Preparation method of degradable carboxylic butadiene-styrene latex

Abstract

The invention relates to the field of high polymer materials, in particular to a preparation method of degradable carboxylic butadiene-styrene latex. A degradable cyclic monomer, a bio-based monomer and a degradable cross-linking agent are introduced; in the method, a plurality of innovative processes such as step-by-step emulsion polymerization, supercritical carbon dioxide assistance, enzymatic and chemical polymerization synergy and the like are adopted. The prepared latex has good degradability, and can balance the original properties such as cohesiveness and film-forming property.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer materials, and particularly relates to a preparation method of degradable carboxylated styrene-butadiene latex. Background Art

[0002] Carboxylated styrene-butadiene latex is a polymer emulsion obtained by introducing carboxyl functional groups through emulsion polymerization using butadiene and styrene as the main monomers. It has advantages such as good adhesiveness and film-forming property, and has been widely used in many industrial fields. However, with the increasingly strict environmental regulations and the emphasis on sustainable development, the environmental defects of existing carboxylated styrene-butadiene latex have gradually emerged, mainly reflected in the following aspects:

[0003] Environmental pollution caused by non-degradability: Traditional carboxylated styrene-butadiene latex is mainly composed of polymer chains connected by carbon-carbon covalent bonds, which are difficult to be decomposed by microorganisms in the natural environment. Long-term existence in the environment such as soil and water will cause serious white pollution and pose a threat to the balance of the ecosystem and biodiversity.

[0004] Unsustainability of raw materials: Most of the monomers such as butadiene and styrene used in its production process are derived from petrochemical products. The limited nature of petroleum resources and the environmental impact of the extraction and processing processes make the raw material supply of carboxylated styrene-butadiene latex face sustainability challenges.

[0005] Environmental impact of the production process: Traditional emulsion polymerization processes usually require the use of a large amount of chemical auxiliaries such as emulsifiers and initiators. These auxiliaries may generate pollutants such as wastewater and waste gas during the production process, and improper treatment will cause secondary pollution to the environment.

[0006] Although there are currently some studies on degradable polymer materials, there is no mature and effective technical solution for the preparation of degradable carboxylated styrene-butadiene latex. Some studies have tried to improve its degradation performance by adding degradable additives, but this often leads to a decline in the original performance of the latex, such as a decrease in adhesive strength and a deterioration in film-forming quality. Therefore, developing a preparation method that can not only ensure the original excellent performance of carboxylated styrene-butadiene latex but also have degradable characteristics has become an urgent problem to be solved. Summary of the Invention

[0007] The present invention provides a preparation method of degradable carboxylated styrene-butadiene latex, comprising the following steps:

[0008] Prepare raw materials, including butadiene, styrene, degradable cyclic monomer, emulsifier, initiator, and deionized water. The amount of deionized water used is 180-200% of the total mass of the monomers; the degradable cyclic monomer is lactide or glycolide, and the mass ratio of butadiene, styrene, and degradable cyclic monomer is 30-45:25-40:20-35.

[0009] Purify butadiene and styrene, and purify or dry the degradable cyclic monomer.

[0010] Add the monomer, emulsifier, initiator and deionized water into the reaction kettle. After purging with nitrogen to remove air, carry out emulsion polymerization reaction. The reaction temperature is 50 - 70 °C, and the reaction time is 4 - 8 hours.

[0011] After the reaction is completed, carry out post-treatment on the product, adjust the pH value, remove the unreacted monomer and impurities to obtain the degradable carboxylated styrene - butadiene latex.

[0012] Furthermore: The emulsifier is one or a combination of more than one of sodium dodecyl sulfate, Tween - 80, Span - 60, cetyltrimethylammonium bromide, polyoxyethylene lauryl ether, and the dosage of the emulsifier is 2.5% - 3.5% of the total mass of the monomer.

[0013] Furthermore: The initiator is one or more of potassium persulfate, ammonium persulfate, azobisisobutyronitrile, azobisisoheptonitrile, and the dosage of the initiator is 0.4% - 0.6% of the total mass of the monomer.

[0014] Furthermore: During the polymerization reaction, ultrasonic assistance is adopted. Set the ultrasonic frequency to 30 - 50 kHz, the power to 200 - 400 W, and the ultrasonic dispersion time to 10 - 20 minutes.

[0015] Furthermore: Before the polymerization reaction, form a microemulsion system with the monomer, emulsifier and deionized water under the conditions of a stirring speed of 700 - 900 r / min and a temperature of 25 - 35 °C, and then add the initiator to carry out the polymerization reaction.

[0016] Furthermore: Prepared by the above - mentioned preparation method, the polymer in the latex contains degradable cyclic monomer units, and the average particle size of the latex particles is between 80 - 150 nm.

[0017] Furthermore: In the simulated natural environment degradation experiment, after 3 - 6 months, the mass loss of the latex film reaches 20% - 40%.

[0018] Furthermore: The preparation method of the degradable carboxylated styrene - butadiene latex further includes the following steps:

[0019] Prepare raw materials, including butadiene, bio - based styrene, glycolide, emulsifier, initiator, deionized water and degradable polycaprolactone nanoparticles. The mass ratio of butadiene, bio - based styrene, and glycolide is 35 - 40:30 - 35:25 - 30, and the dosage of the polycaprolactone nanoparticles is 2% - 4% of the total mass of the monomer.

[0020] Purify the monomer, and prepare the polycaprolactone nanoparticles by the solvent evaporation method.

[0021] Add monomers, emulsifier, initiator and deionized water into the reaction kettle, introduce nitrogen to remove air, react at 55 - 65 °C for 3 - 4 hours, then add polycaprolactone nanoparticles and continue to react for 1 - 3 hours.

[0022] After the reaction is completed, post - treat the product, adjust the pH value, remove unreacted monomers and impurities to obtain a degradable carboxylated styrene - butadiene latex containing degradable nano - fillers.

[0023] Furthermore: It also includes the following steps:

[0024] Prepare raw materials, including butadiene, bio - based styrene, glycolide, emulsifier, deionized water; butadiene, bio - based styrene, and glycolide are mixed in a mass ratio of 35 - 40:30 - 35:25 - 30, and the dosage of the emulsifier is 2.8% - 3.2% of the total mass of the monomers.

[0025] Carry out dehydration, impurity removal and refining treatment on the monomers.

[0026] Add monomers, emulsifier and deionized water into a transparent polymerization container, stir evenly and then place it under a cobalt - 60 radiation source, control the radiation dose rate at 4 - 6 Gy / min, the total radiation dose at 15 - 25 kGy, and carry out radiation - induced polymerization reaction at room temperature.

[0027] After the radiation is completed, post - treat the product, adjust the pH value, remove unreacted monomers and impurities to obtain a degradable carboxylated styrene - butadiene latex.

[0028] Furthermore: It also includes the following steps:

[0029] Prepare two groups of monomers. The first group is butadiene, styrene, acrylic acid, and the second group is glycolide, methyl methacrylate, butyl acrylate; at the same time, prepare a compound emulsifier, initiator, and deionized water.

[0030] The first group of monomers butadiene, styrene, acrylic acid are mixed in a mass ratio of 35 - 45:25 - 35:10 - 15, the second group of monomers glycolide, methyl methacrylate, butyl acrylate are mixed in a mass ratio of 25 - 35:35 - 45:20 - 30, the total dosage of the compound emulsifier is 3.0% - 3.8% of the total mass of the two groups of monomers, and the initiator is used for the polymerization of the two groups of monomers respectively.

[0031] Carry out conventional refining treatment on the monomers to remove impurities and inhibitors.

[0032] First, add the first group of monomers, part of the compound emulsifier, the corresponding initiator and part of the deionized water into the reaction kettle, introduce nitrogen to remove air, heat up to 60 - 70 °C, and react for 2 - 4 hours to form the first group of polymer emulsions.

[0033] Then, the second group of monomers, the remaining compound emulsifier, the corresponding initiator and the remaining deionized water are added to the first group of polymer emulsions, and the reaction is continued at 65-75° C. for 3-5 hours to allow the two groups of polymers to penetrate each other to form an interpenetrating network structure.

[0034] After the reaction is completed, the product is post-treated to adjust the pH value, remove unreacted monomers and impurities, and obtain a degradable carboxylated styrene-butadiene latex with an emulsion interpenetrating network structure.

[0035] Beneficial technical effects:

[0036] Good degradability: By introducing degradable cyclic monomers, degradable cross-linking agents and using bio-based monomers, the prepared carboxylated styrene butadiene latex can be gradually degraded by microorganisms or factors such as light and water in the natural environment, effectively reducing pollution to the environment and meeting environmental protection requirements.

[0037] Performance balance: While achieving biodegradability, the original good adhesion, film-forming properties, water resistance and other properties of carboxylated styrene butadiene latex are maintained by optimizing the polymerization process and formula design, meeting the application needs of different industrial fields.

[0038] Sustainable development: Using bio-based monomers to replace some traditional petroleum-based monomers reduces dependence on limited petroleum resources, achieves a sustainable supply of raw materials, and provides technical support for the sustainable development of related industries.

[0039] Green production: The use of green synthesis methods such as supercritical carbon dioxide-assisted polymerization technology and microwave-assisted synthesis technology reduces the use of traditional organic solvents and chemical additives, reduces environmental pollution in the production process, and is in line with the concept of green chemistry.

[0040] Versatility: Through different innovative methods, such as photoinitiated polymerization combined with degradable photosensitizers, enzymatic synthesis and chemical polymerization synergistic processes, latex is endowed with some unique properties, such as photoresponsiveness and biocatalytic degradation, which expands its application areas. DETAILED DESCRIPTION

[0041] Example 1

[0042] Preparation of lactide-butadiene-styrene copolymer latex:

[0043] Material preparation:

[0044] Prepare raw materials: butadiene, styrene, lactide, sodium dodecyl sulfate (SDS) as an emulsifier, potassium persulfate (KPS) as an initiator, deionized water, and a degradable crosslinking agent. Mix butadiene, styrene, and lactide in a mass ratio of 40:30:30. The dosage of emulsifier SDS is 3% of the total mass of the monomers, the dosage of initiator KPS is 0.5% of the total mass of the monomers, and the dosage of deionized water is 200% of the total mass of the monomers.

[0045] Monomer purification: Subject butadiene and styrene to vacuum distillation to remove the inhibitors and impurities therein. Recrystallize and purify lactide before use to ensure the monomer purity.

[0046] Polymerization process:

[0047] The first step of emulsion polymerization: Add 70% of the deionized water, 50% of the SDS, butadiene, styrene, and 30% of the lactide to a reaction kettle equipped with a stirrer, a reflux condenser, and a thermometer. Introduce nitrogen to remove air. After stirring evenly, heat up to 60 °C and react for 2 hours to form a basic polymer chain.

[0048] The second step of in-situ crosslinking and polymerization: Add the remaining deionized water, lactide, degradable crosslinking agent (a crosslinking agent containing disulfide bonds, with a dosage of 2% of the total mass of the monomers), and the remaining SDS, KPS, and degradable crosslinking agent (a crosslinking agent containing disulfide bonds, with a dosage of 2% of the total mass of the monomers). Heat up to 70 °C and continue to react for 4 hours to further insert the degradable cyclic monomers into the polymer chain and form a crosslinked network.

[0049] Post-treatment: After the reaction is completed, cool the latex to room temperature, adjust the pH value to 8 - 9 with ammonia water, and then remove the unreacted monomers and residual solvents by vacuum distillation to obtain a degradable carboxylated styrene-butadiene latex. Determine its molecular weight and distribution by gel permeation chromatography (GPC), characterize its chemical structure using nuclear magnetic resonance hydrogen spectrum (1HNMR) and Fourier transform infrared spectroscopy (FTIR), and observe the morphology of the latex particles by scanning electron microscopy (SEM). The results show that the latex has good stability, the polymer molecular weight distribution is relatively narrow, lactide is successfully inserted into the polymer chain, and the latex particles are spherical and evenly distributed. In the soil burial degradation experiment, after 3 months, the mass loss of the latex film reaches 30%, proving its good degradability. At the same time, when this latex is used for paper coating, compared with the traditional carboxylated styrene-butadiene latex, the bonding strength only decreases by 5%, but the degradability is significantly improved.

[0050] Example 2

[0051] Preparation of bio-based butadiene-bio-based styrene-glycolide copolymer latex:

[0052] Material preparation:

[0053] Raw material preparation: Bio-based butadiene, bio-based styrene, glycolide, sodium dodecyl sulfate (SDS) as an emulsifier, azobisisobutyronitrile (AIBN) as an initiator, and deionized water. Bio-based butadiene, bio-based styrene, and glycolide are mixed at a mass ratio of 35:35:30. The dosage of emulsifier SDS is 2.5% of the total mass of the monomers, the dosage of initiator AIBN is 0.4% of the total mass of the monomers, and the dosage of deionized water is 180% of the total mass of the monomers.

[0054] Monomer treatment: Bio-based butadiene and bio-based styrene are dried before use to remove moisture and impurities. Glycolide is purified by sublimation to improve its purity.

[0055] Polymerization process:

[0056] Supercritical carbon dioxide-assisted polymerization: The monomers, emulsifier, initiator, and part of the deionized water are added to a high-pressure reactor. Supercritical carbon dioxide is introduced, and the pressure is controlled at 10 MPa and the temperature at 50 °C. After stirring evenly, the polymerization reaction is initiated, and the reaction time is 6 hours. During the polymerization process, the reaction rate and the molecular weight distribution of the polymer are controlled by adjusting the flow rate and pressure of supercritical carbon dioxide.

[0057] Post-treatment: After the reaction, supercritical carbon dioxide is slowly released. The latex is transferred to a separating funnel, allowed to stand and separate layers, and the lower aqueous phase is removed. Then, the residual monomers and solvents are removed using a rotary evaporator to obtain a degradable carboxylated styrene-butadiene latex. The content of bio-based monomers is determined by elemental analysis, and the glass transition temperature and crystallization properties of the latex are measured using differential scanning calorimetry (DSC). The results show that the bio-based monomers have successfully participated in the polymerization reaction, the glass transition temperature of the latex is appropriate, and the crystallization properties are good. In the marine environment simulation degradation experiment, after 4 months, the mass loss of the latex film reaches 25%, showing good degradability. When this latex is used in the adhesive formulation, compared with traditional products, its environmental performance is greatly improved, and under normal use conditions, the bonding performance is basically equivalent.

[0058] Example 3

[0059] Synergistic preparation of latex by enzymatic synthesis and chemical polymerization:

[0060] Material preparation:

[0061] Prepare raw materials: Butadiene, styrene, lactide, lipase (immobilized on a silica gel carrier), potassium persulfate (KPS), sodium dodecylbenzenesulfonate (SDBS) as an emulsifier, and deionized water. Butadiene, styrene, and lactide are mixed at a mass ratio of 45:25:30. The dosage of emulsifier SDBS is 3% of the total mass of the monomers, the dosage of KPS is 0.6% of the total mass of the monomers, the dosage of lipase is 5% of the mass of lactide, and the dosage of deionized water is 220% of the total mass of the monomers.

[0062] Monomer purification: Butadiene and styrene are subjected to alkali washing, water washing and then drying treatment, and lactide is purified by recrystallization.

[0063] Polymerization process:

[0064] Enzymatic synthesis: Lactide, lipase and partial deionized water are added to the reaction kettle, and stirred at 40 °C for 3 hours to carry out ring-opening polymerization of lactide under the catalysis of lipase to form a prepolymer.

[0065] Chemical polymerization: Butadiene, styrene, emulsifier SDBS and initiator KPS are added, nitrogen is introduced to remove air, the temperature is raised to 65 °C, and the reaction is carried out for 5 hours to carry out copolymerization reaction of butadiene, styrene and the prepolymer.

[0066] Post-treatment: After the reaction, the latex is centrifuged to remove the unreacted lipase, then the pH value is adjusted to 7 - 8 with dilute hydrochloric acid, and then the unreacted monomers and solvents are removed by vacuum distillation to obtain degradable carboxylated styrene-butadiene latex. The structure and molecular weight of the polymer are analyzed by gel permeation chromatography (GPC) and nuclear magnetic resonance hydrogen spectrum (1HNMR), and the morphology of the latex particles is observed by scanning electron microscope (SEM). The results show that the latex particles are of uniform size, the polymer has the expected structure, and the molecular weight distribution is narrow. In the compost degradation experiment, after 2 months, the mass loss of the latex film reaches 40%, indicating its excellent degradability. Applying this latex to the coating formulation adds environmental protection advantages to the coating product while ensuring good film-forming performance and water resistance.

[0067] Example 4

[0068] Preparation of latex by photoinitiated polymerization combined with degradable photosensitizer:

[0069] Material preparation:

[0070] Raw material preparation: Butadiene, styrene, glycolide, benzophenone-based degradable photosensitizer (such as 4-hydroxybenzophenone propionate), sodium dodecyl sulfate (SDS) as emulsifier, deionized water. Butadiene, styrene and glycolide are mixed in a mass ratio of 40:30:30. The dosage of emulsifier SDS is 3.5% of the total mass of the monomers, the dosage of the degradable photosensitizer is 1% of the total mass of the monomers, and the dosage of deionized water is 200% of the total mass of the monomers.

[0071] Monomer treatment: Butadiene and styrene are refined by distillation, and glycolide is dried.

[0072] Polymerization process:

[0073] Photoinitiated polymerization: Monomers, emulsifier, degradable photosensitizer, and deionized water were added to a reaction kettle equipped with a quartz window. Nitrogen was introduced to remove air. After stirring evenly, the reaction kettle was irradiated with ultraviolet light at a wavelength of 365 nm and reacted at 50 °C for 4 hours to initiate the polymerization reaction.

[0074] Post-treatment: After the reaction, the pH value of the latex was adjusted to 8 - 9 with ammonia water, and then the unreacted monomers and solvents were removed by vacuum distillation to obtain degradable carboxylated styrene-butadiene latex. The content and distribution of the degradable photosensitizer in the latex were determined by ultraviolet-visible absorption spectroscopy (UV-Vis), and the structure and molecular weight of the polymer were analyzed by Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC). The results showed that the degradable photosensitizer was evenly distributed in the latex, and the polymer had good structure and molecular weight distribution. In the light degradation experiment, under simulated sunlight irradiation, after 1 month, the mass loss of the latex film reached 20%, showing light-responsive degradable performance. When this latex was used for textile coating, it not only imparted good adhesion and waterproof properties to the textiles, but also made them have environmentally friendly degradable characteristics.

[0075] Example 5: Preparation of latex by microwave-assisted synthesis and in-situ generation of degradable additives

[0076] Material preparation:

[0077] Monomers: Butadiene, styrene, and lactide were accurately weighed according to the mass ratio of 40:30:30. Butadiene and styrene are conventional monomers of carboxylated styrene-butadiene latex, providing the basic polymer backbone structure. Lactide, as a degradable cyclic monomer, the ester bond in its molecule is the key factor for the degradable performance of the latex. Before use, butadiene was washed with alkali to remove the inhibitor, and styrene was purified by vacuum distillation to ensure the high purity of the monomers and avoid the adverse effects of impurities on the polymerization reaction. Lactide was refined by recrystallization to further improve its purity.

[0078] Emulsifier: Sodium dodecyl sulfate, with a dosage of 3% of the total mass of the monomers. It plays a role in reducing the surface tension at the oil-water interface in the reaction system, enabling the monomers to be evenly dispersed in the aqueous phase to form a stable emulsion system, providing a good reaction environment for the subsequent polymerization reaction.

[0079] Initiator: Potassium persulfate, with a dosage of 0.5% of the total mass of the monomers. Potassium persulfate can decompose to generate free radicals under heating or light irradiation, initiating the polymerization reaction of the monomers, which is the key substance for starting the polymerization process.

[0080] Degradable additive precursor: A polymer precursor containing hydrolyzable groups is selected, such as poly(vinyl alcohol-co-ethyl acrylate), and its dosage is 5% of the total mass of the monomers. This polymer precursor can undergo hydrolysis reactions under specific conditions to in-situ generate additives with degradable functions, enhancing the degradable performance of the latex.

[0081] Reaction medium: Deionized water, with a dosage of 200% of the total mass of the monomers. As the solvent for the reaction, deionized water can not only dissolve substances such as emulsifiers and initiators but also provide a homogeneous environment for the dispersion and polymerization reactions of the monomers.

[0082] Polymerization process:

[0083] Mixing and deoxygenation: The accurately weighed and refined butadiene, styrene, lactide monomers, as well as sodium dodecyl sulfate emulsifier, potassium persulfate initiator, poly(vinyl alcohol-co-ethyl acrylate) polymer precursor, and deionized water are successively added to a reaction kettle equipped with a microwave device. During the addition of the raw materials, the stirring device is turned on and stirred at a speed of 300 r / min to ensure uniform mixing of each component. Subsequently, nitrogen is introduced into the reaction kettle for 30 minutes to fully remove the air in the reaction system. Since oxygen has an inhibitory effect on polymerization and will inhibit the progress of the polymerization reaction, it must be completely removed.

[0084] Microwave-assisted polymerization: Under nitrogen protection, the microwave device is turned on, and the microwave power is set to 600 W and the frequency to 2450 MHz. The rapid heating and uniform heating characteristics of the microwave can quickly raise the temperature of the reaction system to 70 °C and maintain stability at this temperature. Under the action of microwave radiation, potassium persulfate decomposes to generate free radicals, initiating the emulsion polymerization reactions of butadiene, styrene, and lactide. During the reaction process, continuous stirring is carried out, and the stirring speed is increased to 500 r / min to ensure the uniformity of the reaction system. The polymerization reaction proceeds for 4 hours. During this period, the monomers continuously polymerize to form polymer chains, and at the same time, the ester bonds of the lactide monomers are introduced into the polymer molecular chains, endowing the latex with degradable properties.

[0085] In-situ generation of additives: When the polymerization reaction proceeds for 2 hours, due to the continuous action of the microwave, the temperature and energy distribution in the system are uniform, and the polymer precursor poly(vinyl alcohol-co-ethyl acrylate) begins to undergo hydrolysis reactions. The ester bonds in its molecules are broken under the action of water, gradually in-situ generating additives with degradable functions. These additives can interact with the polymer chains that are being polymerized, further enhancing the degradable performance of the latex without affecting other properties of the latex.

[0086] Post-treatment steps:

[0087] Adjusting the pH value: After the polymerization reaction is completed, take out the reaction kettle from the microwave device and let it cool naturally to room temperature. Then, slowly drop dilute ammonia water into the reaction system while continuously stirring to adjust the pH value of the latex to 8 - 9. This pH range can ensure the stability of the latex and avoid phenomena such as coagulation during subsequent processing.

[0088] Removing unreacted monomers: Using the method of vacuum distillation, transfer the latex with adjusted pH value to the distillation device. Under reduced pressure, gradually raise the temperature to 50 °C to volatilize the unreacted butadiene, styrene, and lactide monomers, and collect these monomers through the condensation device to achieve resource recycling. The vacuum distillation process lasts for 2 hours to ensure that the unreacted monomers are fully removed.

[0089] Filtration and purification: The latex after vacuum distillation is filtered through a 0.45 μm microporous membrane to remove possible impurities, aggregates, or incompletely reacted particles. The filtered latex is the target product - degradable carboxylated styrene - butadiene latex.

[0090] Performance testing and analysis:

[0091] Degradability testing: Make the prepared degradable carboxylated styrene - butadiene latex into a film with a thickness of 0.5 mm and place it in a degradation chamber simulating the natural soil environment. Under the conditions of a temperature of 25 °C and a humidity of 70%, regularly take out the film and measure its mass loss by the weighing method. After 3 months of degradation experiments, it is found that the mass loss of the latex film reaches 35%, indicating that the latex has good degradability.

[0092] Testing of other properties: Test the adhesion property of the latex. Coat the latex on two standard wood specimens and conduct the test according to the standard adhesion test method. The results show that its adhesion strength reaches 1.5 MPa, which is equivalent to that of traditional carboxylated styrene - butadiene latex. At the same time, observe the film - forming property of the latex and find that the formed film is uniform, dense, and has good flexibility and gloss.

[0093] Example 6

[0094] Preparation of latex by ultrasonic - assisted emulsion polymerization

[0095] Material preparation:

[0096] Prepare butadiene, bio - based styrene, glycolide, Tween - 80 as an emulsifier, azodiisooctanenitrile (ABVN) as an initiator, and deionized water. Mix butadiene, bio - based styrene, and glycolide in a mass ratio of 38:32:30. The dosage of emulsifier Tween - 80 is 2.8% of the total mass of the monomers, the dosage of initiator ABVN is 0.45% of the total mass of the monomers, and the dosage of deionized water is 190% of the total mass of the monomers.

[0097] The butadiene is subjected to alkali washing to remove the polymerization inhibitor, the bio-based styrene is further purified by vacuum distillation, and the glycolide is dried to a constant weight in a vacuum drying oven.

[0098] Polymerization process:

[0099] The monomers, emulsifier, initiator, and deionized water are added to a reaction kettle equipped with an ultrasonic generator. Nitrogen is first introduced for 15 minutes to remove the air in the system, and then the ultrasonic wave is turned on, with the frequency set at 40 kHz and the power at 300 W.

[0100] Ultrasonic dispersion is carried out at 25 °C for 15 minutes to uniformly disperse the monomers in the aqueous phase to form a stable emulsion. Subsequently, the temperature is raised to 55 °C, and the polymerization reaction is carried out under the continuous action of ultrasonic waves for 5 hours. The cavitation effect of ultrasonic waves can accelerate the polymerization rate of monomers and simultaneously refine the size of latex particles.

[0101] Post-treatment: After the reaction is completed, the latex is cooled to room temperature, and the pH value is adjusted to about 8 with sodium hydroxide solution. Then, unreacted impurities and possible condensates are removed by high-speed centrifugation, and the unreacted monomers are evaporated under reduced pressure using a thin-film evaporator to obtain a degradable carboxylated styrene-butadiene latex. The particle size distribution of the latex particles is measured by dynamic light scattering (DLS), and the results show that the average particle size is between 100 - 120 nm and the distribution is relatively uniform. In the simulated fresh water environment degradation experiment, after 5 months, the mass loss of the latex film reaches 22%, indicating its certain degradable performance. Applying this latex to leather finishing shows environmental protection advantages while maintaining good softness and gloss.

[0102] Example 7

[0103] Preparation of latex by microemulsion polymerization combined with degradable nano-fillers

[0104] Material preparation:

[0105] Select butadiene, bio-based styrene, glycolide, a compound emulsifier of Span-60 and Tween-60 (mass ratio 2:3), ammonium persulfate (APS) as the initiator, deionized water, and degradable polycaprolactone (PCL) nanoparticles. Butadiene, bio-based styrene, and glycolide are mixed in a mass ratio of 42:28:30. The total amount of emulsifier used is 3.2% of the total mass of the monomers, the amount of initiator APS used is 0.55% of the total mass of the monomers, the amount of deionized water used is 210% of the total mass of the monomers, and the amount of PCL nanoparticles used is 3% of the total mass of the monomers.

[0106] The monomers were subjected to conventional purification treatment. PCL nanoparticles were prepared by the solvent evaporation method. PCL was dissolved in dichloromethane and then slowly added dropwise to vigorously stirred water. After the dichloromethane had evaporated, the PCL nanoparticles were collected by centrifugation and dried.

[0107] Polymerization process:

[0108] First, an emulsifier, deionized water, and monomers were added to a reaction kettle to form a microemulsion system under stirring conditions. The stirring speed was controlled at 800 r / min, and the temperature was maintained at 30 °C.

[0109] An initiator APS was added, and then the temperature of the reaction kettle was raised to 60 °C and reacted for 3 hours. Then PCL nanoparticles were added and the reaction continued for 2 hours to uniformly disperse the nanoparticles in the latex and have a certain degree of interaction with the polymer chains.

[0110] Post-treatment: After the reaction was completed, the latex was cooled to room temperature, and the pH value was adjusted to 8.5 with dilute ammonia water. Unreacted monomers and small molecule impurities were removed by ultrafiltration to obtain carboxylated styrene-butadiene latex containing degradable nano-fillers. It was observed by transmission electron microscopy (TEM) that the PCL nanoparticles were uniformly dispersed inside or on the surface of the latex particles. In the simulated soil microbial degradation experiment, after 3.5 months, the mass loss of the latex film reached 32%, proving its good degradability. When this latex was used as a wood adhesive, compared with the latex without nano-fillers, the bonding strength increased by 8% while maintaining the degradable characteristics.

[0111] Example 8

[0112] Preparation of degradable carboxylated styrene-butadiene latex by radiation-induced polymerization

[0113] Material preparation:

[0114] Prepare butadiene, bio-based styrene, glycolide, dodecyltrimethylammonium bromide (DTAB) as an emulsifier, and deionized water. Butadiene, bio-based styrene, and glycolide were mixed in a mass ratio of 36:34:30. The amount of emulsifier DTAB used was 3% of the total mass of the monomers, and the amount of deionized water used was 200% of the total mass of the monomers.

[0115] Butadiene and bio-based styrene were dehydrated and decontaminated, and glycolide was recrystallized and refined.

[0116] Polymerization process:

[0117] The monomers, emulsifier, and deionized water were added to a special transparent polymerization container and stirred evenly to form a stable emulsion system. Then the container was placed under a cobalt-60 radiation source, and the radiation dose rate was controlled at 5 Gy / min, and the total radiation dose was 20 kGy.

[0118] The radiation-induced polymerization reaction is carried out at room temperature, and continuous stirring is performed during the radiation process to make the reaction system uniformly heated and receive radiation. The radiation induces the monomer to generate free radicals, thereby initiating the polymerization reaction.

[0119] Post-treatment: After the radiation ends, the latex is transferred to a separatory funnel, allowed to stand for stratification, and the possible impurities in the lower layer are removed. Then, the pH value is adjusted to 7 - 8 with hydrochloric acid, and the unreacted monomer is removed by vacuum distillation to obtain the degradable carboxylated styrene-butadiene latex. The polymer structure is characterized by Fourier transform infrared spectroscopy (FTIR) and nuclear magnetic resonance carbon spectroscopy (13CNMR) to confirm that glycolide is successfully polymerized into the molecular chain. In the simulated composting environment degradation experiment, after 2.5 months, the mass loss of the latex film reaches 38%, showing good degradable performance. Using this latex for paper packaging adhesives not only meets the bonding requirements of packaging but also has the characteristics of environmental protection and degradability, meeting the current development trend of green packaging.

[0120] Example 9

[0121] Preparation of latex with controlled structure by reversible addition-fragmentation chain transfer (RAFT) polymerization

[0122] Material preparation:

[0123] Prepare butadiene, styrene, lactide, isobutyronitrile dithiobenzoate (CPDB) as the RAFT reagent, azobisisobutyronitrile (AIBN) as the initiator, polyoxyethylene lauryl ether (Brij-35) as the emulsifier, and deionized water. Butadiene, styrene, and lactide are mixed in a mass ratio of 40:30:30. The dosage of the RAFT reagent CPDB is 1.2% of the total mass of the monomers, the dosage of the initiator AIBN is 0.4% of the total mass of the monomers, the dosage of the emulsifier Brij-35 is 3.3% of the total mass of the monomers, and the dosage of deionized water is 200% of the total mass of the monomers.

[0124] Perform conventional purification treatment on the monomers to ensure the purity of the monomers.

[0125] Polymerization process:

[0126] Add the monomers, RAFT reagent, initiator, emulsifier, and deionized water into the reaction kettle, and introduce nitrogen for 30 minutes to remove the oxygen in the system.

[0127] Heat up to 70 °C and carry out emulsion polymerization reaction under stirring conditions for 6 hours. The RAFT reagent can effectively control the molecular weight and molecular weight distribution of the polymer, realizing precise regulation of the polymer structure.

[0128] Post-treatment: After the reaction, the latex was cooled to room temperature, and the pH value was adjusted to 8 with sodium bicarbonate solution. The polymer in the latex was precipitated by the precipitation method, washed repeatedly with ethanol to remove impurities such as unreacted monomers, RAFT reagents, and emulsifiers, and then redispersed in deionized water to obtain a structurally controllable degradable carboxylated styrene-butadiene latex. The molecular weight and its distribution of the polymer were determined by gel permeation chromatography (GPC). The results showed that the polydispersity index (PDI) was between 1.2 and 1.3, indicating that the polymer had a narrow molecular weight distribution. In the simulated marine microorganism degradation experiment, after 4.5 months, the mass loss of the latex film reached 28%, proving its good degradability. This latex was used in waterborne coatings, with excellent film-forming properties. The water resistance and weather resistance of the coating film were comparable to those of traditional latex coatings, and it had the advantage of being degradable.

[0129] Example 10

[0130] Preparation of Degradable Latex with Emulsion Interpenetrating Polymer Network (IPN) Structure

[0131] Material Preparation:

[0132] Prepare two groups of monomers. The first group is butadiene, styrene, and acrylic acid (AA), and the second group is glycolide, methyl methacrylate (MMA), and butyl acrylate (BA). At the same time, prepare a compound emulsifier of sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB), potassium persulfate (KPS) and azobisisobutyronitrile (AIBN) as initiators, and deionized water.

[0133] The first group of monomers butadiene, styrene, and acrylic acid were mixed in a mass ratio of 40:30:10, and the second group of monomers glycolide, methyl methacrylate, and butyl acrylate were mixed in a mass ratio of 30:40:30. The mass ratio of SDS to CTAB in the compound emulsifier was 3:2, and the total amount used was 3.5% of the total mass of the two groups of monomers. KPS was used for the polymerization of the first group of monomers, and the amount used was 0.5% of the total mass of the first group of monomers. AIBN was used for the polymerization of the second group of monomers, and the amount used was 0.4% of the total mass of the second group of monomers. The amount of deionized water used was 220% of the total mass of the two groups of monomers.

[0134] The monomers were subjected to conventional purification treatment to remove impurities and inhibitors.

[0135] Polymerization Process:

[0136] First, the first group of monomers, half of the compound emulsifier, KPS, and half of the deionized water were added to the reaction kettle, nitrogen was introduced to remove air, and the temperature was raised to 65 °C and reacted for 3 hours to form the first group of polymer latex.

[0137] Then, the second group of monomers, the remaining compound emulsifier, AIBN, and the remaining deionized water were added to the first group of polymer emulsion, and the reaction was continued at 70 °C for 4 hours to allow the two groups of polymers to penetrate each other and form an interpenetrating network structure.

[0138] Post-treatment: After the reaction, the latex was cooled to room temperature, and the pH value was adjusted to 8.2 with sodium hydroxide solution. The possible condensates were removed by centrifugation, and the unreacted monomers were removed by vacuum distillation to obtain a degradable carboxylated styrene-butadiene latex with an emulsion interpenetrating network structure. It was observed by scanning electron microscopy (SEM) that the two groups of polymers formed an intertwined network structure. In the simulated natural environment degradation experiment, after 3 months, the mass loss of the latex film reached 35%, showing good degradability. When this latex was used for fabric coating, it not only imparted good adhesion and flexibility to the fabric, but also reduced the potential harm to the environment due to its degradability.

Claims

1. A method for preparing a degradable carboxylated styrene-butadiene latex, characterized in that: The following steps are involved: Prepare raw materials, including butadiene, styrene, a degradable cyclic monomer, an emulsifier, an initiator and deionized water, wherein the amount of deionized water is 180-200% of the total mass of the monomers; the degradable cyclic monomer is lactide or glycolide, and the mass ratio of butadiene, styrene and the degradable cyclic monomer is 30-45:25-40:20-35; Refining butadiene and styrene, purifying or drying the degradable cyclic monomers; Add monomers, emulsifiers, initiators and deionized water into a reactor, introduce nitrogen to exclude air, and then carry out emulsion polymerization at a reaction temperature of 50-70°C for 4-8 hours; After the reaction is finished, the product is post-treated to adjust the pH value, remove unreacted monomers and impurities, and obtain degradable carboxylated styrene-butadiene latex.

2. The method for preparing the degradable carboxylated styrene-butadiene latex according to claim 1, wherein: The emulsifier is a compound of one or more of sodium dodecyl sulfate, Tween-80, Span-60, hexadecyl trimethyl ammonium bromide and polyoxyethylene lauryl ether, and the amount of the emulsifier is 2.5%-3.5% of the total weight of the monomers.

3. The method for preparing the degradable carboxylated styrene-butadiene latex according to claim 1, wherein: The initiator is one or more of potassium persulfate, ammonium persulfate, azobisisobutyronitrile and azobisisoheptanenitrile, and the amount of the initiator is 0.4%-0.6% of the total weight of the monomers.

4. The method for preparing the degradable carboxylated styrene-butadiene latex according to claim 1, characterized in that: During the polymerization reaction, ultrasonic assistance is used, and the ultrasonic frequency is set to 30-50kHz, the power is set to 200-400W, and the ultrasonic dispersion time is set to 10-20 minutes.

5. The method for preparing the degradable carboxylated styrene-butadiene latex according to claim 1, characterized in that: Before the polymerization reaction, the monomer, emulsifier and deionized water are stirred at a speed of 700-900 r / min and a temperature of 25-35° C. to form a microemulsion system, and then an initiator is added to carry out the polymerization reaction.

6. A degradable carboxylated styrene-butadiene latex, characterized in that: The latex is prepared by the preparation method according to any one of claims 1 to 5, wherein the polymer in the latex contains degradable cyclic monomer units, and the average particle size of the latex particles is between 80 and 150 nm.

7. The degradable carboxylated styrene-butadiene latex according to claim 6, characterized in that: In the simulated natural environment degradation experiment, after 3-6 months, the mass loss of the latex film reached 20%-40%.

8. A method for preparing a degradable carboxylated styrene-butadiene latex, characterized in that: The following steps are involved: Prepare raw materials, including butadiene, bio-based styrene, glycolide, emulsifier, initiator, deionized water and degradable polycaprolactone nanoparticles, the mass ratio of butadiene, bio-based styrene and glycolide is 35-40:30-35:25-30, and the amount of polycaprolactone nanoparticles is 2%-4% of the total mass of the monomers; The monomers are refined and polycaprolactone nanoparticles are prepared by a solvent evaporation method; Add monomer, emulsifier, initiator and deionized water into the reaction kettle, introduce nitrogen to exclude air, react at 55-65°C for 3-4 hours, then add polycaprolactone nanoparticles and continue to react for 1-3 hours; After the reaction is completed, the product is post-treated to adjust the pH value, remove unreacted monomers and impurities, and obtain a degradable carboxylated styrene-butadiene latex containing degradable nanofillers.

9. A method for preparing a degradable carboxylated styrene-butadiene latex, characterized in that: The following steps are involved: Prepare raw materials, including butadiene, bio-based styrene, glycolide, emulsifier, and deionized water; butadiene, bio-based styrene, and glycolide are mixed in a mass ratio of 35-40:30-35:25-30, and the amount of emulsifier is 2.8%-3.2% of the total weight of the monomers; The monomer is subjected to water removal, impurity removal and refining treatment; Add monomers, emulsifiers and deionized water into a transparent polymerization container, stir evenly and place under a cobalt-60 radiation source, control the radiation dose rate to 4-6Gy / min, the total radiation dose to 15-25kGy, and conduct radiation-induced polymerization at room temperature; After the radiation is finished, the product is post-treated to adjust the pH value, remove unreacted monomers and impurities, and obtain the degradable carboxylated styrene-butadiene latex.

10. A method for preparing a degradable carboxylated styrene-butadiene latex, characterized in that: The following steps are involved: Prepare two groups of monomers, the first group is butadiene, styrene, acrylic acid, and the second group is glycolide, methyl methacrylate, butyl acrylate; prepare compound emulsifier, initiator, and deionized water at the same time; The first group of monomers, butadiene, styrene, and acrylic acid, are mixed in a mass ratio of 35-45:25-35:10-15, and the second group of monomers, glycolide, methyl methacrylate, and butyl acrylate, are mixed in a mass ratio of 25-35:35-45:20-30, and the total amount of the compound emulsifier is 3.0%-3.8% of the total mass of the two groups of monomers. The initiator is used for the polymerization of the two groups of monomers respectively; The monomers are subjected to conventional refining treatment to remove impurities and inhibitors; Firstly, the first group of monomers, part of the compound emulsifier, the corresponding initiator and part of the deionized water are added into the reaction kettle, nitrogen is introduced to exclude the air, the temperature is raised to 60-70° C., and the reaction is carried out for 2-4 hours to form the first group of polymer emulsions; Then, the second group of monomers, the remaining compound emulsifier, the corresponding initiator and the remaining deionized water are added to the first group of polymer emulsions, and the reaction is continued at 65-75° C. for 3-5 hours, so that the two groups of polymers penetrate each other to form an interpenetrating network structure; After the reaction is completed, the product is post-treated to adjust the pH value, remove unreacted monomers and impurities, and obtain a degradable carboxylated styrene-butadiene latex with an emulsion interpenetrating network structure.