that:
in the first raw material, the unsaturated monomer containing two ethylenic bonds is ethylene glycol dimethacrylate, and the vinyl aromatic compound is styrene;
in the first raw material and the second raw material, the alkyl (meth) acrylate is a mixture of methyl methacrylate and butyl acrylate, and the hydroxyalkyl (meth) acrylate is hydroxyethyl (meth) acrylate; and
the initiator is azobisisobutyronitrile.
8. The use according to any one of claims 1 to 7, wherein the preparation method of the acrylate microgel emulsion comprises the following steps:
mixing part of water, part of an emulsifier, alkyl (meth) acrylate, vinyl aromatic compound, hydroxyalkyl (meth) acrylate and unsaturated monomer containing two ethylenic bonds to form a pre-emulsion;
mixing an initiator with an organic solvent to form an initiator solution;
mixing the residual water and the residual emulsifier to form a mixed solution, and heating to 70-80 ℃; then, simultaneously dripping the pre-emulsion and the initiator solution into the mixed solution, finishing dripping within 2-5 hours, reacting at 70-80 ℃ for 0.5-5 hours, and cooling to room temperature to obtain acrylate microgel emulsion;
wherein the weight ratio of part of water to the rest of water is 1-1.5: 1, and the weight ratio of the part of emulsifier to the rest of emulsifier is 0.8-1.5: 1.
9. Use according to claim 8, characterized in that it further comprises the step of preparing an emulsifier:
mixing water, dihydric alcohol and dihydric alcohol monoalkyl ether to form a dispersion liquid, heating to 70-80 ℃, dripping a mixture containing (methyl) acrylic acid alkyl ester, (methyl) acrylic acid, acrylamide and (methyl) acrylic acid hydroxyalkyl ester into the dispersion liquid within 2-5 hours, reacting for 1-3 hours at 70-80 ℃, cooling to 50-65 ℃, and adjusting the pH value to 7-8 to obtain the emulsifier.
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