Preparation method of high-stability modified styrene-butadiene latex

Abstract

The invention relates to the technical field of high polymer materials, and discloses a preparation method of high-stability modified styrene-butadiene latex. The method comprises the following steps: finely selecting raw materials, for example, controlling the contents of monomers such as butadiene (40-60%), styrene (30-50%) and functional monomers (1-10%) according to the mass percent, adopting initiators such as potassium persulfate (0.1-1% of the weight of the monomers), compounding anionic and nonionic emulsifiers, and preparing the high-strength and high-toughness polyurethane elastomer. And adding an organic silicon modifier (0.5-3% of the weight of the monomer) and nano particles (0.1-2% of the weight of the monomer), and carrying out pre-emulsification, polymerization reaction, modification treatment, post-treatment and the like. The prepared modified styrene-butadiene latex has high chemical, mechanical and storage stability and excellent cohesiveness and film-forming property, the preparation raw materials are environment-friendly, the process is simple and controllable, and the application prospect is wide.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a method for preparing highly stable modified styrene-butadiene latex. Background Art

[0002] Styrene butadiene latex is a polymer emulsion made by emulsion polymerization with butadiene and styrene as the main monomers. Due to its good adhesion, film-forming properties and mechanical stability, it is widely used in papermaking, textiles, construction, coatings and other fields. However, traditional styrene butadiene latex has certain defects in stability. For example, under high temperature, high shear force or long-term storage conditions, it is easy to cause demulsification and flocculation, resulting in a decrease in latex performance, limiting its application in some special working conditions and high-end fields. With the continuous improvement of material performance requirements in various industries, it is of great practical significance to develop a modified styrene butadiene latex with high stability and its preparation method. Summary of the invention

[0003] The present invention provides a method for preparing a highly stable modified styrene-butadiene latex, comprising the following steps:

[0004] According to mass fraction, 40%-60% butadiene, 30%-50% styrene, and 1%-10% functional monomer are prepared as monomer raw materials;

[0005] Use water-soluble initiators such as potassium persulfate or ammonium persulfate, and the amount used is 0.1%-1% of the total monomer amount;

[0006] A compound emulsifier is used, including anionic emulsifier and nonionic emulsifier, wherein the amount of anionic emulsifier is 1%-3% of the total monomer amount, and the amount of nonionic emulsifier is 0.5%-2% of the total monomer amount;

[0007] Anionic emulsifiers include sodium dodecylbenzene sulfonate or sodium dodecyl sulfate; nonionic emulsifiers include Tween-80, phenethylphenol polyoxypropylene polyoxyethylene ether, benzylphenol polyoxyethylene ether or fatty alcohol polyoxyethylene ether.

[0008] Prepare an organosilicon modifier such as vinyl triethoxysilane, γ-aminopropyl triethoxysilane, etc. in an amount of 0.5% to 3% of the total monomer amount, and nanoparticles such as nano silicon dioxide, nano calcium carbonate, etc. in an amount of 0.1% to 2% of the total monomer amount;

[0009] Add an appropriate amount of sodium bicarbonate as a buffer to adjust the pH value of the reaction system to between 7 and 9;

[0010] Pre-emulsification is carried out. Deionized water, emulsifier, buffer and part of monomers are added into a pre-emulsification kettle with a stirring device. The stirring speed is controlled at 200-500r / min, the temperature is maintained at 20-30°C, the pre-emulsification time is 30-60min, and a pre-emulsification solution is formed. The deionized water is 2-3 times the total mass of the monomers.

[0011] The pre-emulsion is transferred to a polymerization reaction kettle equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction device. After nitrogen is introduced to replace the air, the temperature is raised to 60-80°C, and an initiator aqueous solution is added to initiate the polymerization reaction. During the reaction, the remaining monomers and the initiator aqueous solution are added dropwise, and the reaction temperature is controlled at 70-80°C. The reaction time is 4-8 hours until the monomer conversion rate reaches more than 95%; the concentration of the initiator aqueous solution is 5%-8%.

[0012] In the late stage of the polymerization reaction, when the monomer conversion rate reaches about 90%, add the pre-dispersed organosilicon modifier and nanoparticles, continue stirring the reaction for 1-2 hours, the stirring speed is 300-600r / min, and the temperature is maintained at 70-80℃;

[0013] After the polymerization reaction is completed, the reaction product is cooled to room temperature, and an appropriate amount of pH regulator is added to adjust the pH value of the latex to 7-8. Then, impurities and unreacted particles in the latex are removed by filtration or centrifugation to obtain a highly stable modified styrene-butadiene latex.

[0014] Furthermore, the functional monomer is one or more of acrylic acid and methyl methacrylate.

[0015] Furthermore, in the pre-emulsification step, the amount of the added part of the monomers accounts for 30%-60% of the total amount of the monomers.

[0016] Furthermore, during the polymerization reaction, the rate of adding the remaining monomers and the initiator aqueous solution is 2-4 drops / s.

[0017] Furthermore, the organosilicon modifier is dispersed by ultrasonic dispersion or high-speed stirring before being added into the reaction kettle.

[0018] Furthermore, before adding the nanoparticles into the reactor, the particle sizes of the nanoparticles are uniformly distributed by ultrasonic dispersion or ball milling.

[0019] Furthermore, the pH adjuster is dilute hydrochloric acid or dilute sodium hydroxide solution.

[0020] Furthermore, the highly stable modified styrene butadiene latex prepared by the method is characterized in that the modified styrene butadiene latex does not show demulsification or flocculation after being heated at 80° C. for 30 minutes, stirred at a high speed of 10,000 r / min for 30 minutes, and stored at room temperature for 6 months.

[0021] Furthermore, the modified styrene butadiene latex is coated on paper, and after drying and forming a film, the tensile strength of the paper is increased by 20%-30% compared with the paper coated with traditional styrene butadiene latex; when coated on fabric, the peel strength of the fabric is increased by 30%-50% compared with the fabric coated with traditional styrene butadiene latex.

[0022] Furthermore, the tensile strength of the film formed by the modified styrene-butadiene latex is 15%-25% higher than that of the traditional styrene-butadiene latex film, and the elongation at break is 10%-20% higher. After being immersed in water for 72 hours, the weight increase rate of the film is less than 5%.

[0023] Beneficial technical effects:

[0024] High stability: The chemical stability, mechanical stability and storage stability of styrene-butadiene latex have been significantly improved by compounding emulsifiers, introducing modifiers and nanoparticles, and optimizing the preparation process. After being treated at high temperature (80°C) and high shear force (10,000 r / min) for 30 minutes, and stored at room temperature for 6 months, the modified styrene-butadiene latex did not show demulsification or flocculation, while the traditional styrene-butadiene latex showed a significant decrease in stability.

[0025] Excellent bonding performance: The introduction of functional monomers and the effect of organosilicon modifiers enable the modified styrene butadiene latex to form stronger chemical bonds and physical adsorption when in contact with various substrates (such as paper, fabric, wood, etc.), thereby improving the bonding strength of the latex. In paper coating applications, the tensile strength of paper coated with modified styrene butadiene latex is increased by 20%-30%, and the peel strength is increased by 30%-50%.

[0026] Good film-forming properties: The film formed by modified styrene-butadiene latex has better uniformity, flexibility and water resistance. The tensile strength of the film is increased by 15%-25%, and the elongation at break is increased by 10%-20%. After soaking in water for 72 hours, the weight increase rate of the film is less than 5%, while the weight increase rate of traditional styrene-butadiene latex film is more than 10%.

[0027] Environmental performance: The raw materials and additives selected in the present invention meet environmental protection requirements, do not produce harmful substances in the preparation process, reduce pollution to the environment, and meet the requirements of sustainable development. DETAILED DESCRIPTION

[0028] Example 1

[0029] Raw materials preparation:

[0030] Monomer raw materials: by mass fraction, prepare 45% butadiene, 45% styrene, and 10% acrylic acid (as a functional monomer).

[0031] Initiator: Potassium persulfate is used as a water-soluble initiator, and its dosage is 0.1% of the total monomer. In the polymerization reaction, the dosage of the initiator has an important influence on the start and rate of the reaction. The setting of the lower limit value helps to observe the reaction of the system at a lower initiator concentration.

[0032] Emulsifier: A compound emulsifier is used, in which the amount of anionic emulsifier sodium dodecylbenzene sulfonate is 1% of the total monomer amount, and the amount of nonionic emulsifier Tween-80 is 0.5% of the total monomer amount. Emulsifiers are crucial to forming a stable emulsion system. The use of the lower limit value can explore the effect of emulsifiers on emulsion stability at the lowest effective dosage.

[0033] Modifier and nanoparticles: Prepare 0.5% of the total monomer amount of vinyl triethoxysilane as an organosilicon modifier and 0.1% of the total monomer amount of nano-silicon dioxide as nanoparticles. Organosilicon modifiers and nanoparticles can improve the performance of latex, and the setting of the lower limit value can study the minimum contribution of the performance improvement.

[0034] Buffer: Add an appropriate amount of sodium bicarbonate as a buffer and adjust the pH value of the reaction system to 7. The appropriate pH value plays an important role in the stability of the polymerization reaction and the performance of the product. The lower limit pH = 7 can determine the feasibility of the method under relatively low alkaline conditions.

[0035] Pre-emulsification:

[0036] In a pre-emulsification kettle with a stirring device, add deionized water (deionized water is twice the total weight of the monomer), emulsifier, buffer and monomer accounting for 30% of the total monomer. Deionized water is used as a reaction medium, and its dosage affects the concentration and dispersion effect of the system. The setting of the lower limit can study the pre-emulsification effect under a relatively concentrated system.

[0037] The stirring speed was controlled at 200 r / min, the temperature was maintained at 20°C, and the pre-emulsification time was 30 minutes to form a pre-emulsion. The lower stirring speed, temperature, and shorter pre-emulsification time represent the lower limit conditions of the pre-emulsification process, and the pre-emulsification effect of this method under such mild conditions can be examined.

[0038] Polymerization reaction:

[0039] The pre-emulsion was transferred to a polymerization reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet device, and the temperature was raised to 60° C. After nitrogen was introduced to replace the air, the nitrogen was replaced to create an oxygen-free environment to avoid the interference of oxygen on the polymerization reaction. The starting temperature of 60° C. is the lower limit of the polymerization reaction temperature range.

[0040] The polymerization reaction was initiated by adding an initiator aqueous solution with a concentration of 5%. During the reaction, the initiator aqueous solution and the remaining monomers were added dropwise at a rate of 2 drops / s, and the reaction temperature was controlled at 70°C. The lower initiator concentration and dropwise rate, as well as the lower limit of the reaction temperature of 70°C, are helpful for observing the progress and results of the polymerization reaction under relatively mild conditions.

[0041] The reaction time is 4 h, until the monomer conversion rate reaches more than 95%. The short reaction time lower limit can verify the ability of this method to achieve high monomer conversion rate in the shortest time.

[0042] Post-processing:

[0043] At the end of the polymerization reaction, when the monomer conversion rate reaches about 90%, the organosilicon modifier pre-dispersed by ultrasound (ultrasonic power 200W, time 10min) and the nanoparticles whose particle size is uniformly distributed by ultrasound dispersion (ultrasonic power 200W, time 15min) are added, and the stirring reaction is continued for 1h. The stirring speed is 300r / min and the temperature is maintained at 70°C. The operating conditions at this stage are also the lower limits of various parameters, and the effects of modifiers and nanoparticles on the performance of the final product under such conditions can be studied.

[0044] After the polymerization reaction is completed, the reaction product is cooled to room temperature, diluted hydrochloric acid is added as a pH regulator to adjust the pH value of the latex to 7, and then the impurities and unreacted particles in the latex are removed by filtering to obtain a highly stable modified styrene-butadiene latex.

[0045] Example 2

[0046] Raw materials preparation:

[0047] Monomer raw materials: by mass fraction, prepare 50% butadiene, 40% styrene, and 10% methyl methacrylate (as a functional monomer).

[0048] Initiator: Ammonium persulfate was selected as a water-soluble initiator, and its dosage was 1% of the total monomer amount. A higher dosage of initiator may accelerate the reaction rate, and the polymerization reaction at the upper limit value was examined.

[0049] Emulsifier: A compound emulsifier is used, in which the amount of anionic emulsifier sodium dodecylbenzene sulfonate is 3% of the total monomer amount, and the amount of nonionic emulsifier Tween-80 is 2% of the total monomer amount. A higher amount of emulsifier may enhance the stability of the emulsion, and the effect of the upper limit on the stability of the emulsion is studied.

[0050] Modifier and nanoparticles: γ-aminopropyltriethoxysilane was prepared as a silicone modifier at a dosage of 3% of the total monomer, and nanoparticles were used at a dosage of 2% of the total monomer. The higher the dosage of modifier and nanoparticles, the greater the degree of improvement in latex performance can be explored.

[0051] Buffer: Add an appropriate amount of sodium bicarbonate as a buffer to adjust the pH of the reaction system to 9. A higher upper limit of pH can be used to study the feasibility of the reaction and product performance under relatively high alkaline conditions.

[0052] Pre-emulsification:

[0053] In a pre-emulsification kettle with a stirring device, deionized water (deionized water is 3 times the total weight of the monomer), emulsifier, buffer and 60% of the total monomer are added. A larger amount of deionized water and a higher proportion of monomers can be added to study the pre-emulsification effect in a relatively dilute system.

[0054] The stirring speed was controlled at 500r / min, the temperature was maintained at 30°C, and the pre-emulsification time was 60min to form a pre-emulsion. Higher stirring speed, temperature and longer pre-emulsification time represent the upper limit conditions of the pre-emulsification process, and the pre-emulsification effect of this method under such more severe conditions can be examined.

[0055] Polymerization reaction:

[0056] The pre-emulsion was transferred to a polymerization reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet device, and the temperature was raised to 80° C. The starting temperature of 80° C. is the upper limit of the polymerization temperature range, and the characteristics of the polymerization reaction at a higher temperature can be observed.

[0057] An 8% aqueous initiator solution was added to initiate the polymerization reaction. During the reaction, the aqueous initiator solution and the remaining monomers were added dropwise at a rate of 4 drops / s, and the reaction temperature was controlled at 80° C. The higher initiator concentration and dropwise rate, as well as the upper limit of the reaction temperature of 80° C., are helpful in observing the progress and results of the polymerization reaction under more intense conditions.

[0058] The reaction time is 8 hours, until the monomer conversion rate reaches more than 95%. The longer upper limit of the reaction time can verify the performance of the product of the method under the longest time.

[0059] Post-processing:

[0060] At the end of the polymerization reaction, when the monomer conversion rate reaches about 90%, the organic silicon modifier dispersed in advance by high-speed stirring (speed 10000r / min, time 30min) and the nanoparticles whose particle size is uniformly distributed by ball milling (ball milling time 4h) are added, and the stirring reaction is continued for 2h. The stirring speed is 600r / min and the temperature is maintained at 80℃. The upper limit values ​​of each parameter at this stage can be used to study the effects of modifiers and nanoparticles on the performance of the final product under such harsh conditions.

[0061] After the polymerization reaction is completed, the reaction product is cooled to room temperature, and a dilute sodium hydroxide solution is added as a pH regulator to adjust the pH value of the latex to 8. Then, impurities and unreacted particles in the latex are removed by centrifugation to obtain a highly stable modified styrene-butadiene latex.

[0062] Comparative Example 1

[0063] Raw materials preparation:

[0064] Monomer raw materials: by mass fraction, 50% of butadiene, 40% of styrene and 10% of acrylic acid are taken as monomer raw materials.

[0065] Initiator: Potassium persulfate was selected as a water-soluble initiator, and the amount used was 0.5% of the total monomer amount.

[0066] Emulsifier: In the compound emulsifier, the amount of anionic emulsifier sodium dodecylbenzene sulfonate is 2% of the total monomer amount, and the amount of nonionic emulsifier Tween-80 is 1% of the total monomer amount.

[0067] No addition of silicone modifiers and nanoparticles: The purpose is to compare the effects of adding modifiers and nanoparticles on product performance.

[0068] Buffer: Add appropriate amount of sodium bicarbonate as a buffer to adjust the pH value of the reaction system to 8.

[0069] Pre-emulsification:

[0070] Deionized water (the amount of deionized water is 2.5 times the total weight of the monomers), an emulsifier, a buffer and monomers accounting for 50% of the total weight of the monomers are added into a pre-emulsification kettle equipped with a stirring device.

[0071] The stirring speed was controlled at 300 r / min, the temperature was maintained at 25°C, and the pre-emulsification time was 45 min to form a pre-emulsion.

[0072] Polymerization reaction:

[0073] The pre-emulsion was transferred to a polymerization reactor equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen inlet device. After nitrogen was introduced to replace the air, the temperature was raised to 70°C.

[0074] An initiator aqueous solution with a concentration of 6% was added to initiate the polymerization reaction. During the reaction, the initiator aqueous solution and the remaining monomers were added dropwise at a rate of 3 drops / s, and the reaction temperature was controlled at 75°C.

[0075] The reaction time is 6 h, until the monomer conversion rate reaches more than 95%.

[0076] Post-processing:

[0077] After the polymerization reaction is completed, the reaction product is cooled to room temperature, a dilute sodium hydroxide solution is added to adjust the pH value of the latex to 7.5, and then the impurities and unreacted particles in the latex are removed by filtering to obtain ordinary styrene-butadiene latex.

[0078] (V) Test results

[0079] Table 1 Comparison of synergy

[0080]

[0081]

[0082] It can be clearly seen from the table data that the modified styrene butadiene latex prepared in Example 1 and Example 2 is significantly superior to the ordinary styrene butadiene latex of Comparative Example 1 in terms of stability and various application properties. This fully demonstrates that according to the method described in the claims, by reasonably selecting the dosage range of each component, the preparation of highly stable and high-performance modified styrene butadiene latex has a significant synergistic effect.

[0083] The invention provides a method for preparing a highly stable modified styrene butadiene latex, which successfully prepares a modified styrene butadiene latex with high stability, excellent bonding performance and film-forming performance by carefully selecting raw materials, optimizing the preparation process and introducing effective modification means. The preparation method has the advantages of simple process, strong operability and controllable cost, and the prepared modified styrene butadiene latex has broad application prospects in the fields of papermaking, textiles, construction, etc., and is expected to bring new development opportunities to related industries.

Claims

1. A method for preparing a highly stable modified styrene-butadiene latex, characterized in that: The following steps are involved: According to mass fraction, 40%-60% butadiene, 30%-50% styrene, and 1%-10% functional monomer are prepared as monomer raw materials; Use potassium persulfate or ammonium persulfate water-soluble initiator, the dosage of which is 0.1%-1% of the total monomer amount; A compound emulsifier is used, including anionic emulsifier and nonionic emulsifier, wherein the amount of anionic emulsifier is 1%-3% of the total monomer amount, and the amount of nonionic emulsifier is 0.5%-2% of the total monomer amount; Prepare an organosilicon modifier such as vinyl triethoxysilane and γ-aminopropyl triethoxysilane in an amount of 0.5% to 3% of the total monomer amount, and nanoparticles in an amount of 0.1% to 2% of the total monomer amount; Add an appropriate amount of sodium bicarbonate as a buffer to adjust the pH value of the reaction system to between 7 and 9; Pre-emulsification is carried out. Deionized water, emulsifier, buffer and part of monomers are added into a pre-emulsification kettle with a stirring device. The stirring speed is controlled at 200-500r / min, the temperature is maintained at 20-30°C, the pre-emulsification time is 30-60min, and a pre-emulsification solution is formed. The deionized water is 2-3 times the total mass of the monomers. The pre-emulsion is transferred to a polymerization reaction kettle equipped with a stirrer, a thermometer, a reflux condenser and a nitrogen introduction device, and after nitrogen is introduced to replace the air, the temperature is raised to 60-80°C, and an initiator aqueous solution is added to initiate the polymerization reaction. During the reaction, the initiator aqueous solution and the remaining monomers are added dropwise, and the reaction temperature is controlled at 70-80°C. The reaction time is 4-8 hours until the monomer conversion rate reaches more than 95%, and the concentration of the initiator aqueous solution is 5%-8%; In the late stage of the polymerization reaction, when the monomer conversion rate reaches about 90%, add the pre-dispersed organosilicon modifier and nanoparticles, continue stirring the reaction for 1-2 hours, the stirring speed is 300-600r / min, and the temperature is maintained at 70-80℃; After the polymerization reaction is completed, the reaction product is cooled to room temperature, and an appropriate amount of pH regulator is added to adjust the pH value of the latex to 7-8. Then, impurities and unreacted particles in the latex are removed by filtration or centrifugation to obtain a highly stable modified styrene-butadiene latex.

2. The method for preparing a highly stable modified styrene-butadiene latex according to claim 1, wherein: The functional monomer is one or more of acrylic acid and methyl methacrylate.

3. The method for preparing a highly stable modified styrene-butadiene latex according to claim 1, characterized in that: In the pre-emulsification step, the amount of added partial monomers accounts for 30%-60% of the total amount of monomers.

4. The method for preparing a highly stable modified styrene-butadiene latex according to claim 1, wherein: During the polymerization reaction, the remaining monomers and the initiator aqueous solution are added dropwise at a rate of 2-4 drops / s.

5. The method for preparing a highly stable modified styrene-butadiene latex according to claim 1, characterized in that: The organosilicon modifier is dispersed by ultrasonic dispersion or high-speed stirring before being added into the reaction kettle.

6. The method for preparing a highly stable modified styrene-butadiene latex according to claim 1, characterized in that: Before adding the nanoparticles into the reactor, the particle sizes of the nanoparticles are uniformly distributed by ultrasonic dispersion or ball milling.

7. The method for preparing a highly stable modified styrene-butadiene latex according to claim 1, characterized in that: The pH regulator is dilute hydrochloric acid or dilute sodium hydroxide solution.

8. A highly stable modified styrene-butadiene latex prepared by the method according to any one of claims 1 to 7, characterized in that: The modified styrene-butadiene latex does not show demulsification or flocculation after being heated at 80° C. for 30 minutes, stirred at a high speed of 10,000 r / min for 30 minutes, and stored at room temperature for 6 months.

9. The highly stable modified styrene-butadiene latex according to claim 8, characterized in that: The modified styrene butadiene latex is coated on paper and dried to form a film, and the tensile strength of the paper is increased by 20%-30% compared with the paper coated with traditional styrene butadiene latex; and the peeling strength of the fabric is increased by 30%-50% compared with the fabric coated with traditional styrene butadiene latex.

10. The highly stable modified styrene-butadiene latex according to claim 8, characterized in that: The tensile strength of the film formed by the modified styrene-butadiene latex is 15%-25% higher than that of the traditional styrene-butadiene latex film, and the elongation at break is 10%-20% higher. After being immersed in water for 72 hours, the weight increase rate of the film is less than 5%.

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