Styrene-acrylic emulsion, preparation method thereof and latex powder using styrene-acrylic emulsion

Abstract

The invention discloses a styrene-acrylic emulsion, a preparation method thereof and latex powder applying the styrene-acrylic emulsion. The invention provides a styrene-acrylic emulsion which comprises the following raw materials in parts by weight: 20-100 parts of styrene, 20-100 parts of acrylate, 0.5-2 parts of a reactive emulsifier, 5-15 parts of polyvinyl alcohol, 0-5 parts of a functional monomer, 0-5 parts of a crosslinking monomer and 0.3-1.2 parts of an initiator, the molecular structure of the reactive emulsifier comprises an aromatic group and a carbon-carbon double bond structure. A carbon-carbon double bond structure in the selected reactive emulsifier can participate in an emulsion polymerization reaction, and a carbon-carbon double bond is grafted on a polymer molecular chain in a chemical bond manner, so that on one hand, a hydrophobic aromatic group is introduced into the molecular chain of an emulsion polymer to promote the entry of free styrene, and on the other hand, a hydrophobic aromatic group is introduced into the molecular chain of the emulsion polymer; the length of a latex molecular chain segment in the emulsion can be kept relatively uniform, and the particle size and the particle size distribution condition of the emulsion can be regulated and controlled more finely; on the other hand, the cohesion strength of a polymer molecular chain can be improved, the emulsion film is more compact through the action, and the water resistance of a paint film is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of styrene-acrylic emulsions, and in particular relates to a styrene-acrylic emulsion and a preparation method thereof, and a redispersible latex powder using the same. Background Art

[0002] Redispersible latex powder is a free-flowing powder obtained by drying and pulverizing a polymer emulsion. Its characteristic is that it can quickly recover after contacting water to form a stable dispersion with performance close to that of the original emulsion. At present, the redispersible latex powder on the market is mainly based on vinyl acetate or ethylene-vinyl acetate copolymer (VAE) emulsion polymer systems. However, the ester groups in the molecular chain structure of these polymers have strong hydrophilicity, resulting in poor water resistance in building materials applications. In order to solve this problem, researchers have developed a styrene / acrylate polymer system (styrene-acrylic polymer for short). The benzene ring in the styrene-acrylic polymer structure gives the emulsion polymer good hydrophobic properties, thereby improving the water resistance of the latex powder.

[0003] For latex powder prepared using styrene acrylic emulsion, in the prior art, polyvinyl alcohol protective colloid is usually added during the preparation of styrene acrylic emulsion to give the latex powder made using the styrene acrylic emulsion redispersibility. However, the introduction of polyvinyl alcohol often leads to poor hydrophobicity of the paint film formed by the styrene acrylic emulsion.

[0004] Therefore, it is necessary to develop a styrene acrylic emulsion with excellent hydrophobic properties to address the above defects. Summary of the invention

[0005] The invention provides a styrene-acrylic emulsion, a preparation method thereof and latex powder using the same. The paint film formed by the styrene-acrylic emulsion has good hydrophobicity, and the latex powder using the same can have better water resistance and weather resistance while maintaining good mechanical properties.

[0006] According to one aspect of the present invention, a styrene-acrylic emulsion is provided, wherein the raw materials thereof include the following materials, calculated by weight: 20 to 100 parts of styrene, 20 to 100 parts of acrylate, 0.5 to 2 parts of reactive emulsifier, 5 to 15 parts of polyvinyl alcohol, 0 to 5 parts of functional monomer, 0 to 5 parts of cross-linking monomer, and 0.3 to 1.2 parts of initiator; the molecular structure of the reactive emulsifier includes an aromatic group and a carbon-carbon double bond structure.

[0007] The carbon-carbon double bond structure in the reactive emulsifier selected by the present invention can participate in the emulsion polymerization reaction, and the carbon-carbon double bond is grafted on the polymer molecular chain in the form of a chemical bond, thereby using the reactive emulsifier to introduce aromatic groups on the molecular chain of the emulsion polymer. Based on the fact that the raw materials for synthesizing styrene-acrylic emulsion contain a large amount of styrene, the aromatic groups of the reactive emulsifier provide a convenient channel for monomers such as styrene to enter the latex, which promotes the effective aggregation and reaction of monomers such as styrene in the emulsion polymerization system, helps to keep the length of the latex molecular chain segments in the emulsion relatively uniform, and is conducive to more finely regulating the particle size and particle size distribution of the emulsion. In addition, as mentioned above, the reactive emulsifier can improve the cohesive strength of the polymer molecular chain by participating in the polymerization reaction and grafting on the polymer molecular chain in the form of a chemical bond, thereby promoting the emulsion film to be more dense and improving the water resistance of the paint film, thereby helping to make the paint film formed by the emulsion better resist the influence of the external environment and maintain good mechanical properties under high humidity and high heat conditions.

[0008] Preferably, the weight ratio of styrene to acrylate is (40-50):(45.8-55).

[0009] Preferably, the weight ratio of the reactive emulsifier to the polyvinyl alcohol is 2:(8-15).

[0010] Preferably, the aromatic group contained in the molecular structure of the reactive emulsifier includes a benzene ring.

[0011] Preferably, the hydrophilic group contained in the reactive emulsifier includes a sulfonic acid group.

[0012] Preferably, the reactive emulsifier includes at least one of sodium vinylbenzene sulfonate and sodium polystyrene sulfonate.

[0013] Preferably, the acrylic acid ester includes at least one of n-butyl acrylate, methyl methacrylate, isooctyl acrylate and isobornyl acrylate.

[0014] Preferably, the acrylate comprises n-butyl acrylate.

[0015] Preferably, the alcoholysis degree of polyvinyl alcohol is 75% to 100%, and the polymerization degree is 300 to 500. The alcoholysis degree of polyvinyl alcohol can be 78%, 88%, 98%, etc., but is not limited to the listed values, and other values ​​not listed in the numerical range are also applicable.

[0016] Preferably, the alcoholysis degree of the polyvinyl alcohol is 87% to 89%.

[0017] In the present invention, the degree of polymerization of polyvinyl alcohol has an important influence on the emulsion polymerization reaction and affects the performance of the polymer. The use of polyvinyl alcohol in this range in the emulsion polymerization reaction makes the monomers such as styrene in the reaction system have better stability, and effectively increases the interfacial tension and enhances the dispersibility of the dispersion system.

[0018] Preferably, in the raw materials for preparing the styrene acrylic emulsion, the content of the functional monomer is not 0, and the functional monomer includes acrylic acid; and / or, in the raw materials for preparing the styrene acrylic emulsion, the content of the crosslinking monomer is not 0, and the crosslinking monomer includes at least one of vinyl trimethoxy silane, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate. In the present invention, the emulsion polymerization reaction uses vinyl trimethoxy silane, trimethylolpropane trimethacrylate, and ethylene glycol dimethacrylate as crosslinking monomers, and by introducing functional groups such as silane groups, vinyl groups, and methacrylate groups into the polymer molecular chain, the linear high molecular long chain of the polymer can be formed into a crosslinked tight network structure, providing excellent hydrophobic properties and mechanical properties for the paint film formed by the emulsion.

[0019] Preferably, calculated by weight, the raw materials for preparing the above styrene-acrylic emulsion include 1 to 5 parts of functional monomers.

[0020] Preferably, calculated by weight, the raw materials for preparing the above styrene acrylic emulsion include 1 to 5 parts of crosslinking monomers.

[0021] Preferably, the initiator comprises sodium persulfate.

[0022] Preferably, the particle size of the styrene acrylic emulsion is 500 to 1000 nm.

[0023] Preferably, the particle size dispersion coefficient of the styrene acrylic emulsion is 0.108 to 0.142.

[0024] In the present invention, by adjusting the materials and material ratios used in the emulsion polymerization reaction, the particle size of the formed styrene-acrylic emulsion is smaller and the particle size distribution is relatively uniform, so that the emulsion exhibits higher stability.

[0025] Preferably, calculated by weight, the raw materials for preparing the above styrene-acrylic emulsion further include 0.2 to 2 parts of a molecular weight regulator.

[0026] Preferably, the molecular weight regulator comprises tert-dodecyl mercaptan.

[0027] According to another aspect of the present invention, there is provided a method for preparing a styrene-acrylic emulsion, comprising the following steps: S1. preparing a pre-emulsion, wherein the pre-emulsion contains styrene, acrylate, reactive emulsifier, functional monomer, cross-linking monomer, molecular weight regulator and initiator; S2. preparing a polyvinyl alcohol aqueous solution at a temperature of 80 to 90° C.; S3. heating the polyvinyl alcohol aqueous solution to 80 to 90° C., and under this temperature condition, adding the pre-emulsion to the polyvinyl alcohol aqueous solution, so that styrene, acrylate, reactive emulsifier, functional monomer and cross-linking monomer undergo polymerization reaction under the action of the initiator.

[0028] The invention adopts a heating self-reaction method to prepare the styrene-acrylic emulsion, the emulsion polymerization reaction is mild and stable, the process is simple, and the processing cost can be greatly reduced.

[0029] Preferably, after the preparation of the polyvinyl alcohol aqueous solution in step S2 is completed, the temperature is kept at 80 to 90° C. for 2 to 3 hours.

[0030] Preferably, the pre-emulsion in step S3 is added dropwise for 3 to 5 hours.

[0031] Preferably, after the polymerization reaction in step S3 is completed, the pH of the polymerization product is adjusted to 7 to 9. In this pH range, the storage stability of the styrene-acrylic emulsion prepared by the above scheme is further improved.

[0032] Preferably, in the above-mentioned method for preparing the styrene-acrylic emulsion, the initiator is added twice. In S1, a part of the initiator in the raw material is used to prepare the pre-emulsion, and the remaining part of the initiator is added to the polymerization reaction system in S3. The emulsion polymerization reaction rapidly promotes the nucleation of latex particles in the emulsion by adding the initiator twice, so that the styrene-acrylic emulsion has good stability during the polymerization reaction, which is conducive to controlling the size and size distribution of the emulsion particles.

[0033] Preferably, in S3 of the above method for preparing styrene-acrylic emulsion, the remaining part of the initiator is first added to the polyvinyl alcohol aqueous solution, and then the pre-emulsion is added.

[0034] Preferably, in the above-mentioned method for preparing styrene-acrylic emulsion, calculated by mass ratio, the initiator used to prepare the pre-emulsion in S1: the initiator added into the polymerization reaction system in S3 = 0.2-1: 0.1-0.2.

[0035] According to another aspect of the present invention, there is provided a latex powder, comprising a solid obtained by drying a styrene-acrylic emulsion. The latex powder has good dispersibility, and can be redispersed to obtain a styrene-acrylic emulsion with good film-forming effect, and the paint film formed by the styrene-acrylic emulsion has good hydrophobic properties.

[0036] Preferably, the latex powder further comprises at least one of polyvinyl alcohol, an anti-coagulant, a bactericide and a defoaming agent.

[0037] Preferably, the latex powder further comprises an anti-coagulation agent, which comprises at least one of calcium carbonate, clay, silicon dioxide, talcum powder and kaolin. The anti-coagulation agent can be matched with other components in the styrene acrylic emulsion to jointly improve the bonding strength, water resistance, construction performance and other properties of the latex powder.

[0038] Preferably, the weight ratio of the solid matter obtained after drying the styrene-acrylic emulsion to the polyvinyl alcohol is 100:(40-50).

[0039] Preferably, the weight ratio of the anti-coagulant, the bactericide and the defoaming agent is (4-5): (0.1-0.2): (0.1-0.2). DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only embodiments of a part of the present invention, rather than all embodiments.

[0041] Example 1

[0042] This embodiment provides a latex powder, and the specific preparation method is as follows:

[0043] (1) Preparation of styrene acrylic emulsion:

[0044] S1. 40 parts by weight of styrene, 55 parts by weight of acrylate, 2 parts by weight of reactive emulsifier, 2 parts by weight of functional monomer, 2 parts by weight of crosslinking monomer, 1 part by weight of initiator, 1 part by weight of molecular weight regulator and 50 parts by weight of deionized water were mixed and stirred to obtain a pre-emulsion; wherein the acrylate is n-butyl acrylate, the reactive emulsifier is sodium vinylbenzene sulfonate, the functional monomer is acrylic acid, the crosslinking monomer is vinyltrimethoxysilane, the initiator is sodium persulfate, and the molecular weight regulator is tert-dodecyl mercaptan;

[0045] S2. At a temperature of 80 ° C, 10 parts by weight of polyvinyl alcohol, 30 parts by weight of deionized water, and 0.5 parts by weight of baking soda were mixed and kept warm for 2 hours to obtain a polyvinyl alcohol aqueous solution; wherein the polyvinyl alcohol used has a degree of alcoholysis of 88% and a degree of polymerization of 300;

[0046] S3. The polyvinyl alcohol aqueous solution was heated to 80 ° C. Under this temperature condition, 0.1 parts by weight of sodium persulfate was added, and the pre-emulsion was added dropwise to the polyvinyl alcohol aqueous solution for 3 hours. After the reaction was completed, 1 part by weight of a 10% aqueous sodium hydroxide solution was added to the reaction system, and the pH of the polymerization product was adjusted to 8. The polymerization product was filtered using a 100-mesh steel mesh to obtain a styrene-acrylic emulsion;

[0047] The particle size of the prepared styrene-acrylic emulsion is 610 nm, and the particle size dispersion coefficient is 0.121.

[0048] (2) Preparation of latex powder:

[0049] 100 parts by weight of the above styrene-acrylic emulsion, 5 parts by weight of anti-coagulation agent, 40 parts by weight of polyvinyl alcohol aqueous solution, 0.2 parts by weight of bactericide and 0.2 parts of defoamer are mixed and atomized and dried to obtain latex powder.

[0050] Example 2

[0051] This embodiment provides a latex powder, and the specific preparation method is as follows:

[0052] (1) Preparation of styrene acrylic emulsion:

[0053] S1. 40 parts by weight of styrene, 55 parts by weight of acrylate, 2 parts by weight of reactive emulsifier, 2 parts by weight of functional monomer, 3 parts by weight of cross-linking monomer, 1 part by weight of initiator, 2 parts by weight of molecular weight regulator and 50 parts by weight of deionized water were mixed and stirred to obtain a pre-emulsion; wherein the acrylate is n-butyl acrylate, the reactive emulsifier is sodium polystyrene sulfonate, the functional monomer is acrylic acid, the cross-linking monomer is trimethylolpropane trimethacrylate, the initiator is sodium persulfate, and the molecular weight regulator is tert-dodecyl mercaptan;

[0054] S2. At a temperature of 85 ° C, 8 parts by weight of polyvinyl alcohol, 30 parts by weight of deionized water, 0.5 parts by weight of baking soda were mixed and kept warm for 2 hours to obtain a polyvinyl alcohol aqueous solution; wherein the polyvinyl alcohol used has a degree of alcoholysis of 88% and a degree of polymerization of 400;

[0055] S3. The polyvinyl alcohol aqueous solution was heated to 85 ° C. Under this temperature condition, 0.2 parts by weight of sodium persulfate was added, and the pre-emulsion was added dropwise to the polyvinyl alcohol aqueous solution for 4 hours. After the reaction was completed, 1 part by weight of a 10% aqueous sodium hydroxide solution was added to the reaction system, the pH of the polymerization product was adjusted to 8, and the polymerization product was filtered using a 100 mesh steel mesh to obtain a styrene-acrylic emulsion;

[0056] The particle size of the prepared styrene-acrylic emulsion is 700 nm, and the particle size dispersion coefficient is 0.108.

[0057] (2) Preparation of latex powder:

[0058] 100 parts by weight of the above styrene-acrylic emulsion, 4 parts by weight of anti-coagulation agent, 50 parts by weight of polyvinyl alcohol aqueous solution, 0.2 parts by weight of bactericide and 0.2 parts of defoamer are mixed and atomized and dried to obtain latex powder.

[0059] Example 3

[0060] This embodiment provides a latex powder, and the specific preparation method is as follows:

[0061] (1) Preparation of styrene acrylic emulsion:

[0062] S1. 50 parts by weight of styrene, 45.8 parts by weight of acrylate, 2 parts by weight of reactive emulsifier, 1 part by weight of functional monomer, 5 parts by weight of cross-linking monomer, 1 part by weight of initiator, 0.2 parts by weight of molecular weight regulator and 50 parts by weight of deionized water were mixed and stirred to obtain a pre-emulsion; wherein the acrylate is n-butyl acrylate, the reactive emulsifier is sodium polystyrene sulfonate, the functional monomer is acrylic acid, the cross-linking monomer is trimethylolpropane trimethacrylate, the initiator is sodium persulfate, and the molecular weight regulator is tert-dodecyl mercaptan;

[0063] S2. At a temperature of 90 ° C, 15 parts by weight of polyvinyl alcohol, 30 parts by weight of deionized water, 0.5 parts by weight of baking soda were mixed and kept warm for 2 hours to obtain a polyvinyl alcohol aqueous solution; wherein the polyvinyl alcohol used has a degree of alcoholysis of 88% and a degree of polymerization of 500;

[0064] S3. The polyvinyl alcohol aqueous solution was heated to 90 ° C. Under this temperature condition, 0.2 parts by weight of sodium persulfate was added, and the pre-emulsion was added dropwise to the polyvinyl alcohol aqueous solution for 5 hours. After the reaction was completed, 1 part by weight of a 10% aqueous sodium hydroxide solution was added to the reaction system, the pH of the polymerization product was adjusted to 7.5, and the polymerization product was filtered using a 100 mesh steel mesh to obtain a styrene-acrylic emulsion;

[0065] The particle size of the prepared styrene-acrylic emulsion is 680 nm, and the particle size dispersion coefficient is 0.142.

[0066] (2) Preparation of latex powder:

[0067] 100 parts by weight of the above styrene-acrylic emulsion, 5 parts by weight of an anti-coagulation agent, 40 parts by weight of a polyvinyl alcohol aqueous solution, 0.1 parts by weight of a bactericide and 0.1 parts by weight of a defoamer are mixed and atomized and dried to obtain latex powder.

[0068] Example 4

[0069] This embodiment provides a latex powder, which is different from that of Example 1 in that an equal amount of 1-allyloxy-3-(4-nonylphenol)-2-propanol polyoxyethylene (10) ether ammonium sulfate is used in the raw materials for preparing the styrene-acrylic emulsion in this embodiment to replace the sodium vinylbenzene sulfonate in Example 1. Except for the above differences, the materials, formula ratios and preparation operations used in the preparation of the latex powder in this embodiment are strictly consistent with those in Example 1.

[0070] The particle size of the prepared styrene-acrylic emulsion is 912 nm, and the particle size dispersion coefficient is 0.126.

[0071] Example 5

[0072] This embodiment provides a latex powder, and compared with the embodiment 1, the difference in composition is that in the raw materials used to prepare the styrene-acrylic emulsion, an equal weight portion of ethylene glycol dimethacrylate is used to replace the vinyl trimethoxysilane in the embodiment 1 as the cross-linking monomer required for preparing the styrene-acrylic emulsion. Except for the above difference, the materials, formula ratio and preparation operation used in this embodiment are strictly consistent with those in the embodiment 1.

[0073] The particle size of the prepared styrene-acrylic emulsion is 834 nm, and the particle size dispersion coefficient is 0.098.

[0074] Example 6

[0075] This embodiment provides a latex powder, and compared with the embodiment 1, the difference in composition is that in the raw materials used to prepare the styrene-acrylic emulsion, trimethylolpropane trimethacrylate is used in equal parts by weight to replace the vinyl trimethoxysilane in the embodiment 1 as the cross-linking monomer required for preparing the styrene-acrylic emulsion. Except for the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in the embodiment 1.

[0076] The particle size of the prepared styrene-acrylic emulsion is 784 nm, and the particle size dispersion coefficient is 0.151.

[0077] Example 7

[0078] This embodiment provides a latex powder, which is different from that of Example 1 in that the alcoholysis degree of the polyvinyl alcohol used in the raw materials for preparing the styrene-acrylic emulsion is 88% and the degree of polymerization is 400. Except for the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1.

[0079] The particle size of the prepared styrene-acrylic emulsion is 632 nm, and the particle size dispersion coefficient is 0.130.

[0080] Example 8

[0081] This embodiment provides a latex powder, and compared with Example 1, the difference in structure is that in step S1 of preparing styrene-acrylic emulsion in this embodiment, all the initiator sodium persulfate included in the raw materials participates in the preparation of the pre-emulsion, that is, all the sodium persulfate is added in S1. In addition to the above differences, the materials, formula ratios and preparation operations used in this embodiment are strictly consistent with those in Example 1. Specifically, the types of materials included in the raw materials for preparing styrene-acrylic emulsion in this embodiment and Example 11 and the corresponding weights of each material are consistent.

[0082] The particle size of the prepared styrene-acrylic emulsion is 1010 nm, and the particle size dispersion coefficient is 0.256.

[0083] Example 9

[0084] This embodiment provides a latex powder, and compared with the embodiment 1, the difference in composition is that in the raw materials used to prepare the styrene-acrylic emulsion, the weight fraction of the cross-linking monomer required for preparing the styrene-acrylic emulsion is 0. Except for the above difference, the materials, formula ratio and preparation operation used in this embodiment are strictly consistent with those in the embodiment 1.

[0085] The particle size of the prepared styrene-acrylic emulsion is 723 nm, and the particle size dispersion coefficient is 0.122.

[0086] Comparative Example 1

[0087] The latex powder provided in this comparative example is (VAE) 1100 latex powder from Dalian Chemical Industry.

[0088] Comparative Example 2

[0089] The latex powder provided in this comparative example is German Wacker 328N (VAE) rubber powder.

[0090] Comparative Example 3

[0091] This comparative example provides a latex powder, which is different from Example 1 in that, in the raw materials used to prepare the styrene-acrylic emulsion, an equal weight portion of sodium vinyl sulfonate is used to replace the sodium vinyl benzene sulfonate in Example 1 as a reactive emulsifier required for preparing the styrene-acrylic emulsion. Except for the above differences, the materials, formula ratios and preparation operations used in this example are strictly consistent with those in Example 1.

[0092] The particle size of the prepared styrene-acrylic emulsion is 2260 nm, and the particle size dispersion coefficient is 0.871.

[0093] Comparative Example 4

[0094] This comparative example uses Example 1 as a reference to prepare latex powder. In the process of preparing latex powder, this comparative example is different from Example 1 in that in the raw materials used to prepare styrene acrylic emulsion in this comparative example, an equal weight portion of sodium dodecylbenzene sulfonate is used to replace the sodium vinylbenzene sulfonate in Example 1. Except for the above differences, the materials, formula ratios and preparation operations used in the process of preparing latex powder in this comparative example are strictly consistent with those in Example 1.

[0095] The particle size of the prepared styrene-acrylic emulsion is 2010 nm, and the particle size dispersion coefficient is 0.541.

[0096] Comparative Example 5

[0097] This comparative example uses Example 1 as a reference to prepare latex powder. In the process of preparing latex powder, this comparative example is different from Example 1 in that in the raw materials used to prepare styrene-acrylic emulsion in this comparative example, an equal weight portion of combined emulsifier is used to replace the sodium vinylbenzene sulfonate in Example 1, wherein the combined emulsifier is a mixture of 2-acrylamide-2-methylpropane sulfonic acid sodium salt and allyl polyoxyethylene ether, and the weight ratio of 2-acrylamide-2-methylpropane sulfonic acid sodium salt to allyl polyoxyethylene ether is 1:1. In addition to the above differences, the materials, formula ratios and preparation operations used in the process of preparing latex powder in this comparative example are strictly consistent with those in Example 1.

[0098] The particle size of the prepared styrene-acrylic emulsion is 1540 nm, and the particle size dispersion coefficient is 0.377.

[0099] Test Case

[0100] 1. Participants

[0101] In this test example, the latex powders of Examples 1 to 9 and Comparative Examples 1 to 5 were used as test objects to conduct relevant performance tests.

[0102] 2. Test content

[0103] (1) Bond strength performance

[0104] With reference to JC / T 547-2017 Ceramic Tile Adhesive, the bonding strength performance of the cement-based adhesive prepared by the test subjects between ceramic tiles and concrete slabs was tested.

[0105] (2) Water absorption

[0106] With reference to JC / T 984-2011 Polymer Cement Waterproof Mortar, the water absorption rate of the polymer cement waterproof mortar prepared by the test object was tested after immersion in water at (20±2)℃ for 48h.

[0107] 3. Test results

[0108] Table 1 Test results of relevant properties of latex powder

[0109]

[0110]

[0111] The test results are shown in Table 1. In the standard curing strength test, the standard curing strength measured by the latex powder provided by Examples 1 to 9 and Comparative Examples 1 to 5 is in the range of 0.92 to 1.71 MPa, indicating that under normal temperature and moderate humidity, the above latex powders have good mechanical properties. However, the above latex powders show different relative sizes in the water curing strength and heat curing strength tests of this test example. In the water curing strength test, the water sample strength measured by the latex powder provided by Examples 1 to 9 is significantly higher than that of the latex powder provided by Comparative Examples 1 to 5. The reason for the above phenomenon is that in the process of preparing the latex powder, Examples 1 to 9 use a specific reactive emulsifier to participate in the emulsion polymerization reaction, thereby effectively improving the water resistance of the latex powder, thereby making the latex powder as the test object measured in the water sample strength test of this test example. Higher water sample strength value. Correspondingly, the water absorption test results of this test example show that the water absorption of the latex powder provided by Examples 1 to 9 is significantly lower than that of the latex powder provided by Comparative Examples 1 to 5. In addition, in the test of heat curing strength, among the latex powders provided in Comparative Examples 1 to 5, some of the test objects also showed low heat curing strength, such as the latex powders provided in Comparative Examples 3, 4, and 5, respectively, while the latex powders provided in Examples 1 to 9 can all achieve good heat curing strength values, indicating that they can still maintain good mechanical properties under high heat environments and have good heat resistance. In summary, the latex powders provided in Examples 1 to 9 can maintain good mechanical properties and have excellent water resistance under conventional application conditions, high humidity application conditions, and high temperature application conditions, while the water resistance of the latex powders provided in Comparative Examples 1 to 5 is poor, and it is difficult to maintain good mechanical properties under conventional application conditions, high humidity application conditions, and high temperature application conditions.

[0112] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention is described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A styrene acrylic emulsion, characterized in that: Calculated by weight, the raw materials include the following materials: 20-100 parts of styrene, 20-100 parts of acrylate, 0.5-2 parts of reactive emulsifier, 5-15 parts of polyvinyl alcohol, 0-5 parts of functional monomer, 0-5 parts of cross-linking monomer, 0.3-1.2 parts of initiator; The molecular structure of the reactive emulsifier includes an aromatic group and a carbon-carbon double bond structure.

2. The styrene-acrylic emulsion according to claim 1, characterized in that: The aromatic group contained in the molecular structure of the reactive emulsifier includes a benzene ring.

3. The styrene-acrylic emulsion according to claim 1, characterized in that: The hydrophilic group contained in the reactive emulsifier includes a sulfonic acid group.

4. The styrene-acrylic emulsion according to claim 1, characterized in that: The acrylic acid ester includes n-butyl acrylate.

5. The styrene-acrylic emulsion according to claim 1, characterized in that: The alcoholysis degree of the polyvinyl alcohol is 75% to 100%, and the polymerization degree is 300 to 500.

6. The styrene-acrylic emulsion according to claim 1, characterized in that: In the raw materials for preparing the styrene-acrylic emulsion, the content of the functional monomer is not 0, and the functional monomer includes acrylic acid; And / or, in the raw materials for preparing the styrene acrylic emulsion, the content of the cross-linking monomer is not 0, and the cross-linking monomer includes at least one of vinyl trimethoxy silane, trimethylol propane trimethacrylate, and ethylene glycol dimethacrylate.

7. The styrene-acrylic emulsion according to any one of claims 1 to 6, characterized in that: The particle size of the styrene acrylic emulsion is 500-1010 nm.

8. The styrene-acrylic emulsion according to claim 7, characterized in that: The particle size dispersion coefficient of the styrene-acrylic emulsion is 0.098-0.

256.

9. A method for preparing the styrene-acrylic emulsion according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. preparing a pre-emulsion, the pre-emulsion containing the styrene, the acrylate, the reactive emulsifier, the functional monomer, the cross-linking monomer and the initiator; S2. preparing a polyvinyl alcohol aqueous solution at a temperature of 80 to 90 ° C; S3. The polyvinyl alcohol aqueous solution is heated to 80-90° C., and under this temperature condition, the pre-emulsion is added to the polyvinyl alcohol aqueous solution to allow the styrene, the acrylate, the reactive emulsifier, the functional monomer, and the cross-linking monomer to undergo polymerization reaction under the action of the initiator.

10. A latex powder, characterized in that: The invention comprises a solid obtained by drying the styrene-acrylic emulsion as claimed in any one of claims 1 to 9.

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