Styrene butadiene latex and method for preparing the same, sealant

Abstract

The present application relates to the technical field of resin materials, in particular to a styrene-butadiene latex, a preparation method thereof and a sealant, and provides the styrene-butadiene latex with an average particle size of 180 nm to 500 nm; the volume ratio of latex particles with a particle size of greater than or equal to 250 nm in the styrene-butadiene latex is 41% to 70%, the volume ratio of latex particles with a particle size of less than or equal to 150 nm in the styrene-butadiene latex is 10% to 38%, the volume ratio of latex particles with a particle size of greater than 150 nm and less than 250 nm in the styrene-butadiene latex is 7% to 42%, and the solid content of the styrene-butadiene latex is greater than or equal to 67% and the viscosity at 25 DEG C is less than or equal to 2700 mPa s. The styrene-butadiene latex has the advantages of high solid content and low viscosity by reasonably matching the average particle size and the volume ratio of latex particles in the styrene-butadiene latex, and the styrene-butadiene latex is easy to be compounded with other binders to form a sealant product and is beneficial to shortening the curing rate of the sealant.

Description

Technical Field

[0001] This invention relates to the field of resin materials technology, and in particular to styrene-butadiene latex, its preparation method, and sealants. Background Technology

[0002] Styrene-butadiene rubber (SBR) latex is one of the important base materials for sealants. Due to its excellent flexibility, adhesion, weather resistance, and good compatibility with fillers / additives, SBR latex is widely used in elastic sealant formulations for building joints, automobiles, and industrial assembly. In sealant applications, the solid content and viscosity of the base material are among the core indicators determining product performance and production costs.

[0003] During the curing process of sealants, the evaporation of moisture or other volatile solvents and additives can cause significant volume shrinkage of the sealant film. High-solids latexes, with their lower moisture content, experience less water evaporation during film formation and curing, thus reducing the curing shrinkage rate of the sealant film and preventing cracking and delamination. Furthermore, the reduced water evaporation from high-solids latexes results in faster drying and curing of the formulated sealant, significantly improving production efficiency, rapidly forming a dense and continuous sealant film, and enhancing the cohesive strength and modulus of the cured sealant film.

[0004] Currently, while the solid content of styrene-butadiene rubber (SBR) latex can be increased to 60%–66% in related technologies, the extremely high volume fraction of latex particles and the extremely small distance between particles lead to a dramatic increase in van der Waals forces between them. At this point, the emulsifiers that maintain the stability of the latex particles in the SBR must withstand immense pressure, easily causing a sharp increase in viscosity and even irreversible aggregation or gelation of the SBR. Furthermore, excessively high viscosity of the SBR also significantly reduces its fluidity, making it impossible to blend with other base materials to form sealant products. Summary of the Invention

[0005] Based on this, the present invention provides a styrene-butadiene rubber latex, its preparation method, and a sealant. The styrene-butadiene rubber latex provided by the present invention, through reasonable formulation of its average particle size and the volume ratio of latex particles in the styrene-butadiene rubber latex, can achieve both high solids content and low viscosity; thus, it is easy to compound with other base materials to form sealant products, and it is beneficial to shorten the curing rate of the sealant.

[0006] In a first aspect, the present invention provides a styrene-butadiene latex, wherein the average particle size of the styrene-butadiene latex is 180 nm to 500 nm.

[0007] The volume percentage of latex particles with a diameter ≥250nm in the styrene-butadiene latex is 41%~70%. The volume percentage of latex particles with a diameter ≤150nm in the styrene-butadiene latex is 10%~38%. Furthermore, the volume percentage of latex particles with a diameter >150nm and a diameter <250nm in the styrene-butadiene latex is 7%~42%.

[0008] The solid content of the styrene-butadiene latex is ≥67%. The viscosity of the styrene-butadiene latex at 25°C is ≤2700 mPa·s.

[0009] In some embodiments, the average particle size of the styrene-butadiene rubber latex is 200 nm to 500 nm. The volume percentage of latex particles with a particle size ≥ 250 nm in the styrene-butadiene rubber latex is 50% to 70%. The solid content of the styrene-butadiene rubber latex is 67% to 72%. The viscosity of the styrene-butadiene rubber latex at 25°C is 180 mPa·s to 1100 mPa·s.

[0010] In some embodiments, the particle size distribution of the styrene-butadiene latex has a bimodal or multimodal distribution characteristic.

[0011] Optionally, the particle size distribution of the styrene-butadiene latex exhibits a first peak and a second peak. The peak particle size of the first peak is 40 nm to 110 nm. The peak particle size of the second peak is 250 nm to 960 nm.

[0012] A second aspect of the present invention provides a method for preparing styrene-butadiene latex, comprising the following steps:

[0013] A high-molecular-weight agglomerating agent is added to the first styrene-butadiene latex, and after mixing, diameter expansion, and concentration, a second styrene-butadiene latex is prepared.

[0014] The ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerating agent latex is 1:(0.6~1.4). The average particle size of the polymer agglomerating agent latex is 60nm~90nm.

[0015] The mass ratio of the solids in the first styrene-butadiene latex to the solids in the polymer agglomerating agent latex is 100:(0.3~5);

[0016] The average particle size of the second styrene-butadiene rubber latex is 180 nm to 500 nm. The volume percentage of latex particles with a diameter ≥ 250 nm in the second styrene-butadiene rubber latex is 41% to 70%. The volume percentage of latex particles with a diameter ≤ 150 nm in the second styrene-butadiene rubber latex is 10% to 38%. The volume percentage of latex particles with a diameter > 150 nm and < 250 nm in the second styrene-butadiene rubber latex is 7% to 42%. The solid content of the second styrene-butadiene rubber latex is ≥ 67%. The viscosity of the second styrene-butadiene rubber latex at 25°C is ≤ 2700 mPa·s.

[0017] In some embodiments, the average particle size of the styrene-butadiene latex is 200 nm to 500 nm. The solid content of the first styrene-butadiene latex is 25% to 45%. The solid content of the polymer agglomerating agent latex is 15% to 35%.

[0018] The volume percentage of latex particles with a particle size ≥250nm in the second styrene-butadiene latex is 50%~70%. The solid content of the second styrene-butadiene latex is 67%~72%. The viscosity of the second styrene-butadiene latex at 25℃ is 180mPa·s~1100mPa·s.

[0019] In some embodiments, the pH value of the first styrene-butadiene latex is 7.5-11. The pH value of the polymer agglomerating agent latex is 2-5.9.

[0020] In some embodiments, the temperature for mixing and expanding is 10°C to 45°C, and the time for mixing and expanding is 8 min to 360 min.

[0021] In some embodiments, the average particle size of the first styrene-butadiene latex is 50 nm to 150 nm.

[0022] In some embodiments, the copolymer mass ratio of butadiene to styrene in the first styrene-butadiene latex is (0.5~19):1.

[0023] In some embodiments, the preparation steps of the first styrene-butadiene latex include:

[0024] Butadiene, styrene, a first emulsifier, a first initiator and a first dispersion medium are mixed and subjected to a first polymerization reaction to prepare the first styrene-butadiene latex.

[0025] Optionally, the temperature for carrying out the first polymerization reaction is 70°C to 80°C.

[0026] Optionally, the mass ratio of butadiene to styrene is (0.5~19):1.

[0027] Optionally, the mass ratio of styrene to the first emulsifier is 1:(0.05~0.3).

[0028] Optionally, the mass ratio of styrene to the first initiator is 1:(0.005~0.15).

[0029] Optionally, the first emulsifier includes one or more of potassium stearate, potassium disproportionate, sodium dodecyl sulfate, polyethylene glycol octadecyl ether, and potassium palmitate.

[0030] Optionally, the first initiator includes one or more of potassium persulfate, tert-butanol peroxide, and azobisisobutyronitrile.

[0031] Optionally, the first dispersion medium includes water.

[0032] In some embodiments, the polymeric agglomerating latex is a copolymer containing carboxylic acid groups. The copolymer includes acrylic polymeric monomers and acrylate polymeric monomers.

[0033] Optionally, the acrylic polymer monomer includes one or more of methacrylic acid and acrylic acid.

[0034] Optionally, the acrylate polymer monomers include one or more of n-butyl acrylate and isooctyl acrylate.

[0035] Optionally, the copolymerization mass ratio of the acrylic polymer monomer and the acrylate polymer monomer is 1:(2~6).

[0036] In some embodiments, the preparation steps of the polymer agglomerating agent latex include:

[0037] After heating the emulsion, a second initiator is added, and then monomer replenishment liquid is continuously added within a time interval of ≤4 hours to carry out the second polymerization reaction and prepare the polymer agglomerator latex.

[0038] The emulsion includes a second dispersion medium, a second emulsifier, a molecular weight regulator, acrylic polymer monomers, and acrylate polymer monomers.

[0039] The monomer replenishment solution includes acrylic polymer monomers and acrylate polymer monomers;

[0040] Optionally, the second dispersion medium includes water;

[0041] Optionally, the second emulsifier includes one or more of potassium stearate, potassium disproportionated rosinate, sodium dodecyl sulfate, polyethylene glycol octadecyl ether, and potassium palmitate;

[0042] Optionally, the molecular weight regulator includes one or more of tert-dodecyl mercaptan and n-octyl mercaptan;

[0043] Optionally, the second initiator includes one or more of potassium persulfate, tert-butanol peroxide, and azobisisobutyronitrile;

[0044] Optionally, the ratio of the sum of the mass of the acrylic polymer monomers included in the emulsion and the monomer replenishment liquid to the sum of the mass of the acrylate polymer monomers included in the emulsion and the monomer replenishment liquid is 1:(2~6).

[0045] Optionally, the mass ratio of the acrylic polymer monomer included in the emulsion to the mass of the acrylic polymer monomer included in the monomer replenishment liquid is 1:(0.5~4);

[0046] Optionally, the mass ratio of the acrylate polymer monomers included in the emulsion to the mass of the acrylate polymer monomers included in the monomer replenishment liquid is 1:(0.4~2).

[0047] Optionally, the mass ratio of the acrylic polymer monomer to the second emulsifier in the emulsion is 1:(0.3~1);

[0048] Optionally, the mass ratio of the acrylic polymer monomer to the molecular weight regulator in the emulsion is 1:(0.03~0.08);

[0049] Optionally, the mass ratio of the acrylic polymer monomers in the emulsion to the acrylate polymer monomers in the emulsion is 1:(4~6);

[0050] Optionally, the mass ratio of the acrylic polymer monomer in the monomer replenishment solution to the acrylate polymer monomer in the monomer replenishment solution is 1:(2~5).

[0051] A third aspect of the present invention provides a sealant comprising styrene-butadiene latex as described in any one of the first aspects of the present invention; or comprising styrene-butadiene latex prepared by any one of the preparation methods of the second aspect of the present invention.

[0052] The technical solution provided by this invention has at least the following beneficial effects:

[0053] By properly combining the average particle size and the volume ratio of latex particles in styrene-butadiene latex, styrene-butadiene latex can have the advantages of both high solids content and low viscosity. A graded particle size distribution is adopted, which combines large-diameter latex particles with a particle size ≥250nm and small-diameter latex particles with a particle size ≤150nm in a specific volume proportion. With the synergy of medium-diameter latex particles with a particle size >150nm and <250nm in a specific volume proportion, the large-diameter and small-diameter latex particles in a specific volume proportion are staggered. The medium-diameter latex particles can fill the gaps between the large-diameter latex particles, while also dispersing and isolating the small-diameter latex particles, thus preventing the local agglomeration of small-diameter latex particles in the gaps between large-diameter latex particles. The combination of latex particles of different particle sizes in the above-mentioned styrene-butadiene latex can weaken the effective interaction force between particles, thereby avoiding the increase in viscosity of the styrene-butadiene latex system and the phenomenon of latex particle agglomeration and gelation, achieving a stable low viscosity of the styrene-butadiene latex system with high solids content.

[0054] Furthermore, the aforementioned styrene-butadiene latex has the advantages of high solids content and low viscosity, and is also easy to blend with other base materials to form sealant products, and is conducive to shortening the curing rate of sealants. Attached Figure Description

[0055] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0056] Figure 1 This is a particle size distribution diagram of latex particles in the styrene-butadiene latex prepared in Example 2.

[0057] Figure 2 The particle size distribution diagram of latex particles in the styrene-butadiene latex prepared in Example 4 is shown.

[0058] Figure 3 The particle size distribution diagram of latex particles in the styrene-butadiene latex prepared in Example 6 is shown.

[0059] Figure 4 The particle size distribution diagram of latex particles in the styrene-butadiene latex prepared in Comparative Example 5 is shown. Detailed Implementation

[0060] The following detailed description, in conjunction with specific embodiments, provides a more complete and clear account of styrene-butadiene latex, its preparation method, and the sealant. This invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this invention.

[0061] Styrene-butadiene rubber latex is one of the important base materials for sealants. With its excellent flexibility, adhesion and weather resistance, it can significantly improve the elastic recovery ability and interfacial adhesion of sealants. At the same time, it has good compatibility with fillers and additives, and is suitable for sealing needs in various scenarios such as construction, industry and automobiles.

[0062] The high solids content of styrene-butadiene rubber (SBR) latex can reduce the moisture content of the system, shorten the curing cycle of sealants, and reduce construction shrinkage. Traditional SBR latex has a solids content of approximately 45%–55%. To further improve the high solids content of SBR latex, one approach is to use quaternized cage-like silsesquioxanes (POSS) to adjust the particle size, concentrating it to approximately 63% solids content. However, this approach cannot further increase the solids content of SBR latex. Furthermore, due to the extremely high volume fraction of latex particles at higher solids content, the strong van der Waals attraction between latex particles leads to a sharp increase in latex viscosity, decreased system stability, and a high tendency for latex particles to aggregate or gel, making it difficult to provide SBR latex with both high solids content and lower viscosity.

[0063] Another approach involves using compound viscosity reducers to lower the viscosity of styrene-butadiene latex, allowing it to be concentrated to a solid content of 62%–66%. However, adding viscosity reducers can reduce the space occupied by other components, weakening the mechanical strength, adhesion, and weather resistance of the sealant film. Furthermore, viscosity reducers are prone to precipitation, which can easily cause shrinkage and cracking of the sealant film.

[0064] Therefore, how to provide a styrene-butadiene latex that has both low viscosity and high solids content, making it suitable for sealants, has become a technical problem that urgently needs to be solved at this stage.

[0065] In a first aspect, the present invention provides a styrene-butadiene rubber latex, wherein the average particle size of the styrene-butadiene rubber latex is 180 nm to 500 nm; the volume percentage of latex particles with a particle size ≥ 250 nm in the styrene-butadiene rubber latex is 41% to 70%; further, the volume percentage of latex particles with a particle size ≤ 150 nm in the styrene-butadiene rubber latex is 10% to 38%, and the volume percentage of latex particles with a particle size > 150 nm and a particle size < 250 nm in the styrene-butadiene rubber latex is 7% to 42%.

[0066] In some embodiments, the solid content of styrene-butadiene latex is ≥67%; the viscosity of styrene-butadiene latex at 25°C is ≤2700 mPa·s.

[0067] In this invention, unless otherwise specified, "solid content" or "solid percentage" in latex or solution refers to the percentage of the mass of non-volatile solid components in the latex or solution relative to the total mass. Furthermore, the solid content involved in this invention can be measured using a Mettler moisture meter. In this invention, viscosity can be measured using a Mettler rotational viscometer.

[0068] In this invention, "particle size" refers to the diameter of latex particles. "Average particle size" refers to the average diameter of latex particles. Unless otherwise specified, the average particle size in this invention refers to the Z-average particle size. The Z-average particle size refers to the intensity-weighted average hydrodynamic particle size measured using dynamic light scattering. The testing instrument may include, but is not limited to, the Malvern Zetasizer Nano.

[0069] By rationally combining the average particle size and the volume percentage of latex particles in styrene-butadiene rubber (SBR) latex, SBR latex can possess the advantages of both high solids content and low viscosity. The average particle size of SBR latex is 180nm~500nm, while controlling the volume percentage of large-diameter latex particles (≥250nm) to be 41%~70%, the volume percentage of small-diameter latex particles (≤150nm) to be 10%~38%, and the volume percentage of latex particles with a particle size >150nm and <250nm to be 7%~42%. The combination of large and small latex particles with specific volume proportions and particle sizes, with large particles forming the main body and small particles filling the gaps between them, optimizes the spatial distribution of particles through staggered arrangement. Medium-sized latex particles can fill the gaps between large particles, while simultaneously providing uniform dispersion and isolation for small particles, preventing localized aggregation of small latex particles within the gaps between large particles. This combination of latex particles with varying particle sizes in the aforementioned styrene-butadiene rubber latex effectively increases the average spacing between large and small particles, thereby weakening the effective interparticle interactions and preventing increased viscosity and latex particle agglomeration in the styrene-butadiene rubber latex system. This achieves a stable, low viscosity styrene-butadiene rubber latex system with high solids content. Furthermore, this invention enables styrene-butadiene latex to possess both high solids content and low viscosity without the use of viscosity reducers. This also avoids the problem of component space occupancy caused by the addition of viscosity reducers, which affects the mechanical strength, adhesion, and weather resistance of the sealant film.

[0070] Therefore, the aforementioned styrene-butadiene latex has the advantages of high solids content and low viscosity, making it easy to blend with other base materials to form sealant products, and it also helps to shorten the curing rate of the sealant.

[0071] The average particle size of styrene-butadiene rubber latex can be, but is not limited to, 180nm, 200nm, 260nm, 270nm, 271nm, 272nm, 275nm, 277nm, 278nm, 280nm, 300nm, 490nm, or 500nm, or any two of the above values ​​as endpoints. Further, the average particle size of styrene-butadiene rubber latex can be 200nm to 500nm. Even further, the average particle size of styrene-butadiene rubber latex can be 270nm to 500nm.

[0072] The volume percentage of latex particles with a diameter ≥250nm in styrene-butadiene rubber latex can be, but is not limited to, 41%, 42%, 45%, 48%, 50%, 51%, 52%, 55%, 58%, 59%, 60%, 61%, 65%, 68%, or 70%, or any two of the above values ​​as endpoints. Further, the volume percentage of latex particles with a diameter ≥250nm in styrene-butadiene rubber latex can be 50%~70%. Even further, the volume percentage of latex particles with a diameter ≥250nm in styrene-butadiene rubber latex can be 60%~70%.

[0073] The volume percentage of latex particles with a particle size ≤150nm in styrene-butadiene rubber latex can be, but is not limited to, 10%, 12%, 15%, 18%, 20%, 21%, 22%, 28%, 29%, 30%, 31%, 32%, 33%, 35%, 36%, or 38%, or any two of the above values ​​as endpoints. Further, the volume percentage of latex particles with a particle size ≤150nm in styrene-butadiene rubber latex can be 10% to 21%.

[0074] The volume percentage of latex particles with a diameter >150 nm and a diameter <250 nm in styrene-butadiene rubber latex can be, but is not limited to, 7%, 8%, 9%, 12%, 13%, 15%, 19%, 20%, 21%, 25%, 30%, 35%, 38%, 40%, or 42%, or any two of the above values ​​as endpoints. In some examples, the average particle size of the styrene-butadiene rubber latex can be 200 nm to 500 nm. The volume percentage of latex particles with a diameter ≥250 nm in the styrene-butadiene rubber latex can be 50% to 70%. The above-mentioned proportion of large-diameter latex particles can optimize the packing structure, reduce the interaction between latex particles, and inhibit the agglomeration of small latex particles, thereby further reducing the viscosity of the styrene-butadiene rubber latex.

[0075] For example, the solid content of styrene-butadiene latex is 67% to 72%. The viscosity of styrene-butadiene latex at 25°C is 180 mPa·s to 1100 mPa·s. As an example, the solid content of styrene-butadiene latex may include, but is not limited to, 67%, 68%, 69%, 70%, 71%, or 72%, or any two of the above values ​​as endpoints. The viscosity of styrene-butadiene latex at 25°C may include, but is not limited to, 180 mPa·s, 200 mPa·s, 210 mPa·s, 220 mPa·s, 230 mPa·s, 240 mPa·s, 280 mPa·s, 300 mPa·s, 360 mPa·s, 380 mPa·s, 390 mPa·s, 410 mPa·s, 420 mPa·s, 480 mPa·s, 800 mPa·s, 880 mPa·s, 890 mPa·s, 900 mPa·s, 1000 mPa·s, 1090 mPa·s, or 1100 mPa·s, or any two of the above values ​​as endpoints.

[0076] In some examples, the particle size distribution of styrene-butadiene rubber latex exhibits a bimodal or multimodal distribution characteristic. That is, it displays bimodal or multimodal characteristics. A bimodal or multimodal distribution refers to the particle size distribution curve showing two or more peaks. Further, multimodal characteristics refer to the presence of three or more peaks in the particle size distribution map of the styrene-butadiene rubber latex.

[0077] Furthermore, the particle size distribution of styrene-butadiene latex exhibits a first peak and a second peak. For example, the peak particle size of the first peak can be 40 nm to 110 nm. For example, the peak particle size of the second peak can be 250 nm to 960 nm. More exemplaryly, the peak particle size of the first peak can be 50 nm to 106 nm, and the peak particle size of the second peak can be 255 nm to 955 nm.

[0078] The latex particles in styrene-butadiene rubber latex exhibit a bimodal or multimodal particle size distribution, and are matched with large, medium, and small latex particles of a specific volume ratio and particle size. By optimizing the spatial arrangement, it is easy to weaken the interaction between large and small latex particles, thereby inhibiting the increase in system viscosity and allowing styrene-butadiene rubber latex to maintain low viscosity characteristics under high solid content conditions.

[0079] In this invention, unless otherwise specified, "particle size distribution map" refers to a particle size distribution spectrum obtained by using the dynamic light scattering method. The horizontal axis of the "particle size distribution map" corresponds to the latex particle diameter, and the vertical axis corresponds to the volume percentage of the latex particles. The testing instrument may include, but is not limited to, the Malvern Zetasizer Nano.

[0080] For the preparation of styrene-butadiene rubber latex, some technologies utilize a co-polymerization process involving large-seed and small-seed emulsions to prepare ultra-high solids latex for latex foaming. The large-seed emulsion comprises styrene, an emulsifier, and a catalyst; the small-seed emulsion also comprises styrene, an emulsifier, and a catalyst. This method first prepares a pre-emulsion using styrene and butadiene, then adds the large-seed and small-seed emulsions, followed by stirring, heating, and incubation. Therefore, this method requires a three-stage styrene-butadiene copolymerization operation. This process is relatively complex, and due to differences in the copolymerization reactivity ratios of styrene-butadiene, multi-stage polymerization can easily lead to significant deviations in the styrene-butadiene copolymer ratio in the latex. This can result in inconsistent shrinkage rates when used in sealants, leading to decreased sealing performance. Therefore, achieving stable preparation of ultra-high solids latex based on a single styrene-butadiene latex copolymerization operation is of great significance for improving the competitiveness of sealant products.

[0081] Based on this, a second aspect of the present invention provides a method for preparing styrene-butadiene latex, comprising the following steps: adding a polymer agglomerating agent latex to a first styrene-butadiene latex, and after mixing, diameter expansion, and concentration, preparing a second styrene-butadiene latex.

[0082] In some embodiments, the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerating agent latex is 1:(0.6~1.4); the average particle size of the polymer agglomerating agent latex is 60nm~90nm.

[0083] In some further embodiments, the mass ratio of the solids in the first styrene-butadiene latex to the solids in the polymer agglomerator latex is 100:(0.3~5).

[0084] Understandably, the preparation method provided in the second aspect of the present invention can be used to prepare the styrene-butadiene latex of the first aspect of the present invention. Furthermore, since concentration only involves the removal of moisture or volatile components, the properties of the concentrated styrene-butadiene latex and the mixed and expanded styrene-butadiene latex are essentially the same, except for the difference in solid content and the ion concentration caused by the change in solid content. Unless otherwise specified, the concentration temperature of the present invention is 30℃~80℃. More specifically, unless otherwise specified, the concentration temperature is 60℃. Exemplarily, the average particle size of the second styrene-butadiene latex is 180nm~500nm. The volume percentage of latex particles with a particle size ≥250nm in the second styrene-butadiene latex is 41%~70%. The volume percentage of latex particles with a particle size ≤150nm in the second styrene-butadiene latex is 10%~38%. The volume percentage of latex particles with a particle size >150nm and <250nm in the second styrene-butadiene latex is 7%~42%. The solid content of the second styrene-butadiene latex is ≥67%. The viscosity of the second styrene-butadiene latex at 25°C is ≤2700 mPa·s.

[0085] In the preparation method provided by the second aspect of the present invention, the average particle size of the polymer agglomerator latex, the mass ratio of solid matter in the first styrene-butadiene latex to the mass ratio of solid matter in the polymer agglomerator latex can regulate the number of particles participating in polymerization. This, combined with the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerator latex, can constrain the particle size after latex particle expansion. Finally, the average particle size of the styrene-butadiene latex, the volume percentage of latex particles with a particle size ≥250 nm, the volume percentage of latex particles with a particle size ≤150 nm, and the volume percentage of latex particles with a particle size >150 nm and <250 nm are adjusted to form a styrene-butadiene latex with a well-defined particle size distribution, which weakens the interaction between latex particles. The styrene-butadiene latex prepared in this way has high solids content and low viscosity.

[0086] Furthermore, the preparation method provided by the present invention only requires a single mixing and expansion of the first styrene-butadiene latex and the polymer agglomerating agent latex to obtain a styrene-butadiene latex with high solid content and low viscosity. This avoids the problem of large deviations in the styrene-butadiene copolymerization ratio caused by multi-stage polymerization in traditional methods, which leads to a decrease in the sealing performance of the sealant.

[0087] The ratio of the average particle size of the first styrene-butadiene rubber latex to the average particle size of the polymer agglomerating agent latex can be, but is not limited to, 1:0.6, 1:0.7, 1:0.78, 1:0.8, 1:0.85, 1:0.87, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, or 1:1.4, or any two of the above values ​​as endpoints. The ratio of the average particle size of the first styrene-butadiene rubber latex to the average particle size of the polymer agglomerating agent latex can be 1:(0.6~1.1).

[0088] The ratio of the average particle size of the first styrene-butadiene rubber latex to the average particle size of the polymer agglomerator latex plays a crucial role in controlling the particle size of the second styrene-butadiene rubber latex. This invention has found that when the ratio of the average particle size of the first styrene-butadiene rubber latex to the average particle size of the polymer agglomerator latex is large or small, it affects the proportion of latex particles with a particle size ≤150nm and latex particles with a particle size ≥250nm, thereby leading to a higher viscosity of the second styrene-butadiene rubber latex.

[0089] In some examples, the average particle size of the polymer agglomerating agent latex is 60 nm to 90 nm. Exemplarily, the average particle size of the polymer agglomerating agent latex may include, but is not limited to, 60 nm, 65 nm, 70 nm, 75 nm, 80 nm, 85 nm, or 90 nm, or any two of the above values ​​as endpoints. Further, the average particle size of the polymer agglomerating agent latex may be 70 nm to 90 nm.

[0090] When the average particle size of the polymer agglomerating agent latex is within the above-mentioned range, the degree of agglomeration can be controlled under the synergistic effect of the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerating agent latex, and the mass ratio of the solid matter in the first styrene-butadiene latex to the solid matter in the polymer agglomerating agent latex. This allows the first styrene-butadiene latex to exhibit differentiated agglomeration, thereby producing latex particles with large, medium, and small particle sizes in specific volume proportions. This optimizes the particle packing structure and weakens the interparticle interaction forces. Consequently, it effectively reduces the viscosity of the second styrene-butadiene latex while inhibiting latex particle agglomeration and gelation, ensuring the stability of the latex system under high solid content.

[0091] As an example, the mass ratio of solids in the first styrene-butadiene latex to solids in the polymer agglomerating agent latex may include, but is not limited to, 100:0.3, 100:0.5, 100:0.8, 100:1, 100:1.1, 100:1.5, 100:1.7, 100:1.8, 100:1.9, 100:2, 100:2.1, 100:2.2, 100:3, 100:4, 100:4.8, or 100:5, or any two of the above values ​​as endpoints within a range. The mass ratio of solids in the first styrene-butadiene latex to solids in the polymer agglomerating agent latex may be 100:(2~5).

[0092] When the mass ratio of solids in the first styrene-butadiene latex to solids in the polymer agglomerator latex is too high, the latex particles agglomerate and grow excessively. As a result, the average particle size of the second styrene-butadiene latex prepared under these conditions is relatively high, and the volume proportion of latex particles with a particle size ≥250nm in the second styrene-butadiene latex exceeds 70%, while the volume proportion of small-diameter latex particles with a particle size ≤150nm is insufficient. The particle size classification ratio is unbalanced, which prevents the styrene-butadiene latex from having both the advantages of high solids content and low viscosity.

[0093] In some examples, the pH value of the first styrene-butadiene latex is 7.5–11. The pH value of the polymer agglomerator latex is 2–5.9. The pH values ​​of the first and polymer agglomerator latexes within these ranges affect their surface charges, altering the interparticle interactions and thus regulating the particle size expansion process to obtain a second styrene-butadiene latex with well-defined particle size distribution.

[0094] As an example, the pH value of the first styrene-butadiene latex can be, but is not limited to, 7.5, 7.6, 7.8, 8, 9, 9.8, 10, 10.2, 10.5, 10.8, or 11, or any two of the above values ​​as endpoints. This invention has found that when the pH value of the first styrene-butadiene latex is outside the above range, the surface charge of the particles becomes unbalanced, making the diameter expansion reaction difficult to proceed smoothly and controllably, leading to a paste-like phenomenon during the mixing and diameter expansion of the styrene-butadiene latex. Further, the pH value of the first styrene-butadiene latex can be 7.5 to 10.

[0095] The pH value of the polymer agglomerating agent latex may include, but is not limited to, 2, 2.2, 2.5, 3, 4, 4.5, 4.8, 5, 5.2, 5.5, 5.8, or 5.9, or any two of the above values ​​as endpoints. Further, the pH value of the polymer agglomerating agent latex may be 5 to 5.8.

[0096] The pH value of the aforementioned polymer agglomerating agent latex is matched with that of the first styrene-butadiene latex, which can regulate the degree of latex particle agglomeration and growth, as well as the particle size distribution. If the pH value of the polymer agglomerating agent latex deviates from the above range, it will lead to a decrease in the average particle size of the styrene-butadiene latex, with the volume ratio of latex particles with a diameter ≤150nm exceeding 90%. Due to the excessively high proportion of small-diameter latex particles, the particle contact area increases significantly, the intermolecular forces are significantly enhanced, the system fluidity deteriorates, and further increases in solid content will easily lead to paste formation and agglomeration.

[0097] Furthermore, to achieve good flowability of the first styrene-butadiene latex and facilitate smooth subsequent mixing and diameter expansion, in some examples, the solid content of the first styrene-butadiene latex is 25% to 45%. Exemplarily, the solid content of the first styrene-butadiene latex may include, but is not limited to, 25%, 26%, 28%, 30%, 33%, 34%, 35%, 36%, 40%, 43%, 44%, or 45%. Further, the solid content of the second styrene-butadiene latex may be 25% to 35%.

[0098] As an example, the solid content of the polymer agglomerating agent latex is 12% to 35%. The solid content of the polymer agglomerating agent latex can be, but is not limited to, 12%, 15%, 16%, 20%, 23%, 25%, 26%, 28%, 30%, 34%, or 35%, or any two of the above values ​​as endpoints. Further, the solid content of the polymer agglomerating agent latex can be 15% to 35%. Even further, the solid content of the polymer agglomerating agent latex can be 25% to 35%.

[0099] The solid content of the first styrene-butadiene latex and the polymer agglomerator latex plays a crucial role in regulating the agglomeration between latex particles. This invention reveals that a low solid content in the polymer agglomerator latex results in a low average particle size of the styrene-butadiene latex, with the volume percentage of latex particles ≥250nm in the styrene-butadiene latex being less than 50%. This imbalance in the particle size distribution ultimately leads to an increase in the viscosity of the styrene-butadiene latex. For example, the solid content of the first styrene-butadiene latex is matched with that of the second styrene-butadiene latex, resulting in an average particle size of 200nm~500nm and a volume percentage of latex particles ≥250nm in the second styrene-butadiene latex of 50%~70%, thereby obtaining a second styrene-butadiene latex with a solid content of 67%~72% and a viscosity of 180mPa·s~1100mPa·s at 25°C.

[0100] As mentioned above, the average particle size of the first styrene-butadiene latex and the average particle size of the polymer agglomerator latex refer to the average diameter of the latex particles therein. Unless otherwise specified, the average particle size of this invention refers to the Z-average particle size. The Z-average particle size refers to the intensity-weighted average hydrodynamic particle size measured by dynamic light scattering. The testing instrument may include, but is not limited to, the Malvern Zetasizer Nano.

[0101] As an example, the preparation of the first styrene-butadiene latex and the mixing and diameter expansion process in this invention can be referred to relevant technologies in the art. For example, the preparation process of the first styrene-butadiene latex can be referred to pages 94-123 of the book "Emulsion Polymerization of Styrene-Butadiene Rubber" written by Liu Dahua et al. The mixing and diameter expansion process can be referred to "Artificial neural network prediction of particle size of agglomerated polybutadiene latex".

[0102] In some examples, the mixing and expansion temperature is 10°C to 45°C. The mixing and expansion time is 8 min to 360 min. Exemplarily, the mixing and expansion temperature can be, but is not limited to, 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, or 45°C, or any two of the above values ​​as endpoints. The mixing and expansion time can be, but is not limited to, 8 min, 10 min, 12 min, 15 min, 18 min, 20 min, 22 min, 25 min, 28 min, 30 min, 32 min, 35 min, 60 min, 80 min, 100 min, 200 min, 300 min, 320 min, 330 min, or 360 min, or any two of the above values ​​as endpoints.

[0103] Controlling the mixing and expansion temperature between 10℃ and 45℃ and the time between 8 min and 360 min ensures a mild and controllable agglomeration reaction. This temperature range avoids latex particle agglomeration caused by slightly higher temperatures and also prevents slightly lower temperatures from resulting in a slower agglomeration rate and uneven agglomeration. This combination of mixing and expansion temperature and mixing time allows the polymer agglomerant to fully contact the styrene-butadiene latex, achieving uniform and differentiated agglomeration and precisely forming large, medium, and small latex particles with the target volume percentage. Ultimately, this results in a stable latex particle size distribution and controllable viscosity.

[0104] The properties of styrene-butadiene latex are illustrated below with some examples.

[0105] In some examples, the average particle size of the first styrene-butadiene rubber latex is 50 nm to 150 nm. Exemplarily, the average particle size of the first styrene-butadiene rubber latex may include, but is not limited to, 50 nm, 52 nm, 55 nm, 60 nm, 70 nm, 73 nm, 74 nm, 75 nm, 80 nm, 90 nm, 100 nm, 140 nm, or 150 nm, or any two of the above values ​​as endpoints. Further, the average particle size of the first styrene-butadiene rubber latex may be 75 nm to 150 nm.

[0106] In some examples, the copolymer mass ratio of butadiene to styrene in the first styrene-butadiene latex is (0.5~19):1. The copolymer mass ratio of butadiene to styrene in the first styrene-butadiene latex may include, but is not limited to, 0.5:1, 0.6:1, 1:1, 2:1, 2.8:1, 2.9:1, 3:1, 3.5:1, 5:1, 10:1, 18:1 or 19:1, or any two of the above values ​​as endpoints within a range.

[0107] In some examples, the preparation steps of the first styrene-butadiene latex include: mixing butadiene, styrene, a first emulsifier, a first initiator, and a first dispersion medium, and carrying out a first polymerization reaction to prepare the first styrene-butadiene latex. Further, the butadiene is 1,3-butadiene.

[0108] In some of these examples, the mass ratio of butadiene to styrene is (0.5~19):1. Understandably, the mass ratio of butadiene to styrene in the first styrene-butadiene latex preparation step is similar to the copolymerization mass ratio of butadiene to styrene in the first styrene-butadiene latex.

[0109] As an example, the first emulsifier includes one or more of potassium stearate, potassium disproportionate, sodium lauryl sulfate, polyethylene glycol octadecyl ether, and potassium palmitate. Further, the first emulsifier includes potassium stearate and potassium disproportionate in a mass ratio of (1.3~1.4):1.

[0110] In some examples, the mass ratio of styrene to the first emulsifier is 1:(0.05~0.3). The mass ratio of styrene to the first emulsifier may include, but is not limited to, 1:0.05, 1:0.07, 1:0.09, 1:0.1, 1:0.2, 1:0.23, 1:0.24, 1:0.25 or 1:0.3, or any two of the above values ​​as endpoints.

[0111] As an example, the first initiator includes one or more of potassium persulfate, tert-butanol peroxide, and azobisisobutyronitrile. Further, the first initiator includes potassium persulfate. In some examples, the mass ratio of styrene to the first initiator is 1:(0.005~0.15). The mass ratio of styrene to the first initiator may include, but is not limited to, 1:0.075, 1:0.02, 1:0.1, 1:0.12, 1:0.13, or 1:0.15, or a range formed by any two of the above point values ​​as endpoints.

[0112] As an example, the first dispersion medium includes water. It can further be water. Understandably, the amount of the first dispersion medium added can be controlled according to the solid content of the first styrene-butadiene latex. Furthermore, a pH adjuster and a salting agent may optionally be added during the preparation step of the first styrene-butadiene latex. The pH adjuster may include, but is not limited to, one or more of potassium hydroxide and acetic acid. The salting agent may include, but is not limited to, one or more of potassium carbonate, potassium hydroxide, and potassium chloride. Understandably, the amount of the pH adjuster added can be controlled according to the pH value of the first styrene-butadiene latex.

[0113] In some examples, the temperature for the first polymerization reaction is 70°C to 80°C. Exemplarily, the temperature for the first polymerization reaction may include, but is not limited to, 70°C, 75°C, or 80°C, or any two of these values ​​as endpoints. Further, the duration of the first polymerization reaction can be determined based on the conversion rates of butadiene and styrene. Exemplarily, the first polymerization reaction can be terminated when the conversion rate of butadiene and styrene is ≥95%. Even further, the conversion rate can be calculated by separately detecting the mass of residual styrene and 1,3-butadiene monomers in the system using gas chromatography, and the difference between the total feed butadiene and styrene monomers and the residual monomers. Conversion rate X = (m... 总投料 -m 残存 ) / m 总投料 ×100%. m 总投料 This represents the total mass of butadiene and styrene fed into the plant. (m) 残存 The total mass of styrene and 1,3-butadiene monomers remaining in the system.

[0114] The properties of polymer agglomerate latex are illustrated below with some examples.

[0115] In some of these examples, the polymeric agglomerate latex is a copolymer containing carboxylic acid groups. The copolymer includes acrylic polymeric monomers and acrylate polymeric monomers.

[0116] In some of these examples, the acrylic polymer monomers include one or more of methacrylic acid and acrylic acid.

[0117] In some of these examples, the acrylate polymer monomers include one or more of n-butyl acrylate and isooctyl acrylate.

[0118] In some examples, the copolymerization mass ratio of acrylic monomers to acrylate monomers is 1:(2~6). Exemplarily, the copolymerization mass ratio of acrylic monomers to acrylate monomers may include, but is not limited to, 1:3, 1:5.5, 1:5.67, 1:5.7 or 1:6, or any two of the above point values ​​as endpoints.

[0119] In some of these examples, the preparation method of the polymer agglomerating agent latex can be referred to CN101754982A.

[0120] In some examples, the preparation steps of the polymer agglomerating agent latex include: heating the emulsion and adding a second initiator, followed by continuously adding monomer replenishment liquid at time intervals of ≤4h to carry out a second polymerization reaction and prepare the polymer agglomerating agent latex.

[0121] In some embodiments, the emulsion includes a second dispersion medium, a second emulsifier, a molecular weight regulator, acrylic polymeric monomers, and acrylate polymeric monomers. The monomer replenishment solution includes acrylic polymeric monomers and acrylate polymeric monomers.

[0122] In some examples, the second dispersion medium includes water. Understandably, a third dispersion medium may also be included in the monomer replenishment solution. The third dispersion medium includes water. In the preparation steps of the polymer agglomerate latex, the amounts of the second and third dispersion media added can be controlled according to the solid content of the polymer agglomerate latex.

[0123] Non-limitingly, the second emulsifier may include one or more of potassium stearate, potassium disproportionated rosinate, sodium dodecyl sulfate, polyethylene glycol octadecyl ether, and potassium palmitate. The mass ratio of the acrylic polymer monomer and the second emulsifier in the emulsion is 1:(0.3~1). The mass ratio of the acrylic polymer monomer and the second emulsifier in the emulsion may include, but is not limited to, 1:0.3, 1:0.32, 1:0.38, 1:0.4, 1:0.42, 1:0.8, 1:0.86, 1:0.9, or 1:1, or any two of the above values ​​as endpoints within a range.

[0124] In some examples, the molecular weight regulator includes one or more of tert-dodecyl mercaptan and n-octyl mercaptan. Exemplarily, the mass ratio of acrylic monomers to molecular weight regulators in the emulsion can be, but is not limited to, 1:(0.03~0.08). The mass ratio of acrylic monomers to molecular weight regulators in the emulsion can be, but is not limited to, 1:0.03, 1:0.04, 1:0.06, 1:0.07, or 1:0.08, or a range formed by any two of the above points as endpoints.

[0125] In some examples, the mass ratio of acrylic monomers to acrylate monomers in the emulsion is 1:(4~6). The mass ratio of acrylic monomers to acrylate monomers in the emulsion may include, but is not limited to, 1:4, 1:5, or 1:6, or any two of the above values ​​as endpoints.

[0126] In some of these examples, the emulsifier also includes an electrolytic aid. Further, the electrolytic aid may include, but is not limited to, one or more of potassium carbonate, potassium hydroxide, and potassium chloride.

[0127] In some examples, the second initiator includes one or more of potassium persulfate, tert-butanol peroxide, and azobisisobutyronitrile. Non-limitingly, the sum of the mass of the second initiator and the mass of the acrylic polymeric monomers included in the emulsion and monomer replenishment can be 1:(20-50). Exemplarily, the sum of the mass of the second initiator and the mass of the acrylic polymeric monomers included in the emulsion and monomer replenishment can be, but is not limited to, 1:20, 1:21, 1:22, 1:25, 1:48, or 1:50, or any two of the above values ​​as endpoints. It is understood that the second initiator may also be partially added to the monomer replenishment for initiation, provided that the total mass of the second initiator and the sum of the mass of the acrylic polymeric monomers included in the emulsion and monomer replenishment is 1:(20-50).

[0128] "Continuously adding monomer replenishment solution within a time interval of ≤4h" means adding monomer replenishment solution at a uniform rate within 4h. This facilitates the control of latex particle size in the polymer agglomerator latex, ensuring a stable and controllable monomer reaction rate and uniform latex particle growth.

[0129] In some examples, the mass ratio of acrylic monomers in the monomer replenishment solution to acrylate monomers in the monomer replenishment solution is 1:(2~5). Exemplarily, the mass ratio of acrylic monomers in the monomer replenishment solution to acrylate monomers in the monomer replenishment solution may include, but is not limited to, 1:2.2, 1:2.25, 1:2.5, 1:4.5, or 1:5, or any two of the above values ​​as endpoints within a range.

[0130] In some examples, the ratio of the sum of the mass of acrylic polymeric monomers included in the emulsion and monomer replenishment to the sum of the mass of acrylate polymeric monomers included in the emulsion and monomer replenishment is 1:(2~6). Understandably, this ratio is the same as the copolymerization mass ratio of acrylic polymeric monomers to acrylate polymeric monomers in the polymer agglomerator latex.

[0131] In some examples, the mass ratio of acrylic polymeric monomers included in the emulsion to the mass ratio of acrylic polymeric monomers included in the monomer replenishment liquid is 1:(0.5~4). Exemplarily, the mass ratio of acrylic polymeric monomers included in the emulsion to the mass ratio of acrylic polymeric monomers included in the monomer replenishment liquid may include, but is not limited to, 1:0.5, 1:0.6, 1:3, 1:3.5, 1:3.8, or 1:4, or any two of the above values ​​as endpoints within a range.

[0132] In some examples, the mass ratio of acrylate polymeric monomers included in the emulsion to the mass ratio of acrylate polymeric monomers included in the monomer replenishment liquid is 1:(0.4~2). Exemplarily, the mass ratio of acrylate polymeric monomers included in the emulsion to the mass ratio of acrylate polymeric monomers included in the monomer replenishment liquid may include, but is not limited to, 1:0.4, 1:0.42, 1:0.45, 1:0.5, 1:1.5, 1:1.8, or 1:2, or a range formed by any two of the above point values ​​as endpoints.

[0133] By adjusting the mass ratio of monomers in the emulsion and the monomer replenishment solution, within the above-mentioned ratio range, the monomers in the initial emulsion can first form stable micelles and initial latex particles. Subsequent addition of monomers in proportion can maintain a stable polymerization rate, preventing localized bursts and particle agglomeration due to excessive monomers, and avoiding low reaction efficiency and increased monomer residue due to insufficient addition. At the same time, it can gradually guide the uniform growth of latex particles and accurately control the particle size.

[0134] A third aspect of the present invention provides a sealant comprising styrene-butadiene latex of the first aspect of the present invention; or comprising styrene-butadiene latex prepared by any of the preparation methods of the second aspect of the present invention.

[0135] The styrene-butadiene latex of this invention combines the advantages of low viscosity and high solids content. When applied to styrene-butadiene latex systems, it maintains good fluidity even in high-solids-content systems, making it easy to blend with other base materials to form sealant products. Furthermore, the properties of styrene-butadiene latex reduce moisture evaporation, resulting in faster drying and curing of the formulated sealant, significantly improving production efficiency, rapidly forming a dense, continuous sealant film, and enhancing the cohesive strength and modulus of the cured sealant film.

[0136] The present invention will be further described in detail below with reference to some embodiments. It should also be understood that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of the present invention are within the scope of protection of the present invention. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the appropriate range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0137] Preparation Example 1

[0138] Preparation of the first styrene-butadiene latex A1: 1370g of water, 35g of potassium stearate (first emulsifier), 25g of potassium disproportionated rosinate (first emulsifier), 25g of potassium carbonate (salt additive), 8g of potassium hydroxide (pH adjuster), 750g of 1,3-butadiene, and 250g of styrene were added to a pressure vessel and stirred. The temperature inside the pressure vessel was controlled at 75℃. Then, 5g of potassium persulfate (first initiator) was added to initiate polymerization. The reaction was stopped when the monomer conversion rate was controlled at 99%. Unreacted monomers were removed by vacuum heating and the condensate was filtered off. The solid content of the first styrene-butadiene latex A1 was tested to be 45%, the Z-average particle size (average particle size) was 50nm, the pH value was 11, and the copolymer mass ratio of 1,3-butadiene to styrene in the first styrene-butadiene latex A1 was 3:1.

[0139] Preparation Example 2

[0140] Preparation of the first styrene-butadiene latex A2: 1974g of water, 20g of potassium stearate (first emulsifier), 15g of potassium disproportionated rosinate (first emulsifier), 15g of potassium carbonate (salt additive), 8g of potassium hydroxide (pH adjuster), 335g of 1,3-butadiene, and 670g of styrene were added to a pressure vessel and stirred. The temperature inside the pressure vessel was controlled at 75℃. Then, 5g of potassium persulfate (first initiator) was added to initiate polymerization. The reaction was stopped when the monomer conversion rate was controlled at 98%. Unreacted monomers were removed by vacuum heating and the condensate was filtered off. The solid content of the first styrene-butadiene latex A2 was tested to be 35%, the Z-average particle size was 75nm, the pH value was 10, and the mass ratio of 1,3-butadiene to styrene in the first styrene-butadiene latex A2 was 0.5:1.

[0141] Preparation Example 3

[0142] Preparation of the first styrene-butadiene latex A3: Add 2958g of water, 7g of potassium stearate (first emulsifier), 5g of potassium disproportionated rosinate (first emulsifier), 60g of potassium chloride (salt additive), 1g of potassium hydroxide (pH adjuster), 950g of 1,3-butadiene, and 50g of styrene into a pressure vessel and keep stirring. The temperature inside the pressure vessel was controlled at 75℃. Then, 2g of potassium persulfate (first initiator) was added to initiate polymerization. When the monomer conversion rate reached 25%, 3g of potassium disproportionated rosinate (first emulsifier), 2g of potassium persulfate (first initiator), and 100g of water were added. When the monomer conversion rate reached 50%, 5g of potassium palmitate (first emulsifier), 2g of potassium persulfate (first initiator), and 100g of water were added. The reaction was stopped when the monomer conversion rate reached 98%. Unreacted monomers were removed by vacuum heating. A 3% acetic acid aqueous solution was slowly added until the pH value reached 7.5. The condensate was filtered off. The solid content of the first styrene-butadiene latex A3 was tested to be 25%, the Z-average particle size was 150nm, and the copolymerization mass of butadiene and styrene in the first styrene-butadiene latex A3 was 19:1.

[0143] Preparation Example 4

[0144] Preparation of high molecular weight agglomerating agent latex B1: Add 5700g water, 30g sodium dodecyl sulfate (second emulsifier), 5g polyethylene glycol octadecyl ether (model: S10, second emulsifier), 5g potassium disproportionated rosinate (second emulsifier), 5g potassium stearate (second emulsifier), 5g potassium palmitate (second emulsifier), 1g tert-dodecyl mercaptan (molecular weight regulator), 3g n-octyl mercaptan (molecular weight regulator), 5g potassium chloride (electrolysis aid), 250g n-butyl acrylate, and 50g methacrylic acid to a pressure vessel and maintain stirring to prepare the mixture. The emulsion was prepared by controlling the temperature inside the pressure vessel at 75°C. 5g of potassium persulfate (second initiator) was added to initiate polymerization. Then, monomer replenishment solution (500g of n-butyl acrylate, 200g of methacrylic acid, 2g of potassium persulfate (second initiator), and 150g of water) was added at a uniform rate over 4 hours to carry out polymerization. The reaction was stopped when the monomer conversion rate reached 99.5%. Unreacted monomers were removed by vacuum heating. 3% acetic acid aqueous solution was slowly added until the pH value was 2. The coagulated material was filtered off. The solid content of the polymer agglomerating agent latex B1 was tested to be 15%, and the Z-average particle size was 70nm.

[0145] Preparation Example 5

[0146] Preparation of high molecular weight agglomerating agent latex B2: Add 3100g water, 25g sodium dodecyl sulfate (second emulsifier), 4g polyethylene glycol octadecyl ether (model: S10, second emulsifier), 4g potassium disproportionated rosinate (second emulsifier), 5g potassium stearate (second emulsifier), 5g potassium palmitate (second emulsifier), 2g tert-dodecyl mercaptan (molecular weight regulator), 1g n-octyl mercaptan (molecular weight regulator), 3g potassium chloride (electrolysis aid), 300g n-butyl acrylate, and 50g methacrylic acid to a pressure vessel and maintain... Stirring was used to prepare the emulsion. The temperature inside the pressure vessel was controlled at 75°C. 5g of potassium persulfate (second initiator) was added to initiate polymerization. Then, monomer replenishment solution (450g of n-butyl acrylate, 180g of methacrylic acid, and 20g of acrylic acid) was added at a uniform rate over 4 hours to carry out polymerization. The reaction was stopped when the monomer conversion rate reached 99.5%. Unreacted monomers were removed by vacuum heating. 3% potassium hydroxide aqueous solution was slowly added until the pH value was 5. The condensate was filtered off. The solid content of the polymer agglomerator latex B2 was tested to be 25%, and the Z-average particle size was 75nm.

[0147] Preparation Example 6

[0148] Preparation of latex B3 with polymer agglomerating agent: Add 1800g water, 16g sodium dodecyl sulfate (second emulsifier), 4g polyethylene glycol octadecyl ether (model: S10, second emulsifier), 2g potassium disproportionated rosinate (second emulsifier), 5g potassium stearate (second emulsifier), 5g potassium palmitate (second emulsifier), 2g tert-dodecyl mercaptan (molecular weight regulator), 1g n-octyl mercaptan (molecular weight regulator), 3g potassium chloride (electrolysis aid), 300g n-butyl acrylate, 300g isooctyl acrylate, and 100g methacrylic acid to a pressure vessel. While stirring, prepare the emulsion, control the temperature inside the pressure vessel at 75℃, add 5g of potassium persulfate (second initiator) to initiate polymerization, and then add monomer replenishment solution (250g of n-butyl acrylate, 50g of methacrylic acid, 2g of potassium persulfate, and 100g of water) at a uniform rate over 4 hours to carry out polymerization. Stop the reaction when the monomer conversion rate is controlled at 99.5%, remove unreacted monomers by vacuum heating, slowly add 3% potassium hydroxide aqueous solution until its pH value is 5.8, filter out the coagulated material, and test the solid content of the polymer agglomerator latex B3 to be 35% and the Z-average particle size to be 90nm.

[0149] Example 1

[0150] The first styrene-butadiene latex A1 has a pH value of 11, a solid content of 45%, an average particle size of 50 nm, and a copolymer mass ratio of butadiene to styrene of 3:1.

[0151] The polymer agglomerating agent latex B1 has a pH value of 2, an average particle size of 70 nm, a solid content of 15%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:3.

[0152] Polymer agglomerant latex B1 was added to the first styrene-butadiene latex A1. The mass ratio of the solid matter in the first styrene-butadiene latex A1 to the solid matter in the polymer agglomerant latex B1 was 100:0.3. The ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerant latex was 1:1.4. After mixing and expanding the particle size at 25°C for 60 min, the average Z-particle size of the expanded styrene-butadiene latex (C1) was 200 nm. Among them, latex particles with a particle size ≥250 nm accounted for 50% of the total latex particle volume, latex particles with a particle size ≤150 nm accounted for 10% of the total latex particle volume, and latex particles with a particle size >150 nm and <250 nm accounted for 40% of the volume. The styrene-butadiene latex C1 was further concentrated to a solid content of 67%, 68%, and 69%, respectively, with viscosities of 200 mPa·s, 270 mPa·s, and 410 mPa·s.

[0153] Example 2

[0154] The first styrene-butadiene latex A2 has a pH value of 10, a solid content of 35%, an average particle size of 75 nm, and a copolymer mass ratio of butadiene to styrene of 0.5:1.

[0155] The polymer agglomerating agent latex B2 has a pH value of 5, an average particle size of 75 nm, a solid content of 25%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:3.

[0156] Polymer agglomerant latex B2 was added to the first styrene-butadiene latex A2. The mass ratio of the solid matter in the first styrene-butadiene latex A2 to the solid matter in the polymer agglomerant latex B2 was 100:2. The ratio of the average particle size of the first styrene-butadiene latex A2 to the average particle size of the polymer agglomerant latex B2 was 1:1. After mixing and expanding at 25°C for 20 min, the Z-average particle size of the expanded styrene-butadiene latex (C2) was 271 nm. Among them, latex particles with a diameter ≥ 250 nm accounted for 60% of the total latex particle volume, latex particles with a diameter ≤ 150 nm accounted for 21% of the total latex particle volume, and latex particles with a diameter > 150 nm and a diameter < 250 nm accounted for 19% of the total latex particle volume. The particle size distribution diagram of the expanded styrene-butadiene latex C2 is shown in the figure below. Figure 1 As shown in the figure. The particle size distribution is obtained by diluting the expanded styrene-butadiene latex 40,000 times in pure water and then testing the particle size distribution using the Malvern Zetasizer Nano. The volume distribution of latex particles of different sizes can be directly read from the software.

[0157] Depend on Figure 1 It can be seen that the particle size distribution of styrene-butadiene latex C2 exhibits a bimodal distribution characteristic. In this embodiment, the particle size distribution diagram of styrene-butadiene latex shows a first peak and a second peak, and the peak particle sizes of the first and second peaks are shown in Table 1.

[0158] Styrene-butadiene latex C2 was concentrated to a solid content of 68%, 70%, and 72%, respectively, with viscosities of 230 mPa·s, 390 mPa·s, and 1090 mPa·s.

[0159] Example 3

[0160] The first styrene-butadiene latex A3 has a pH value of 7.5, a solid content of 25%, an average particle size of 150 nm, and a copolymer mass ratio of butadiene to styrene of 19:1.

[0161] The polymer agglomerating agent latex B3 has a pH value of 5.8, an average particle size of 90 nm, a solid content of 35%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:5.67.

[0162] Polymer agglomerant latex B3 was added to the first styrene-butadiene latex A3. The mass ratio of the solid matter in the first styrene-butadiene latex A3 to the solid matter in the polymer agglomerant latex B3 was 100:5. The ratio of the average particle size of the first styrene-butadiene latex A3 to the average particle size of the polymer agglomerant latex B3 was 1:0.6. After mixing and expanding at 45°C for 8 min, the Z-average particle size of the expanded styrene-butadiene latex (C3) was 500 nm. Among them, latex particles with a particle size ≥250 nm accounted for 70% of the total latex particle volume, latex particles with a particle size ≤150 nm accounted for 10% of the total latex particle volume, and latex particles with a particle size >150 nm and <250 nm accounted for 20% of the volume.

[0163] Styrene-butadiene latex C3 was concentrated to a solid content of 68%, 70%, and 72%, respectively, with viscosities of 210 mPa·s, 340 mPa·s, and 890 mPa·s.

[0164] Example 4

[0165] The first styrene-butadiene latex A2 has a pH value of 10, a solid content of 35%, an average particle size of 75 nm, and a copolymer mass ratio of butadiene to styrene of 0.5:1.

[0166] The polymer agglomerating agent latex B1 has a pH value of 2, an average particle size of 70 nm, a solid content of 15%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:3.

[0167] Polymer agglomerant latex B1 was added to the first styrene-butadiene rubber latex A2. The mass ratio of the solid matter in the first styrene-butadiene rubber latex A2 to the solid matter in the polymer agglomerant latex B1 was 100:1.8. The ratio of the average particle size of the first styrene-butadiene rubber latex A2 to the average particle size of the polymer agglomerant latex B1 was 1:0.93. After mixing and expanding at 25°C for 30 min, the Z-average particle size of the expanded styrene-butadiene rubber latex (C4) was 277 nm. Among them, latex particles with a diameter ≥250 nm accounted for 60% of the total latex particle volume, latex particles with a diameter ≤150 nm accounted for 31% of the total latex particle volume, and latex particles with a diameter >150 nm and a diameter <250 nm accounted for 9% of the total latex particle volume. The particle size distribution diagram of the expanded styrene-butadiene rubber latex C4 is shown in the figure. Figure 2 As shown. By Figure 2It can be seen that the particle size distribution of styrene-butadiene latex C4 exhibits a three-peak distribution characteristic. In this embodiment, the particle size distribution diagram of styrene-butadiene latex shows a first peak and a second peak, and the peak particle sizes of the first and second peaks are shown in Table 1.

[0168] Styrene-butadiene latex C4 was concentrated to a solid content of 67%, 68%, and 69%, respectively, with viscosities of 180 mPa·s, 240 mPa·s, and 390 mPa·s.

[0169] Example 5

[0170] Water was slowly added to polymer agglomerant latex B1 and mixed until its solid content was 12% to obtain polymer agglomerant latex B5.

[0171] Polymer agglomerant latex B5 was added to the first styrene-butadiene rubber latex A1. The mass ratio of the solid matter in the first styrene-butadiene rubber latex A1 to the solid matter in the polymer agglomerant latex B5 was 100:0.3. The ratio of the average particle size of the first styrene-butadiene rubber latex to the average particle size of the polymer agglomerant latex was 1:1.4. After mixing and expanding the particle size at 25°C for 10 min, the Z-average particle size of the expanded styrene-butadiene rubber latex (C5) was 180 nm. Among them, latex particles with a particle size ≥250 nm accounted for 41% of the total latex particle volume, latex particles with a particle size ≤150 nm accounted for 23% of the total latex particle volume, and latex particles with a particle size >150 nm and <250 nm accounted for 36% of the total latex particle volume. The styrene-butadiene rubber latex C5 was further concentrated until the solid content was 67% and its viscosity was 2700 mPa·s.

[0172] Example 6

[0173] The first styrene-butadiene latex A3 has a pH value of 7.5, a solid content of 25%, an average particle size of 150 nm, and a copolymer mass ratio of butadiene to styrene of 19:1.

[0174] The polymer agglomerating agent latex B3 has a pH value of 5.8, an average particle size of 90 nm, a solid content of 35%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:5.67.

[0175] Polymer agglomerant latex B3 was added to the first styrene-butadiene rubber latex A3. The mass ratio of the solid matter in the first styrene-butadiene rubber latex A3 to the solid matter in the polymer agglomerant latex B3 was 100:3. The ratio of the average particle size of the first styrene-butadiene rubber latex A3 to the average particle size of the polymer agglomerant latex B3 was 1:0.6. After mixing and expanding the particle size at 15°C for 360 min, the Z-average particle size of the expanded styrene-butadiene rubber latex (C6) was 230 nm. Among them, latex particles with a particle size ≥250 nm accounted for 55% of the total latex particle volume, latex particles with a particle size ≤150 nm accounted for 38% of the total latex particle volume, and latex particles with a particle size >150 nm and <250 nm accounted for 7%. The particle size distribution diagram of the expanded styrene-butadiene rubber latex C6 is shown in the figure. Figure 3 As shown. By Figure 3 It can be seen that the particle size distribution of styrene-butadiene latex C6 exhibits a bimodal distribution characteristic. In this embodiment, the particle size distribution diagram of styrene-butadiene latex shows a first peak and a second peak, and the peak particle sizes of the first and second peaks are shown in Table 1. When styrene-butadiene latex C6 was concentrated to a solid content of 67%, 68%, and 69%, its viscosities were 390 mPa·s, 490 mPa·s, and 680 mPa·s, respectively.

[0176] Comparative Example 1

[0177] Comparative Example 1 used Styrene-butadiene latex A1, which was not expanded by a polymer agglomerator. When the concentrated solids content was 55%, the Styrene-butadiene latex was found to be completely paste-like. Before concentration, the average particle size of the first Styrene-butadiene latex A1 was 50 nm, of which latex particles with a diameter ≥250 nm accounted for 0% of the total latex particle volume, and latex particles with a diameter ≤150 nm accounted for 100% of the total latex particle volume.

[0178] Comparative Example 2

[0179] The first styrene-butadiene latex A3 has a pH value of 7.5, a solid content of 25%, an average particle size of 150 nm, and a copolymer mass ratio of butadiene to styrene of 19:1.

[0180] The polymer agglomerating agent latex B3 has a pH value of 5.8, an average particle size of 90 nm, a solid content of 35%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:5.67.

[0181] Polymer agglomerant latex B3 was added to the first styrene-butadiene latex A3. The mass ratio of the solid matter in the first styrene-butadiene latex A3 to the solid matter in the polymer agglomerant latex B3 was 100:6.5. The ratio of the average particle size of the first styrene-butadiene latex A3 to the average particle size of the polymer agglomerant latex B3 was 1:0.6. After mixing and expanding at 45°C for 8 min, the average particle size of the expanded styrene-butadiene latex (C7) Z- was 510 nm, of which latex particles with a particle size ≥250 nm accounted for 87% of the total latex particle volume, and latex particles with a particle size ≤150 nm accounted for 0% of the total latex particle volume.

[0182] When styrene-butadiene latex C7 is concentrated to a solid content of 67%, its viscosity is 3500 mPa·s.

[0183] Comparative Example 3

[0184] The first styrene-butadiene latex A3 has a pH value of 7.5, a solid content of 25%, an average particle size of 150 nm, and a copolymer mass ratio of butadiene to styrene of 19:1.

[0185] The polymer agglomerating agent latex B1 has a pH value of 2, an average particle size of 70 nm, a solid content of 15%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:3.

[0186] Polymer agglomerant latex B1 was added to the first styrene-butadiene latex A3, with a mass ratio of solids in the first styrene-butadiene latex A3 to solids in the polymer agglomerant latex B1 of 100:5; the average particle size ratio of the first styrene-butadiene latex to the polymer agglomerant latex was 1:0.47; after mixing and expanding at 25°C for 30 min, the Z-average particle size of the expanded styrene-butadiene latex (C8) was 330 nm, of which latex particles with a diameter ≥250 nm accounted for 80% of the total latex particle volume, and latex particles with a diameter ≤150 nm accounted for 5% of the total latex particle volume. The styrene-butadiene latex C8 was further concentrated to a solid content of 67% and a viscosity of 3800 mPa·s.

[0187] Comparative Example 4

[0188] The first styrene-butadiene latex A1 has a pH value of 11, a solid content of 45%, an average particle size of 50 nm, and a copolymer mass ratio of butadiene to styrene of 3:1.

[0189] The polymer agglomerating agent latex B2 has a pH value of 5, an average particle size of 75 nm, a solid content of 25%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:3.

[0190] Polymer agglomerant latex B2 was added to the first styrene-butadiene latex A1, with a mass ratio of solid matter in the first styrene-butadiene latex A1 to solid matter in the polymer agglomerant latex B2 of 100:0.3; the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerant latex was 1:1.5; after mixing and expanding at 25°C for 10 min, the Z-average particle size of the expanded styrene-butadiene latex (C9) was 195 nm, of which latex particles with a particle size ≥250 nm accounted for 40% of the total latex particle volume, and latex particles with a particle size ≤150 nm accounted for 20% of the total latex particle volume. The styrene-butadiene latex C9 was further concentrated until the solid content was 67%, and its viscosity was 3100 mPa·s.

[0191] Comparative Example 5

[0192] The first styrene-butadiene latex A1 has a pH value of 11, a solid content of 45%, an average particle size of 50 nm, and a copolymer mass ratio of butadiene to styrene of 3:1.

[0193] Alkali conditioning was used to modify latex B1, which was pretreated by slowly adding a 5% potassium hydroxide aqueous solution to latex B1 and mixing until the pH value reached 7.3, resulting in modified latex B4. First styrene-butadiene latex A1 was then added to the modified latex B4, with a solids-to-solids ratio of 100:0.3. The average particle size ratio of the first styrene-butadiene latex to the polymeric agglomerator latex was 1:1.4. After mixing and expanding at 25°C for 10 min, the Z-average particle size of the expanded styrene-butadiene latex (C10) was 66 nm, with latex particles ≥250 nm accounting for 0% of the total latex particle volume and particles ≤150 nm accounting for 100% of the total latex particle volume. The particle size distribution diagram of C10 styrene-butadiene latex particles after expansion is shown in the figure below. Figure 4 As shown. Further concentration of styrene-butadiene latex C10 was carried out until the solid content was 56%, and it was found that the styrene-butadiene latex had been completely paste-like.

[0194] Comparative Example 6

[0195] The polymer agglomerating agent latex B3 has a pH value of 5.8, an average particle size of 90 nm, a solid content of 35%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:5.67.

[0196] A modified styrene-butadiene latex A3 was pretreated using an acid-adjusting process to obtain modified styrene-butadiene latex A4. The modified styrene-butadiene latex A4 was prepared by adding a 5% (w / w) aqueous acetic acid solution to styrene-butadiene latex A3 to adjust the pH of the latex to 7.3. The modified styrene-butadiene latex A4 had the following characteristics: pH 7.3, solid content 25%, average particle size 150 nm, and a copolymer mass ratio of butadiene to styrene of 19:1.

[0197] Modified styrene-butadiene latex A4 was added to polymer agglomerator latex B3. The mass ratio of the solids in modified styrene-butadiene latex A4 to the solids in polymer agglomerator latex B3 was 100:5. The average particle size ratio of modified styrene-butadiene latex A4 to the average particle size of polymer agglomerator latex B3 was 1:0.6. After mixing and expanding the particle size at 45°C for 8 minutes, the latex was found to have formed a paste.

[0198] Comparative Example 7

[0199] The first styrene-butadiene latex A2 has a pH value of 10, a solid content of 35%, an average particle size of 75 nm, and a copolymer mass ratio of butadiene to styrene of 0.5:1.

[0200] Preparation of high-molecular-weight agglomerating agent latex B5: Add 5700g water, 8g sodium dodecyl sulfate (second emulsifier), 3g polyethylene glycol octadecyl ether (model: S10, second emulsifier), 2g potassium disproportionated rosinate (second emulsifier), 5g potassium stearate (second emulsifier), 5g potassium palmitate (second emulsifier), 1g tert-dodecyl mercaptan (molecular weight regulator), 3g n-octyl mercaptan (molecular weight regulator), 5g potassium chloride (electrolysis aid), 500g n-butyl acrylate, and 150g methacrylic acid to a pressure vessel and maintain stirring to prepare the emulsion. The liquid was prepared by controlling the temperature inside the pressure vessel at 75°C. 5g of potassium persulfate (second initiator) was added to initiate polymerization. Then, monomer replenishment solution (250g of n-butyl acrylate, 100g of methacrylic acid, 2g of potassium persulfate (second initiator), and 150g of water) was added at a uniform rate over 4 hours to carry out polymerization. The reaction was stopped when the monomer conversion rate reached 99.5%. Unreacted monomers were removed by vacuum heating. 3% acetic acid aqueous solution was slowly added until the pH value was 2. The condensate was filtered off, and the solid content of the polymer agglomerator latex B5 was tested to be 15%, and the Z-average particle size was 120nm.

[0201] The polymer agglomerating agent latex B5 has a pH value of 2, an average particle size of 120 nm, a solid content of 15%, and a copolymerization mass ratio of acrylic polymer monomers to acrylate polymer monomers of 1:3.

[0202] Polymer agglomerant latex B5 was added to the first styrene-butadiene latex A2. The mass ratio of the solid matter in the first styrene-butadiene latex A2 to the solid matter in the polymer agglomerant latex B5 was 100:1.8. The ratio of the average particle size of the first styrene-butadiene latex A2 to the average particle size of the polymer agglomerant latex B5 was 1:1.6. After mixing and expanding the particle size at 25°C for 30 min, the average particle size of the expanded styrene-butadiene latex (C11) Z- was 205 nm. Among them, latex particles with a particle size ≥250 nm accounted for 39% of the total latex particle volume, latex particles with a particle size ≤150 nm accounted for 57% of the total latex particle volume, and latex particles with a particle size >150 nm and <250 nm accounted for 4% of the volume.

[0203] When styrene-butadiene latex C11 is concentrated to a solid content of 67%, its viscosity is 3800 mPa·s.

[0204] The parameters used in the preparation of styrene-butadiene latex in the above embodiments and comparative examples are shown in Tables 1 and 2.

[0205] Table 1

[0206]

[0207] Table 2

[0208]

[0209] As can be seen from the above examples, the styrene-butadiene latex prepared in the embodiments of the present invention can have a lower viscosity at a higher solid content compared to the styrene-butadiene latex of the comparative example. Comparative Example 1 only used the first styrene-butadiene latex to prepare the styrene-butadiene latex. At this time, the average particle size of the styrene-butadiene latex was low, and the volume ratio of large latex particles with a particle size ≥250nm was insufficient, resulting in paste formation at a solid content of 55%.

[0210] In Comparative Example 2, the mass ratio of solids in the first styrene-butadiene latex to solids in the polymer agglomerator latex exceeded 100:(0.3~0.5). The unreasonable mass ratio of the two led to an excessively vigorous agglomeration reaction of the styrene-butadiene latex. As a result, the average particle size of the styrene-butadiene latex was high, and the volume ratio of small latex particles with a particle size ≤150nm was insufficient. Consequently, the styrene-butadiene latex could not simultaneously possess the advantages of high solids content and low viscosity.

[0211] In Comparative Example 3, the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerator latex was less than 1:(0.6~1.4). Under these conditions, the volume ratio of small latex particles with a particle size ≤150nm in the obtained styrene-butadiene latex was insufficient, which led to an increase in viscosity of the styrene-butadiene latex under high solids content conditions.

[0212] In Comparative Example 4, the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerator latex was higher than 1:(0.6~1.4). Under these conditions, the volume ratio of large-diameter rubber particles with a particle size ≥250nm in the styrene-butadiene latex was insufficient, which also affected the viscosity of the styrene-butadiene latex under high solids content conditions.

[0213] Comparative Example 5 uses an alkali-modifying process to modify and pretreat the polymer agglomerator latex to obtain modified polymer agglomerator latex B4. First styrene-butadiene latex A1 is added to the modified polymer agglomerator latex B4. At this time, the steps of alkali-modifying the polymer agglomerator latex pretreatment and adding the first styrene-butadiene latex to the modified polymer agglomerator latex will affect the agglomeration process of styrene-butadiene latex. The volume ratio of small-diameter rubber particles with a particle size ≤150nm is too high, which leads to the paste phenomenon of styrene-butadiene latex during the concentration process.

[0214] Comparative Example 6 uses an acid-modifying process to modify the first styrene-butadiene latex to obtain modified first styrene-butadiene latex A4. Modified first styrene-butadiene latex A4 is added to the polymer agglomerating agent latex B3. At this time, the steps of modifying the first styrene-butadiene latex with acid and adding modified first styrene-butadiene latex A4 to the polymer agglomerating agent latex B3 will lead to a decrease in the stability of latex particles and the latex particles are prone to agglomeration. After mixing and expanding the diameter at 25°C for 10 minutes, it was found that the latex had solidified.

[0215] In Comparative Example 7, the polymer agglomerator latex B5 has a large particle size, with an average particle size exceeding the range of 60nm to 90nm. This leads to an increase in the average particle size of the styrene-butadiene latex after expansion, and the volume ratio of large-diameter particles with a particle size ≥250nm is insufficient, which in turn affects the achievement of low viscosity of styrene-butadiene latex.

[0216] In addition, compared with Examples 1 to 6, the solid content of the polymer agglomerating agent latex in Examples 1 to 4 and Examples 6 is 15% to 35%. This solid content increases the agglomeration probability between latex particles, and the volume ratio of large-diameter latex particles with a particle size ≥250nm is 50% to 70%, which is beneficial to reducing the viscosity of styrene-butadiene latex.

[0217] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0218] The above-described embodiments are merely illustrative of several implementation methods of the present invention, facilitating a detailed understanding of the technical solutions of the present invention, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided by the present invention through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims of the present invention.

Claims

1. A styrene-butadiene latex, characterized in that, The average particle size of the styrene-butadiene latex is 180nm~500nm; The volume percentage of latex particles with a particle size ≥250nm in the styrene-butadiene latex is 41%~70%, the volume percentage of latex particles with a particle size ≤150nm in the styrene-butadiene latex is 10%~38%, and the volume percentage of latex particles with a particle size >150nm and a particle size <250nm in the styrene-butadiene latex is 7%~42%. The solid content of the styrene-butadiene latex is ≥67%, and the viscosity of the styrene-butadiene latex at 25°C is ≤2700mPa·s.

2. The styrene-butadiene latex according to claim 1, characterized in that, The average particle size of the styrene-butadiene latex is 200nm~500nm, the volume percentage of latex particles with a particle size ≥250nm in the styrene-butadiene latex is 50%~70%, the solid content of the styrene-butadiene latex is 67%~72%, and the viscosity of the styrene-butadiene latex at 25℃ is 180mPa·s~1100mPa·s.

3. The styrene-butadiene latex according to claim 1 or 2, characterized in that, The particle size distribution of the styrene-butadiene latex has bimodal or multimodal characteristics. Optionally, the particle size distribution of the styrene-butadiene latex has a first peak and a second peak, the peak particle size of the first peak is 40nm~110nm, and the peak particle size of the second peak is 250nm~960nm.

4. A method for preparing styrene-butadiene latex, characterized in that, Includes the following steps: A second styrene-butadiene latex is prepared by adding a polymer agglomerating agent to the first styrene-butadiene latex, followed by mixing, diameter expansion, and concentration. Wherein, the ratio of the average particle size of the first styrene-butadiene latex to the average particle size of the polymer agglomerating agent latex is 1:(0.6~1.4); the average particle size of the polymer agglomerating agent latex is 60nm~90nm; The mass ratio of the solids in the first styrene-butadiene latex to the solids in the polymer agglomerating agent latex is 100:(0.3~5); The average particle size of the second styrene-butadiene rubber latex is 180nm~500nm; the volume percentage of latex particles with a particle size ≥250nm in the second styrene-butadiene rubber latex is 41%~70%, the volume percentage of latex particles with a particle size ≤150nm in the second styrene-butadiene rubber latex is 10%~38%, the volume percentage of latex particles with a particle size >150nm and <250nm in the second styrene-butadiene rubber latex is 7%~42%, the solid content of the second styrene-butadiene rubber latex is ≥67%, and the viscosity of the second styrene-butadiene rubber latex at 25℃ is ≤2700mPa·s.

5. The method for preparing styrene-butadiene latex according to claim 4, characterized in that, The first styrene-butadiene latex has a solid content of 25% to 45%, and the polymer agglomerating agent latex has a solid content of 15% to 35%. The average particle size of the styrene-butadiene latex is 200nm~500nm, the volume percentage of latex particles with a particle size ≥250nm in the second styrene-butadiene latex is 50%~70%, the solid content of the second styrene-butadiene latex is 67%~72%, and the viscosity of the second styrene-butadiene latex at 25℃ is 180mPa·s~1100mPa·s.

6. The method for preparing styrene-butadiene latex according to claim 4 or 5, characterized in that, The pH value of the first styrene-butadiene latex is 7.5~11; and / or, The latex containing the polymer agglomerating agent has a pH value of 2 to 5.9; and / or, The mixing and expansion temperature is 10℃~45℃, and the mixing and expansion time is 8min~360min; and / or, The average particle size of the first styrene-butadiene latex is 50 nm to 150 nm; and / or, The copolymer mass ratio of butadiene to styrene in the first styrene-butadiene latex is (0.5~19):

1.

7. The method for preparing styrene-butadiene latex according to claim 4 or 5, characterized in that, The preparation steps of the first styrene-butadiene latex include: Butadiene, styrene, a first emulsifier, a first initiator and a first dispersion medium are mixed and subjected to a first polymerization reaction to prepare the first styrene-butadiene latex; Optionally, the temperature for carrying out the first polymerization reaction is 70°C to 80°C; Optionally, the mass ratio of butadiene to styrene is (0.5~19):1; Optionally, the mass ratio of styrene to the first emulsifier is 1:(0.05~0.3); Optionally, the mass ratio of styrene to the first initiator is 1:(0.005~0.15); Optionally, the first emulsifier includes one or more of potassium stearate, potassium disproportionated rosinate, sodium dodecyl sulfate, polyethylene glycol octadecyl ether, and potassium palmitate; Optionally, the first initiator includes one or more of potassium persulfate, tert-butanol peroxide, and azobisisobutyronitrile; Optionally, the first dispersion medium includes water.

8. The method for preparing styrene-butadiene latex according to claim 4 or 5, characterized in that, The polymeric agglomerating agent latex is a copolymer containing carboxylic acid groups, and the copolymer includes acrylic polymeric monomers and acrylate polymeric monomers; Optionally, the acrylic polymeric monomer includes one or more of methacrylic acid and acrylic acid; Optionally, the acrylate polymeric monomers include one or more of n-butyl acrylate and isooctyl acrylate; Optionally, the copolymerization mass ratio of the acrylic polymer monomer and the acrylate polymer monomer is 1:(2~6).

9. The method for preparing styrene-butadiene latex according to claim 8, characterized in that, The preparation steps of the polymer agglomerating agent latex include: After heating the emulsion, a second initiator is added, and then monomer replenishment liquid is continuously added within a time interval of ≤4 hours to carry out the second polymerization reaction and prepare the polymer agglomerator latex. The emulsion includes a second dispersion medium, a second emulsifier, a molecular weight regulator, acrylic polymer monomers, and acrylate polymer monomers. The monomer replenishment solution includes acrylic polymer monomers and acrylate polymer monomers; Optionally, the second dispersion medium includes water; Optionally, the second emulsifier includes one or more of potassium stearate, potassium disproportionated rosinate, sodium dodecyl sulfate, polyethylene glycol octadecyl ether, and potassium palmitate; Optionally, the molecular weight regulator includes one or more of tert-dodecyl mercaptan and n-octyl mercaptan; Optionally, the second initiator includes one or more of potassium persulfate, tert-butanol peroxide, and azobisisobutyronitrile; Optionally, the ratio of the sum of the mass of the acrylic polymer monomers included in the emulsion and the monomer replenishment liquid to the sum of the mass of the acrylate polymer monomers included in the emulsion and the monomer replenishment liquid is 1:(2~6). Optionally, the mass ratio of the acrylic polymer monomer included in the emulsion to the mass of the acrylic polymer monomer included in the monomer replenishment liquid is 1:(0.5~4); Optionally, the mass ratio of the acrylate polymer monomers included in the emulsion to the mass of the acrylate polymer monomers included in the monomer replenishment liquid is 1:(0.4~2). Optionally, the mass ratio of the acrylic polymer monomer to the second emulsifier in the emulsion is 1:(0.3~1); Optionally, the mass ratio of the acrylic polymer monomer to the molecular weight regulator in the emulsion is 1:(0.03~0.08); Optionally, the mass ratio of the acrylic polymer monomers in the emulsion to the acrylate polymer monomers in the emulsion is 1:(4~6); Optionally, the mass ratio of the acrylic polymer monomer in the monomer replenishment solution to the acrylate polymer monomer in the monomer replenishment solution is 1:(2~5).

10. A sealant, characterized in that, Includes the styrene-butadiene latex according to any one of claims 1 to 3; or includes the styrene-butadiene latex prepared by any one of claims 4 to 9.

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