Natural latex grafted high-elastic synthetic emulsion preparation formula and method thereof

Abstract

The invention relates to the technical field of natural latex grafted polymer emulsion products, in particular to a preparation formula and a preparation method of natural latex grafted high-elasticity synthetic emulsion. The high-elasticity synthetic emulsion comprises the following components in percentage by weight of dry substances: a matrix component which is composed of 30-32% of natural latex and 66% of C4-C5 alkadiene mixture, wherein the natural latex is prepared by centrifuging and concentrating fresh latex of hevea brasiliensis. According to the invention, grafting modification and copolymerization of the natural latex are combined, so that the emulsion has high elasticity of the natural latex and durability of a synthetic emulsion, additives such as an anionic emulsifier, a water-soluble initiator, a chain transfer agent and an alkaline pH regulator are added, and meanwhile, the emulsion adopts the natural latex and a synthetic material which are relatively low in cost; the production cost is reduced, so that the synthesized emulsion integrates the elasticity of the natural latex and the durability of the synthesized emulsion, the cost is low, and the process is stable.

Description

Technical Field

[0001] The present invention relates to the technical field of polymer emulsion products grafted with natural latex, and specifically to a preparation formula and method for a highly elastic synthetic emulsion grafted with natural latex. Background Art

[0002] Due to its high elasticity, excellent flexibility and biocompatibility, natural latex is widely used in medical devices (such as medical gloves, condoms), personal protective equipment (industrial gloves, household gloves), household products (latex mattresses, pillows) and industrial products (sealing rings, shock absorbers), etc.

[0003] Natural latex is not resistant to oil, solvents, and has poor abrasion resistance. It is prone to aging and yellowing during long-term use; the proteins it contains are likely to cause allergic reactions in the human body, leading to contact dermatitis. Moreover, the raw material extraction is significantly affected by regions and climate, resulting in large fluctuations in production volume and quality, and insufficient supply chain stability. The industrial community has tried to replace natural latex with synthetic emulsions (such as styrene-butadiene latex). However, although the existing synthetic emulsions have lower costs, their properties such as elasticity and adhesion are far inferior to those of natural latex and cannot meet the requirements of high-end protective equipment (such as highly elastic labor protection gloves). In addition, although existing modification technologies (such as blending, physical filling) can partially improve the properties, they often sacrifice the stability or processability of the emulsion and cannot simultaneously take into account oil resistance, abrasion resistance and low allergenicity. Therefore, there is an urgent need to design a preparation formula and method for a highly elastic synthetic emulsion grafted with natural latex, which can combine the elasticity of natural latex with the durability of synthetic emulsions, have low costs and stable processes. Summary of the Invention

[0004] The purpose of the present invention is to provide a preparation formula and method for a highly elastic synthetic emulsion grafted with natural latex, so as to solve the problem in the above background art that the existing synthetic emulsions cannot combine the elasticity of natural latex with the durability of synthetic emulsions and have low costs.

[0005] To achieve the above object, the present invention provides the following technical solutions: A highly elastic synthetic emulsion obtained by graft modification of natural latex, comprising the following components by dry matter weight percentage: Matrix component: composed of 30% - 32% of natural latex and 66% of a C4-C5 diolefin mixture, wherein the natural latex is obtained by centrifugal concentration of fresh latex from Hevea brasiliensis, with a solid content > 60%, a protein content < 0.8%, and a volatile content < 1.2%; Functional modification component: 2% - 3% of an acrylate cross-linking monomer, which monomer comprises a composite system composed of methyl methacrylate and butyl acrylate in a ratio of (1:1) - (1:2); Auxiliary agent system: including 0.2% - 0.4% of an anionic emulsifier, 0.2% - 0.3% of a water-soluble initiator, 0.4% of a chain transfer agent, 0.5% - 1% of a basic pH regulator, and deionized water to make up to 100%; wherein the C4-C5 diolefin mixture is a copolymer monomer composed of isoprene and 1,3-butadiene in a dynamic ratio of (3:7) - (7:3).

[0006] Preferably, the anionic emulsifier is branched C12-C14 alkyl alcohol polyoxyethylene ether sulfate or nonylphenol polyoxyethylene ether; the water-soluble initiator is a redox system composed of potassium persulfate and sodium bisulfite in a ratio of (2:1); the chain transfer agent is a molecular weight regulating system composed of dodecyl mercaptan and β-mercaptoethanol in a ratio of (4:1).

[0007] A preparation method of a highly elastic synthetic emulsion obtained by graft modification of natural latex, comprising the following steps:

[0008] (1) Pretreatment: Stabilize the natural latex with a 0.5% - 1.0% ammonia water solution and filter it through a 200-mesh sieve;

[0009] (2) Feeding: Add the treated natural latex into a polymerization kettle, and sequentially add 50% of the total amount of deionized water and all the emulsifiers;

[0010] (3) Replacement: Evacuate to -0.85 MPa and maintain for 10 min to complete oxygen replacement;

[0011] (4) Primary polymerization: Add 50% of the total amount of isoprene and butadiene, heat to 20 - 50 °C and stir for 15 minutes;

[0012] (5) Initiation: Inject 60% of the total amount of the prepared initiator;

[0013] (6) Dropwise polymerization: Mix the remaining 50% of isoprene, butadiene and all the cross-linking monomers, and dropwise add them evenly within 6 - 8 hours, and simultaneously add the remaining 40% of the initiator;

[0014] (7) Aging: React at 50 - 70 °C for 3 - 7 hours;

[0015] (8) Post-treatment: Add ammonia water to adjust the pH to 10.0 ± 0.5, filter and discharge the material.

[0016] Preferably, the temperature of the ammonia water stabilization treatment is 10 - 15 °C, the treatment time is 30 - 60 minutes, the gel content of the latex after filtration through a 200-mesh sieve is ≤ 0.05%, and the pretreated latex is stored in a nitrogen environment to avoid oxidation reaction.

[0017] Preferably, before the vacuum replacement, the polymerization kettle needs to be evacuated in three cycles. Each time it is evacuated to -0.85 MPa and maintained for 5 minutes. After the replacement is completed, nitrogen is filled to normal pressure, and this is repeated three times to thoroughly remove oxygen, and the residual oxygen concentration is ≤ 10 ppm.

[0018] Preferably, the initiator solution is pre-cooled to below 5 °C in an ice-water bath and added in two portions. 60% of the total amount of the initiator is added for the first time, and the remaining 40% is evenly added during the dropping stage. 0.1% antioxidant (BHT) is added during the preparation of the initiator to prevent pre-decomposition.

[0019] Preferably, the dropping temperature is strictly controlled at 40 ± 1 °C and adjusted in real time through the jacket circulating water. The dropping rate is negatively feedback-linked with the temperature of the polymerization kettle. For every 1 °C increase in the kettle temperature, the dropping rate decreases by 2%; for every 1 °C decrease in the kettle temperature, the dropping rate increases by 2%. The monomer conversion rate is monitored in real time during the dropping process to ensure that the conversion rate ≥ 95%.

[0020] Preferably, in the later stage of curing, it is switched to the vacuum curing mode to promote the diffusion of residual monomers. The end point of curing is judged by the viscosity stability, and the viscosity fluctuation is ≤ 5 mPa·s for 3 consecutive hours.

[0021] Preferably, the pH adjustment adopts stepwise addition of alkali. The amount of ammonia water added for the first time is 80% of the theoretical value, and the remaining 20% is added before filtration. The filtration adopts a two-stage filtration system. The first stage: rough filtration with a 0.8 μm ceramic membrane; the second stage: fine filtration with a 0.22 μm polyethersulfone membrane.

[0022] Preferably, if the monomer conversion rate < 90% during the dropping stage, the reaction is immediately terminated and scrapped. If the viscosity drops > 10% during the curing stage, it needs to be reworked and cured again.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] 1. By combining the grafting modification of natural latex with copolymerization, the emulsion has both the high elasticity of natural latex and the durability of synthetic emulsion, while improving the problems of natural latex such as oil resistance, solvent resistance, poor wear resistance, easy aging and yellowing, meeting the needs of high-end protective equipment. By adding additives such as anionic emulsifiers, water-soluble initiators, chain transfer agents and alkaline pH regulators, the emulsion has better stability and processability, and can meet the needs of different application scenarios. Compared with traditional synthetic emulsions, this emulsion uses lower-cost natural latex and synthetic materials, reduces production costs, maintains good performance, and improves economic benefits, so that the synthetic emulsion can take into account the elasticity of natural latex and the durability of synthetic emulsion, low cost and stable process.

[0025] 2. By strictly controlling the reaction conditions, adding additives and optimizing the filtration process, the emulsion has better product quality stability, ensuring the performance consistency of each batch of products and improving product competitiveness. In addition, the emulsion uses a combination of natural latex and synthetic materials, which reduces the impact of traditional synthetic emulsions on the environment during production and use, and realizes green production. DETAILED DESCRIPTION

[0026] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0027] An embodiment provided by the present invention:

[0028] A highly elastic synthetic emulsion obtained by graft modification of natural latex, comprising the following components by dry matter weight percentage: Matrix component: composed of 30% - 32% natural latex and 66% C4 - C5 diolefin mixture, where the natural latex is prepared by centrifugal concentration of fresh latex from Hevea brasiliensis, with a solid content > 60%, protein content < 0.8%, and volatile content < 1.2%; Functional modification component: 2% - 3% acrylate cross - linking monomer, which is a composite system composed of methyl methacrylate and butyl acrylate in a ratio of (1:1) - (1:2); Auxiliary agent system: including 0.2% - 0.4% anionic emulsifier, 0.2% - 0.3% water - soluble initiator, 0.4% chain transfer agent, 0.5% - 1% alkaline pH regulator, and deionized water to make up to 100%; where the C4 - C5 diolefin mixture is a copolymer monomer composed of isoprene and 1,3 - butadiene in a dynamic ratio of (3:7) - (7:3). In the matrix component, the natural latex is selected from fresh latex of Hevea brasiliensis prepared by centrifugal concentration, and the solid content, protein content, and volatile content are strictly controlled to ensure the basic quality. The dynamic ratio of isoprene and 1,3 - butadiene in the C4 - C5 diolefin mixture endows the emulsion with good elasticity and adaptability. In the functional modification component, the composite system of acrylate cross - linking monomers enhances the cross - linking effect of the emulsion. The components of the auxiliary agent system act synergistically. The anionic emulsifier helps to stabilize the emulsion, the water - soluble initiator initiates the polymerization reaction, the chain transfer agent regulates the molecular weight, the alkaline pH regulator maintains the acid - base balance of the system, and deionized water is used as a solvent to make up to 100%, jointly constructing a highly elastic synthetic emulsion with excellent performance.

[0029] Furthermore, the synthesis formula of carboxylated styrene - butadiene latex is

[0030] Latex Example 1 Example 2 Example 3 Example 4 Example 5 Natural latex 300 300 450 360 100 Isoprene 350 450 350 380 650 Butadiene 350 250 200 260 250 Acrylates 3.0 3.0 2.0 2.6 4.6 Mercaptan 0.9 1.0 1.0 1.4 1.2 FeCl2 0 0 1.0 1.2 1.0 Sodium dodecyl sulfate 1.4 2.1 1.7 0 0 Sodium dodecylbenzenesulfonate (30%) 0.8 0.7 0.6 0.6 0.6 Environmentally friendly anionic emulsifier 0 0 0 1.2 1.2 2A1 0 0 0 4.2 4.2 Potassium persulfate 1.0 1.0 1.0 0.5 0.5 Ammonia water 8 8 8 8 10

[0031] The performance indicators of carboxylated styrene - butadiene latex are

[0032]

[0033]

[0034] Grade 1 is good; Grade 3 is poor.

[0035] Furthermore, the anionic emulsifier is branched C12-C14 alkyl alcohol polyoxyethylene ether sulfate or nonylphenol polyoxyethylene ether, which can effectively reduce the surface tension and make the emulsion system more stable; the water-soluble initiator is a redox system composed of potassium persulfate and sodium bisulfite in a ratio of (2:1), and this system can initiate the polymerization reaction under mild conditions, improving the reaction efficiency and controllability; the chain transfer agent is a molecular weight regulation system prepared by compounding dodecyl mercaptan and β-mercaptoethanol in a ratio of (4:1). By precisely controlling the chain growth and chain termination reactions during the polymerization process, the accurate control of the polymer molecular weight is achieved, thereby ensuring the stability and consistency of the emulsion performance and meeting the requirements of different application scenarios.

[0036] A preparation method of a highly elastic synthetic emulsion obtained by graft modification of natural latex, comprising the following steps:

[0037] (1) Pretreatment: Stabilize natural latex with 0.5%-1.0% ammonia water solution and filter it through a 200-mesh sieve.

[0038] (2) Feeding: Add the treated natural latex into a polymerization kettle, and sequentially add deionized water accounting for 50% of the total water volume and all emulsifiers.

[0039] (3) Displacement: Evacuate to -0.85 MPa and maintain for 10 min to complete oxygen displacement.

[0040] (4) Primary polymerization: Add 50% of the total amount of isoprene and butadiene, heat to 20-50 °C and stir for 15 minutes.

[0041] (5) Initiation: Inject 60% of the total amount of the prepared initiator.

[0042] (6) Dropwise polymerization: Mix the remaining 50% of isoprene, butadiene and all crosslinking monomers, and dropwise add them evenly within 6-8 hours, while synchronously adding the remaining 40% of the initiator.

[0043] (7) Aging: React at 50-70 °C for 3-7 hours.

[0044] (8) Post-treatment: Add ammonia water to adjust the pH to 10.0 ± 0.5, and filter and discharge.

[0045] Further, the temperature for ammonia stabilization treatment is 10 - 15°C. This temperature range can effectively inhibit the natural coagulation of latex and ensure the best stabilizing effect of ammonia. The treatment time is 30 - 60 minutes. After filtration through a 200-mesh sieve, the gel content of the latex is ≤0.05%, greatly improving the purity and uniformity of the latex. The pretreated latex is stored in a nitrogen environment to avoid oxidation reactions. When the latex is stored in a nitrogen environment, nitrogen, as an inert gas, can effectively isolate oxygen and prevent the latex from undergoing oxidation reactions, thus maintaining the excellent quality of the latex for a long time and providing a stable and reliable raw material basis for the preparation of the subsequent synthetic emulsion.

[0046] Further, before vacuum replacement, the polymerization kettle needs to be evacuated three times in a cycle. Each time, it is evacuated to -0.85 MPa and maintained for 5 minutes. Such an operation can fully remove the air and impurities in the kettle. After replacement, nitrogen is filled to atmospheric pressure, and this is repeated three times to completely remove oxygen. The residual oxygen concentration is ≤10 ppm, providing an oxygen-free and pure ideal environment for the subsequent polymerization reaction and effectively ensuring the smooth progress of the reaction and the stability of the product quality.

[0047] Further, the initiator solution is pre-cooled to below 5°C in an ice-water bath and added in two portions. 60% of the total amount of the initiator is added for the first time, and the remaining 40% is evenly added during the dropping stage. 0.1% antioxidant (BHT) is added during the preparation of the initiator to prevent pre-decomposition. This operation can quickly initiate a certain degree of reaction at the initial stage of the polymerization reaction, laying the foundation for the reaction. The remaining 40% is evenly added during the dropping stage to ensure the continuous and stable progress of the reaction and maintain the rate and process of the polymerization reaction. At the same time, 0.1% antioxidant (BHT) is added during the preparation of the initiator, which can effectively prevent the pre-decomposition of the initiator during pre-cooling and storage, ensuring the activity and stability of the initiator, thereby ensuring the smooth progress of the entire polymerization reaction according to the set conditions and improving the controllability and stability of the product quality.

[0048] Further, the dropping temperature is strictly controlled at 40 ± 1°C and adjusted in real time through the jacket circulating water. The dropping rate is negatively feedback-linked with the temperature of the polymerization kettle. For every 1°C increase in the kettle temperature, the dropping rate decreases by 2%; for every 1°C decrease in the kettle temperature, the dropping rate increases by 2%. This ensures that the reaction system is always in a stable state. The monomer conversion rate is monitored in real time during the dropping process to ensure that the conversion rate ≥95%, thereby effectively improving the product quality.

[0049] Further, in the later stage of curing, switch to the vacuum curing mode in a timely manner to promote the more efficient diffusion of residual monomers through the vacuum environment, thereby further optimizing the product performance. The determination of the curing end point is based on the viscosity stability as the key criterion. The specific requirement is that the viscosity fluctuation is ≤5 mPa·s for 3 consecutive hours. Through this precise determination method, the curing process can be accurately grasped to ensure that the product quality reaches a highly stable state and meets high standards.

[0050] Furthermore, the pH is adjusted by a staged alkali addition method. The amount of ammonia water added for the first time is set at 80% of the theoretical value to initially create a suitable pH environment for the reaction system. The remaining 20% is added before filtration to accurately fine-tune the pH value and ensure that the final product reaches an ideal acid-base balance. The filtration process adopts a two-stage filtration system. The first stage is a 0.8μm ceramic membrane coarse filtration, which can effectively intercept larger particle impurities. The second stage is a 0.22μm polyethersulfone membrane fine filtration to further remove tiny impurities and achieve fine purification of the product. This unique pH adjustment and filtration method has built a more complete, sophisticated and innovative process path for the patented technology, significantly improving the quality and stability of the product.

[0051] Furthermore, during the addition phase, if the monomer conversion rate is monitored to be less than 90%, the reaction must be terminated immediately and the product must be scrapped to prevent unqualified intermediates from entering the next stage. During the maturation phase, if the viscosity drops by more than 10%, it indicates that the product quality does not meet the standard and must be reprocessed and re-maturized to ensure that each batch of product meets strict quality requirements. This clear and strict process control standard provides a strong quality assurance system for the patented technology, significantly improving the product's stability and reliability and giving it a competitive advantage in the market.

[0052] Working principle: Fresh Hevea rubber tree latex is centrifuged and concentrated to obtain natural latex with a solid content greater than 60%, a protein content less than 0.8%, and a volatile matter content less than 1.2%. Then, this natural latex is copolymerized with synthetic materials such as isoprene and 1,3-butadiene to form a graft copolymer with high elasticity and durability. At the same time, by adding an appropriate amount of acrylic ester cross-linking monomers, such as a composite system of methyl methacrylate and butyl acrylate, the cross-linking degree and oil and solvent resistance of the emulsion are further improved. In addition, auxiliary agents such as anionic emulsifiers, water-soluble initiators, chain transfer agents and alkaline pH regulators are also added to improve the stability, processability and reaction rate of the emulsion. In the copolymerization process, natural latex is first mixed with isoprene, butadiene and a cross-linking monomer, and then replaced in a polymerization kettle to exclude oxygen and impurities to create a pure reaction environment. The polymerization reaction is then initiated by injecting an initiator and dropwise polymerization is carried out at a certain temperature, so that the remaining isoprene, butadiene and cross-linking monomer are gradually added, and the remaining initiator is added at the same time. After the polymerization reaction is completed, a aging process is carried out to further improve the stability and performance of the emulsion. Finally, the pH value is adjusted by adding ammonia and filtered through a two-stage filtration system to obtain a final high-elasticity synthetic emulsion product. By combining the graft modification of natural latex with copolymerization, the problems of natural latex such as oil resistance, solvent resistance, poor wear resistance, and easy aging and yellowing are effectively solved, while the stability and processability of the emulsion are improved, and a modified emulsion that takes into account both elasticity and durability is achieved.

[0053] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above-described exemplary embodiments, and without departing from the spirit or essential characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A highly elastic synthetic emulsion obtained by graft modification of natural latex, characterized in that, Comprising the following components by weight percentage of dry matter: Matrix component: composed of 30% - 32% natural latex and 66% C4 - C5 diolefin mixture, wherein the natural latex is obtained by centrifugal concentration of fresh latex from Hevea brasiliensis, with a solid content > 60%, protein content < 0.8%, and volatile content < 1.2%; Functional modification component: 2% - 3% acrylate cross - linking monomer, which monomer contains a composite system composed of methyl methacrylate and butyl acrylate in a ratio of (1:1) - (1:2); Auxiliary agent system: including 0.2% - 0.4% anionic emulsifier, 0.2% - 0.3% water - soluble initiator, 0.4% chain transfer agent, 0.5% - 1% alkaline pH regulator, and deionized water to make up to 100%; wherein the C4 - C5 diolefin mixture is a copolymer monomer composed of isoprene and 1,3 - butadiene in a dynamic ratio of (3:7) - (7:3).

2. The highly elastic synthetic emulsion obtained by graft modification of natural latex according to claim 1, characterized in that: The anionic emulsifier is branched C12 - C14 alkyl alcohol polyoxyethylene ether sodium sulfate or nonylphenol polyoxyethylene ether; the water - soluble initiator is a redox system composed of potassium persulfate and sodium bisulfite in a ratio of (2:1); the chain transfer agent is a molecular weight regulation system composed of dodecyl mercaptan and β - mercaptoethanol in a ratio of (4:1).

3. A method for preparing a highly elastic synthetic emulsion obtained by graft-modifying natural latex according to claims 1-2, characterized in that, Including the following steps: (1) Pretreatment: Stabilize the natural latex with 0.5% - 1.0% ammonia water solution and filter through a 200 - mesh sieve. (2) Feeding: Add the treated natural latex into the polymerization kettle, and successively add 50% of the total amount of deionized water and all the emulsifiers. (3) Replacement: Evacuate to - 0.85 MPa and maintain for 10 min to complete oxygen replacement. (4) Primary polymerization: Add 50% of the total amount of isoprene and butadiene, heat up to 20 - 50 °C and stir for 15 minutes. (5) Initiation: Inject 60% of the total amount of the prepared initiator. (6) Drop - wise polymerization: Mix the remaining 50% isoprene, butadiene and all the cross - linking monomers, and drop - wise add them evenly within 6 - 8 hours, and simultaneously supplement the remaining 40% initiator. (7) Aging: React at 50 - 70 °C for 3 - 7 hours. (8) Post - treatment: Add ammonia water to adjust the pH to 10.0 ± 0.5, and filter and discharge.

4. The preparation method of the highly elastic synthetic emulsion obtained by graft modification of natural latex according to claim 3, characterized in that: The temperature of the ammonia water stabilization treatment is 10 - 15 °C, the treatment time is 30 - 60 minutes, the gel content of the latex after filtering through a 200 - mesh sieve ≤ 0.05%, and the pretreated latex is stored in a nitrogen environment to avoid oxidation reaction.

5. The preparation method of the highly elastic synthetic emulsion obtained by graft modification of natural latex according to claim 3, characterized in that: Before the vacuum replacement, the polymerization kettle needs to be evacuated three times in a cycle. Each time it is evacuated to - 0.85 MPa and maintained for 5 minutes. After the replacement is completed, nitrogen is filled to atmospheric pressure, and this is repeated three times to completely remove oxygen, and the residual oxygen concentration ≤ 10 ppm.

6. The preparation method of the highly elastic synthetic emulsion obtained by graft modification of natural latex according to claim 3, characterized in that: The initiator solution is pre - cooled to below 5 °C by an ice - water bath and added in two times. 60% of the total amount of the initiator is added for the first time, and the remaining 40% is evenly supplemented during the drop - wise addition stage. 0.1% antioxidant (BHT) is added during the preparation of the initiator to prevent pre - decomposition.

7. The preparation method of the highly elastic synthetic emulsion obtained by graft modification of natural latex according to claim 3, characterized in that: The dropping temperature is strictly controlled at 40 ± 1 °C and adjusted in real time through the jacket circulating water. The dropping rate is negatively feedback-linked with the temperature of the polymerization kettle. For every 1 °C increase in the kettle temperature, the dropping rate decreases by 2%, and for every 1 °C decrease in the kettle temperature, the dropping rate increases by 2%. The monomer conversion rate is monitored in real time during the dropping process to ensure that the conversion rate ≥ 95%.

8. The preparation method of the highly elastic synthetic emulsion modified by grafting natural latex according to claim 3, characterized in that: In the later stage of curing, it is switched to the vacuum curing mode to promote the diffusion of residual monomers. The curing end point is judged by the viscosity stability, and the viscosity fluctuation ≤ 5 mPa·s for 3 consecutive hours.

9. The preparation method of the highly elastic synthetic emulsion obtained by graft modification of natural latex according to claim 3, characterized in that: The pH adjustment adopts staged addition of alkali. The first addition of ammonia water is 80% of the theoretical value, and the remaining 20% is added before filtration. The filtration adopts a two-stage filtration system. The first stage: rough filtration with a 0.8 μm ceramic membrane, and the second stage: fine filtration with a 0.22 μm polyethersulfone membrane.

10. A preparation formula and method for a highly elastic synthetic emulsion grafted with natural latex according to claim 9, characterized in that: If the monomer conversion rate < 90% during the dropping stage, the reaction is immediately terminated and scrapped. If the viscosity drops > 10% during the curing stage, it needs to be reworked and cured again.

Images