A kind of compound viscosity reducer is used for the method for one-step synthesis of high solid content styrene-butadiene rubber latex

Abstract

The application belongs to the field of high polymer materials, and particularly relates to a method for synthesizing high solid content styrene-butadiene latex by one-step method using a compounded viscosity reducer, and the compounded viscosity reducer comprises a small molecule inorganic salt containing potassium ions and a polyether amine, wherein the weight ratio of the small molecule inorganic salt containing potassium ions to the polyether amine is 5-100:1. The small molecule inorganic salt containing potassium ions and the polyether amine are used as the compounded viscosity reducer, and the styrene-butadiene latex with a solid content of more than 60% can be synthesized by one-step method. The method solves the problem of excessive system viscosity in the process of synthesizing high solid latex by one-step method, reduces the subsequent concentration step, reduces the complexity of the reaction, reduces energy consumption, and saves cost.

Description

Technical Field

[0001] This invention belongs to the field of high-polymer materials, specifically relating to a method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer. Background Technology

[0002] Styrene-butadiene latex is a type of latex prepared by emulsion polymerization of butadiene and styrene. Due to its good adhesion, stability and flowability, it is widely used in roads, adhesives, waterproofing, ABS grafting, carpets, construction, coatings, foaming materials, papermaking and other fields.

[0003] Using high-solids-content styrene-butadiene rubber (SBR) latex as a modifier to modify emulsified asphalt can significantly improve the asphalt's resistance to high and low temperatures. Viscosity control is crucial during the preparation of high-solids-content SBR latex. Latex particle size and distribution are the main factors determining the relationship between solids content and viscosity. Viscosity reducers are indispensable additives in the synthesis of high-solids-content latex, playing a role in controlling the system's viscosity and latex rheology during the reaction. At the same solids content, larger particle size results in lower viscosity; conversely, in latex with the same particle size, higher solids content leads to higher viscosity. The solids content of SBR latex is a deep-seated factor affecting viscosity, closely related to the hydration layer of latex particles. On one hand, a large amount of water is fixed on the latex particles in the form of a hydration layer, reducing the amount of free water in the system and resulting in higher viscosity. On the other hand, the volume of latex particles increases many times due to the presence of the hydration layer, increasing the resistance to particle movement during latex flow and thus increasing viscosity.

[0004] Currently, the main production methods for high-solids-content styrene-butadiene rubber (SBR) latex are the "one-step method" and the "two-step method." The "one-step method" increases the proportion of monomers and various additives in the synthesis formula by reducing the water content, directly producing high-solids-content SBR latex through high-temperature or low-temperature emulsion polymerization. The "two-step method" uses a specific polymerization process to first prepare SBR latex with a specific particle size distribution, then uses physical or chemical agglomeration methods to prepare larger-particle-size SBR latex, and finally concentrates the latex to remove water and increase the solids content, producing a high-solids-content SBR latex with suitable viscosity. The high-solids-content SBR latex produced by the "one-step method" is pure and has excellent properties. However, during the synthesis process, the viscosity of the reaction system increases with the increase of solids content, which is detrimental to material dispersion and temperature control in the later stages of polymerization, easily leading to uneven dispersion, gelation, and reduced latex stability. Therefore, the requirements for formulation design, polymerization process, and reaction equipment are more stringent when preparing high-solids-content SBR latex using the "one-step method." The high-solids-content styrene-butadiene latex product prepared by the "two-step method" is relatively pure and has good performance, and the production process is easy to control. However, the styrene-butadiene latex synthesized from the base latex in the first step has a low solids content due to insufficient monomer conversion, which reduces the production efficiency of the equipment and increases the cost of the degassing and concentration processes. In addition, the agglomeration process is relatively complex, and the agglomeration process directly affects the stability and agglomeration effect of the styrene-butadiene latex, thus affecting the stability and solids content of the high-solids-content styrene-butadiene latex. Summary of the Invention

[0005] To address the existing technical problems, this invention provides a method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer. The method employs a small-molecule inorganic salt containing potassium ions and polyetheramine as the compound viscosity reducer, enabling the synthesis of styrene-butadiene latex with a solids content of over 60% in a single step. This solves the problem of excessively high system viscosity in the one-step synthesis of high-solids latex; it also reduces subsequent concentration steps, simplifies the reaction process, lowers energy consumption, and saves costs.

[0006] In traditional techniques, the viscosity-reducing effect of a single viscosity reducer significantly limits the viscosity of the latex, resulting in limited viscosity changes during use. Once a certain solids content is reached, the viscosity change cannot be effectively and continuously controlled, thus limiting further increases in the latex solids content. This can lead to a paste-like state or even demulsification, affecting the latex's application performance. To address the problems of single viscosity reducers and the technical difficulties in traditional high-solids-content styrene-butadiene latex preparation, this invention proposes a compound viscosity reducer containing a small-molecule inorganic salt with potassium ions and a polyetheramine.

[0007] The inventors discovered through long-term research that the solid content of polymer emulsions is the underlying cause affecting viscosity, and is closely related to the hydration layer of latex particles. On the one hand, because a large amount of water is fixed on the latex particles in the form of a hydration layer, the amount of free water in the system is reduced; on the other hand, the volume of latex particles increases many times due to the presence of the hydration layer, which increases the resistance to particle movement during latex flow. Therefore, hydration results in reduced fluidity and increased viscosity of the emulsion system. If the thickness of the hydration layer on the surface of latex particles can be reduced without compromising the stability of the latex, or if the total surface area of ​​the latex particles can be reduced (for example, by aggregating small particles into larger particles, thus reducing the total surface area), the water content in the hydration layer can be reduced, thereby lowering the viscosity of the emulsion. Based on the above findings, the inventors propose a composite viscosity reducer. Potassium ions have a high degree of binding to water in the system, which can absorb bound water around latex particles, releasing the bound water around the latex particles and increasing the free water in the system, thereby reducing the viscosity of the latex. Secondly, in emulsion polymerization, the addition of an appropriate amount of electrolyte can inhibit gelation and promote the initial reaction rate. This helps to increase the latex particle size and improve the flowability and stability of the latex. The viscosity-reducing mechanism of polyetheramine agglomeration conforms to the steric hindrance mechanism, also known as the steric effect or entropy effect. The steric hindrance mechanism mainly applies to polymer dispersants, and their superior performance depends on the unique anchoring groups and solvation chains in their structure. Common solvation chains include (polyether, polyester, polyolefin, and polyacrylate), etc. In a polarity-matched medium, the solvation chains extend into the dispersion medium (i.e., the particles), causing the polymers on adjacent particles to repel each other due to the volume effect, effectively maintaining the suspension stability of the system, thereby reducing the viscosity of the system while maintaining the stability of the latex.

[0008] Small-molecule inorganic salts containing potassium ions and polyetheramines, as inorganic viscosity reducers suitable for high-solids styrene-butadiene latex systems, can reduce the thickness of the hydration layer around latex particles, thereby reducing the volume of latex particles and increasing the release capacity of bound water from latex particles, thus achieving the effect of reducing system viscosity. Polyetheramines, as a high-molecular-weight agglomerating agent, can cause latex particles to aggregate during the synthesis of high-solids styrene-butadiene latex, increasing the latex particle size and releasing bound water, thus achieving the purpose of reducing system viscosity. The composite viscosity reducer of this invention, through the effective combination of two different viscosity reducer methods, and by adjusting the usage ratio and feeding process of the two viscosity reducers during use, successfully solves the problems of excessive viscosity during the synthesis of high-solids-content latex in the "one-step" method, which limits the increase in solid content, results in low conversion rate, and causes glue and wall adhesion to the reactor and agitator, while not affecting the stability of the latex.

[0009] The addition method of compound viscosity reducers: During initial feeding, a portion of small-molecule inorganic salts containing potassium ions is added to the system. This ensures latex stability while simultaneously reducing system viscosity. When the reaction reaches a conversion rate of 40-45%, the remaining small-molecule inorganic salts containing potassium ions are added to the system. This reduces the critical micelle concentration of the emulsifier, increases the polymerization rate, and provides a sustained effect, further reducing system viscosity. When the reaction reaches a conversion rate of 60-70%, polyetheramine is added to the system. This increases the latex particle size and also reduces system viscosity. For the "one-step" synthesis of high-solids-content latex, in addition to using compound viscosity reducers during initial feeding, a certain amount of viscosity reducer is added to the system at 40-45% and 60-70% to reduce system viscosity, increase system fluidity, improve the reaction rate, increase monomer conversion while increasing solids content, and reduce material loss and the pressure caused by subsequent monomer release.

[0010] The specific technical solution of the present invention is as follows:

[0011] A method for one-step synthesis of high solids content styrene-butadiene latex using a compound viscosity reducer, comprising a small molecule inorganic salt containing potassium ions and a polyetheramine, wherein the weight ratio of potassium chloride to polyetheramine is 5-100:1.

[0012] Preferably, the average molecular weight of the polyetheramine is 2000-3000. Polyetheramine is a high molecular weight agglomerant with a molecular weight range of 2000-3000. At this molecular weight, the polymer exhibits steric hindrance, causing the polymers on adjacent particles to repel each other due to volume effects, effectively maintaining the suspension stability of the system and promoting particle size growth and stability.

[0013] Preferably, the small molecule inorganic salt containing potassium ions is one or more of potassium chloride, potassium sulfate, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate.

[0014] Preferably, the specific steps are as follows: emulsifier, reducing agent, dispersant, stabilizer, molecular weight regulator, some small molecule inorganic salts containing potassium ions, and polymerizing monomers are added to the polymerization reactor in the order of aqueous phase first and oil phase second. The temperature is raised to the polymerization temperature of 45-55℃, and an initiator is added to initiate the polymerization reaction. When the reaction reaches a conversion rate of 40-45%, the remaining small molecule inorganic salts containing potassium ions are added to the system. When the reaction reaches a conversion rate of 60%-70%, polyetheramine is added to the system. When the solid content is above 60%, the reaction is complete.

[0015] Addition method of compound viscosity reducer: For the "one-step" synthesis of high solid content latex, in addition to using compound viscosity reducer in the initial feeding, a certain amount of viscosity reducer should be added to the system when the solid content reaches 40-45% and 60-70% to reduce the viscosity of the system, increase the fluidity of the system, improve the reaction rate, increase the conversion rate of monomers while increasing the solid content, and reduce the material loss and the pressure caused by subsequent monomer release.

[0016] More preferably, the polymerizable monomers are butadiene and styrene in a weight ratio of 7-7.5:2.5-3.

[0017] More preferably, the polymerization reaction material comprises, by weight percentage of the polymerizing monomers, 3.0-6.0% emulsifier, 0.2-0.4% initiator, 0.5-1% dispersant, 0.05-0.21% molecular weight regulator, 0.2-0.6% reducing agent, and 0.2-5% stabilizer. That is, the weight of the above material can be obtained by multiplying the weight of the polymerizing monomers by the above weight percentages.

[0018] More preferably, the weight ratio of the small molecule inorganic salt containing potassium ions to the remaining small molecule inorganic salt containing potassium ions is 1:0 to 2:1.

[0019] More preferably, the emulsifier is one or more of potassium oleate, potassium disproportionated rosinate, sodium stearate, and sodium dodecylbenzene sulfonate; the initiator is an organic hydrogen peroxide compound; the dispersant is one or more of disodium methylene bis(naphthalene sulfonate), methylene bis(4-toluene sulfonate), and naphthalene sulfonate formaldehyde condensate; the molecular weight regulator is an alkyl thiol organic compound; and the reducing agent is a ferrous salt, or one or more of sodium thiosulfate, pyrophosphate, sodium EDTA, sodium dithionite, and sodium sulfide.

[0020] More preferably, the initiator is one or more of dichloropropylbenzene peroxide, di-tert-butylpropylbenzene peroxide, triisopropylbenzene peroxide, chloropropylbenzene peroxide, and hydroperoxide-p-menthane, and the molecular weight regulator is one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan, and tert-tetradecyl mercaptan.

[0021] More preferably, the stabilizer is one or two of dodecylamine polyoxyethylene ether, octadecylamine polyoxyethylene ether, and alkylphenol polyoxyethylene ether.

[0022] Compared to the traditional one-step method, this invention effectively solves the problem of excessive viscosity in the synthesis of high-solids latex. Compared to the traditional two-step method, the one-step synthesis of high-solids latex in this invention reduces subsequent concentration steps, simplifies the reaction process, reduces energy consumption, and saves costs. This invention provides a method for the one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer. By using two viscosity reducers in combination, the viscosity of the system is effectively reduced, the latex concentration step is reduced, the reaction time is shortened, the reaction efficiency is improved, and energy consumption and material loss are reduced. It has the advantages of simple process, low cost, convenience, and low pollution. Detailed Implementation

[0023] The following detailed embodiments further illustrate the above-described content of the present invention, but should not be construed as limiting the scope of the subject matter of the present invention to the following examples. All technologies implemented based on the above-described content of the present invention fall within the scope of the present invention. Unless otherwise specified, the following embodiments are all implemented using conventional prior art.

[0024] The specific polyetheramines in the following examples and comparative examples are: bifunctional primary amines with repeating oxypropylene units on the main chain, the amino groups are located on secondary carbon atoms at the end of the aliphatic polyether chain, and the average molecular weight is 2000. The specific structure is as follows:

[0025]

[0026] Example 1

[0027] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0028] Potassium oleate (3.0g), disodium methylene bis(naphthalene) sulfonate (1g), sodium dithionite (0.5g), dodecylamine polyoxyethylene ether (0.4g), n-dodecyl mercaptan (0.08g), KCl (0.66g), water (80g), styrene (30g), and butadiene (70g) were added sequentially to the polymerization reactor. The temperature was raised to the polymerization temperature of 50℃, and dichloroisopropylbenzene hydrogen peroxide (0.2g) was added to initiate the polymerization reaction. When the conversion rate reached 40%, 0.33g of potassium chloride was added to continue the polymerization reaction. When the conversion rate reached 60%, polyetheramine (0.1g) was added to the system, and the solid content was above 60%. The polymerization reaction was then stopped, and the reaction was completed.

[0029] Example 2

[0030] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0031] Sodium dodecylbenzenesulfonate (3.0g), methylene bis(4-toluenesulfonate) (1g), sodium dithionite (0.5g), octadecylamine polyoxyethylene ether (0.4g), tert-dodecyl mercaptan (0.08g), KCl (1g), water (80g), styrene (30g), and butadiene (70g) were added sequentially to the polymerization reactor. The temperature was raised to the polymerization temperature of 50℃, and di-tert-butylisopropylbenzene hydrogen peroxide (0.2g) was added to initiate the polymerization reaction. When the conversion rate reached 60%, a certain amount of polyetheramine (0.1g) was added to the system to make the solid content above 60%, and the polymerization reaction was stopped. The reaction was then complete.

[0032] Example 3

[0033] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0034] Potassium disproportionated rosinate (3.0g), naphthalene sulfonate formaldehyde condensate (1g), sodium dithionite (0.5g), alkylphenol polyoxyethylene ether (0.4g), tetradecyl mercaptan (0.08g), KCl (0.33g), water (80g), styrene (30g), and butadiene (70g) were added sequentially to the polymerization reactor. The temperature was raised to the polymerization temperature of 50℃, and triisopropylbenzene hydrogen peroxide (0.2g) was added to initiate the polymerization reaction. When the conversion rate reached 40%, 0.66g of potassium chloride was added to continue the polymerization reaction. When the conversion rate reached 60%, the viscosity of the system was measured, and a certain amount of polyetheramine (0.1g) was added to the system. When the solid content was above 60%, the polymerization reaction was stopped, and the reaction was completed.

[0035] Comparative Example 1

[0036] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0037] Potassium oleate (3g), disodium methylene bis(naphthalene)sulfonate (1g), sodium dithionite (0.5g), dodecylamine polyoxyethylene ether (0.4g), n-dodecyl mercaptan (0.08g), water (80g), styrene (30g), and butadiene (70g) were added sequentially to the polymerization reactor, following the order of aqueous phase first, then oil phase. The temperature was raised to the polymerization temperature of 50°C, and dichloropropylbenzene hydrogen peroxide (0.2g) was added to initiate the polymerization reaction. When the conversion rate reached 40%, 1g of potassium chloride was added, and the polymerization reaction was continued. When the conversion rate reached 60%, polyetheramine (0.1g) was added to the system, and the solid content was above 60%. The polymerization reaction was then stopped, and the reaction was complete.

[0038] Comparative Example 2

[0039] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0040] The only difference from Comparative Example 1 is that the amount of potassium chloride and polyetheramine added to the polymerization reactor is 0; everything else is the same as Comparative Example 1.

[0041] Comparative Example 3

[0042] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0043] The only difference from Comparative Example 1 is that the amount of potassium chloride added to the reactor is 0, and the amount of polyetheramine added is 0.1g, which are the same as Comparative Example 1.

[0044] Comparative Example 4

[0045] A method for one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer:

[0046] The only difference from Example 1 is that the amount of polyetheramine added to the reactor is 0; otherwise, it is the same as Example 1.

[0047] test

[0048] When the reaction reaches a conversion rate of 40%, the latex viscosity is measured (recorded as viscosity 1). When the reaction reaches a conversion rate of 60%, the system viscosity is measured (recorded as viscosity 2). Once the target solid content is reached, the reaction is stopped, and the final latex viscosity is recorded (recorded as viscosity 3). The effect of the viscosity reducer on the system is evaluated by the changes in viscosity during the process sampling, latex indices (mechanical stability, surface tension), and application performance. Application performance test: Asphalt: Qilu 70#, soap solution: imidazoline cationic emulsifier, by weight, 60 parts asphalt, 2 parts soap solution, 38 parts water, ground in a colloid mill for 2 minutes, the dry rubber accounts for 2.5% of the asphalt mass, the sample is steamed, and then the softening point and ductility are tested.

[0049] The specific tests are shown in Table 1:

[0050] Table 1 Data Table

[0051]

[0052] As can be seen from the viscosity change trend in Table 1, the use of a compound viscosity reducer with a specific and appropriate dosage ratio in the examples can effectively reduce the viscosity of the system. The reduction in viscosity has a significant effect on increasing the solid content of the latex. At the same time, the mechanical stability and surface tension of the latex were tested. The results show that the use of a compound viscosity reducer with a specific and appropriate dosage ratio has little impact on the mechanical stability of the latex, and the change in surface tension is not significantly different. In the application of modified emulsified asphalt, the softening point and ductility of the examples both reached the target values. The use of the compound viscosity reducer of the present invention does not affect the subsequent application process.

[0053] Compared to the traditional one-step method, this invention effectively solves the problem of excessive viscosity in the synthesis of high-solids latex. Compared to the traditional two-step method, the one-step synthesis of high-solids latex in this invention reduces subsequent concentration steps, simplifies the reaction process, reduces energy consumption, and saves costs. This invention provides a method for the one-step synthesis of high-solids-content styrene-butadiene latex using a compound viscosity reducer. By using two viscosity reducers in combination, the viscosity of the system is effectively reduced, the latex concentration step is reduced, the reaction time is shortened, the reaction efficiency is improved, and energy consumption and material loss are reduced. It has the advantages of simple process, low cost, convenience, and low pollution.

[0054] The viscosity changes described above indicate that the use of compound viscosity reducers can effectively lower the viscosity during the synthesis of high-solids latex without affecting its stability. Furthermore, the use of compound viscosity reducers has a minimal impact on the stability and application performance of high-solids latex. Therefore, the use of compound viscosity reducers makes it possible to implement the traditional one-step synthesis of high-solids styrene-butadiene latex, which is of great significance for material conservation and energy reduction, and provides possibilities for subsequent engineering transformation and continuous production.

Claims

1. A process for one step synthesis of high solid content styrene butadiene latex using a compounded viscosity reducing agent, characterized in that, The complex viscosity reducer comprises a small-molecule inorganic salt containing potassium ions and a polyether amine, wherein the weight ratio of the small-molecule inorganic salt containing potassium ions to the polyether amine is 5-100:1; The average molecular weight of the polyether amine is 2000-3000; The small-molecule inorganic salt containing potassium ions is one or more of potassium chloride, potassium sulfate, potassium dihydrogen phosphate and dipotassium hydrogen phosphate; The specific steps are as follows: (1) The emulsifier, reducing agent, diffusing agent, stabilizer, molecular weight regulator, part of potassium chloride, and polymerization monomer are sequentially added into a polymerization reactor in the order of water phase first and oil phase later, the temperature is raised to a polymerization temperature of 45-55°C, an initiator is added to initiate polymerization, when the conversion rate reaches 40-45%, the remaining potassium chloride is added into the system, when the conversion rate reaches 60-70%, the polyether amine is added into the system, and the reaction is completed when the solid content is above 60%; The weight ratio of the part of potassium chloride to the remaining potassium chloride is 1:0-2:

1.

2. A process for one step synthesis of high solid content styrene butadiene latex using a compounded viscosity reducing agent as claimed in claim 1, wherein, The use amount of the complex viscosity reducer is 0.51-1.1% of the weight of the polymerization monomer.

3. A process for one step synthesis of high solid content styrene butadiene latex using a compounded viscosity reducing agent as claimed in claim 1, wherein, The emulsifier is 3.0-6.0%, the initiator is 0.2-0.4%, the diffusing agent is 0.5-1%, the molecular weight regulator is 0.05-0.21%, the reducing agent is 0.2-0.6%, and the stabilizer is 0.2-5% of the weight percentage of the polymerization monomer.

4. A process for one step synthesis of high solid content styrene butadiene latex using a compounded viscosity reducing agent as claimed in claim 1, wherein, The polymerization monomer is butadiene and styrene, and the weight ratio is 7-7.5:2.5-3.

5. A process for one step synthesis of high solid content styrene butadiene latex using a compounded viscosity reducing agent as claimed in claim 1, wherein, The emulsifier is one or more of potassium oleate, potassium disulfated rosin acid, sodium stearate and sodium dodecyl benzene sulfonate; the initiator is an organic peroxide compound; the diffusing agent is one or more of methylene bis naphthalene sulfonate disodium salt, methylene bis (4-toluene sulfonate) and naphthalene sulfonate formaldehyde condensate; the molecular weight regulator is an alkyl mercaptan organic compound; the reducing agent is one or more of divalent iron salt, white lead, pyrophosphate, sodium EDTA, sodium hyposulfite and sodium sulfide; and the stabilizer is one or more of dodecyl amine polyoxyethylene ether, octadecyl amine polyoxyethylene ether and alkyl phenol polyoxyethylene ether.

6. A process for one step synthesis of high solid content styrene butadiene latex using a compounded viscosity reducing agent as claimed in claim 5, wherein, The initiator is one or more of chloro diisopropyl benzene peroxide, di-tert-butyl isopropyl benzene peroxide, triisopropyl benzene peroxide, chloro isopropyl benzene peroxide and p-menthane peroxide, and the molecular weight regulator is one or more of n-dodecyl mercaptan, tert-dodecyl mercaptan and tert-tetradecyl mercaptan.

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