Preparation method of carboxyl nitrile butadiene latex for medical gloves

Abstract

The application provides a preparation method of carboxyl butyronitrile latex for medical gloves, which comprises the following steps: mixing desalted water, an emulsifier, a dispersing agent, a molecular weight regulator, an activator, a reducing agent, an electrolyte, methacrylic acid and acrylonitrile, adding an oxygen scavenger and butadiene, controlling the temperature to 5-8 DEG C, then adding an initiator and performing polymerization at 5-8 DEG C, when the polymerization conversion rate reaches 30%-60%, supplementing the desalted water, acrylonitrile and methacrylic acid, and when the polymerization conversion rate is greater than 98%, the carboxyl butyronitrile latex for medical gloves is obtained; wherein the emulsifier is a mixture of an anionic emulsifier and a cationic emulsifier, the anionic emulsifier is sodium dodecyl sulfate, and the cationic emulsifier is a sugar-based gemini cationic surfactant; and the activator is a mixture of ferrous sulfate and an EDTA salt. The product prepared by the method has low gel content, excellent film forming property, mechanical stability and strength.

Description

Technical Field

[0001] This invention relates to the field of latex preparation technology, and specifically to a method for preparing carboxylated butadiene nitrile latex for medical gloves. Background Technology

[0002] Carboxylated nitrile butadiene latex, abbreviated as XNBRL, is a milky white liquid. Due to the introduction of highly polar carboxyl groups into its macromolecular chain, its activity and adhesive strength are improved, resulting in superior performance compared to ordinary nitrile butadiene latex. However, existing production processes for carboxylated nitrile butadiene latex all employ medium-to-high temperature methods, and the resulting latex products generally suffer from high gel content, low strength, poor film-forming properties, or are unsuitable for industrial production.

[0003] For example, Chinese patent document CN201310448254.5 discloses a method for preparing carboxylated nitrile latex for impregnating industrial and medical examination gloves. The method comprises, by mass percentage, 110-140 parts deionized water, 2.5-4.0 parts emulsifier (selected from one or more of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, nonylphenol polyoxyethylene ether-10, alkylphenol polyoxyethylene ether-12, and dispersant N), 0.1-0.5 parts electrolyte, 0.1-0.5 parts pH buffer, 0.5-1.5 parts thiol, 28-35 parts acrylonitrile, 2-7 parts unsaturated carboxylic acid, 2-5 parts unsaturated carboxylic acid ester, and 0.1-2 parts unsaturated crosslinking agent. The monomer and 0.2–0.5 parts of initiator are added sequentially to the polymerization reactor, and the reactor is purged with nitrogen and evacuated three times. Then, 60–70 parts of butadiene are added, and the temperature is raised to 25–35°C. The polymerization reaction is carried out for 6–8 hours. Then, 1.0–1.5 parts of unsaturated carboxylic acid, 0.8–1.0 parts of unsaturated carboxylic acid ester, 0.1–0.3 parts of emulsifier, and 0.2–0.4 parts of thiol are added for the first time. The temperature is then raised to 35–40°C, and the polymerization reaction is carried out for 4–6 hours. Then, 0.8–1.5 parts of unsaturated carboxylic acid, 0.4–0.7 parts of unsaturated carboxylic acid ester, 0.1–0.3 parts of emulsifier, and 0.2–0.4 parts of thiol are added for the second time, along with 0.02–0.2 parts of reducing agent. Finally, the temperature is raised to 40–50°C, and the polymerization reaction is carried out for 4–6 hours. When the conversion rate reaches over 98%, a terminator is added to stop the polymerization reaction, resulting in a carboxylated nitrile butadiene latex with a solid content of 43%–45%. The drawbacks or shortcomings of this technical solution are: it uses a high-temperature polymerization method with segmented temperature control, making operation complex and industrial implementation difficult.

[0004] Chinese patent document CN200510029573.8 discloses a method for preparing carboxylated nitrile butadiene latex, specifically: adding 85-140 parts by weight of demineralized water, 1.5-3.5 parts by weight of emulsifier, 0.3-1.5 parts by weight of molecular chain regulator, and 0.1-0.5 parts by weight of pH buffer; then adding 50-75 parts by weight of butadiene monomer, 20-45 parts by weight of acrylonitrile, 1-10 parts by weight of unsaturated carboxylic acid, and 1-5 parts by weight of unsaturated carboxylic acid ester; finally adding 0.1-1.0 parts by weight of regulator; the first-stage reaction temperature is 5-9℃. After reacting for 4 hours, 5-15% (by weight of the first emulsifier) ​​of the emulsifier supplement solution is added, and the reaction continues for 12 hours. Then, 3-7% (by weight of the first supplemented emulsifier) ​​of the second supplemented emulsifier and reducing agent are added, and the reaction continues for 8 hours. The reaction is stopped when the conversion rate reaches 90%. The resulting carboxylated nitrile latex has the following properties: solid content 44.0-46.0%, viscosity ≤100 mPa·s, surface tension ≤50 mN / m, particle size 120-160 nm, mechanical stability ≥99.7%, and gel content ≤40.0%. The product exhibits strong adhesion to lining fabrics and hanging fabrics. The drawbacks or shortcomings of this technical solution are: low conversion rate, high residual monomer content, resulting in high gel content.

[0005] Chinese patent document CN201510971937.8 discloses a method for preparing carboxylated nitrile latex for high-strength, high-abrasion-resistant nitrile gloves. The method involves adding, by weight, the following components: acrylonitrile: 28-35 parts; butadiene: 60-70 parts; unsaturated carboxylic acid: 2-7 parts; unsaturated carboxylic acid ester: 0-5 parts; reactive emulsifier: 2.5-5.0 parts; electrolyte: 0.1-0.5 parts; pH buffer: 0.1-0.5 parts; thiol: 0.5-1.5 parts; initiator: 0.2-0.5 parts; and deionized water: 110-140 parts. A segmented temperature-controlled process is employed. Initially, the temperature is raised to 25–35°C, and the reaction is continued for 6–8 hours. The first addition of reactive emulsifier and thiol is then made. The temperature continues to rise to 36–40°C, and the reaction is continued for 4–6 hours. A second addition of reactive emulsifier and thiol is then made. Finally, the temperature is raised to 45–60°C, and the reaction is continued for 4–6 hours. When the conversion rate reaches 98%, the reaction is stopped, yielding carboxylated nitrile butadiene latex with a solid content of 43%–45%. The drawbacks of this technique are that it employs a medium-to-high temperature polymerization method with segmented temperature control, making operation complex and difficult to control, which is not conducive to industrial production.

[0006] Chinese patent document CN201310699808.9 discloses a method for producing carboxylated nitrile butadiene latex. The method involves polymerizing a monomer with an anionic emulsifier and a nonionic emulsifier at 50–75°C for 6–8 hours. The anionic emulsifier is one or more compounds selected from sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, and sodium dodecyl aryl ether sulfonate. The nonionic emulsifier is one or more compounds selected from nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether, wherein the number of ethylene oxide adducts in the nonylphenol polyoxyethylene ether and octylphenol polyoxyethylene ether is no more than 10. The resulting carboxylated nitrile butadiene latex has the following properties: solid content of 44.0–46.0%, viscosity ≤100 mPa·s, and particle size of 110–140 nm. The drawback of this method is that it uses a high-temperature polymerization process, resulting in high branching and cross-linking of the product, leading to a high gel content.

[0007] Chinese patent document CN201510679217.4 discloses a method for preparing high-performance carboxylated nitrile butadiene latex: This latex employs an emulsion polymerization process using styrene-butadiene latex as a seed, with partial monomer addition. Butadiene and acrylonitrile are the main monomers, unsaturated carboxylic acids are used, supplemented with functional monomers such as multi-double-bond crosslinking monomers. A composite emulsification system is used during polymerization, consisting of a combination of reactive and anionic emulsifiers. Persulfate is used as an initiator, alkyl thiols as molecular weight regulators, and other additives. The reaction temperature is 40–60℃, and the conversion rate is over 98%. During the latex production process, the raw materials are dispersed using an ultrasonic homogenizer or high-pressure homogenizer to form a stable fine emulsion of 50–500 nm, which is then added dropwise to the reaction vessel. The final prepared carboxylated nitrile butadiene latex has a particle size of 100–120 nm, good fluidity, moderate viscosity, excellent mechanical and chemical stability, and high toughness and bonding strength. The shortcomings or deficiencies of this technical solution are: the method uses high-temperature polymerization and a continuous dripping process, which makes it difficult to achieve industrial production.

[0008] Chinese patent document CN202110983592.3 discloses a carboxylated nitrile latex for gloves and its preparation method. The raw materials, by mass parts, include 80-100 parts deionized water, 1-3 parts molecular weight regulator, 0.2-0.4 parts pH buffer, 2-6 parts emulsifier, 40-60 parts butadiene, 15-40 parts acrylonitrile, 10-20 parts functional monomer, 2-5 parts unsaturated carboxylic acid, 0.3-1.5 parts initiator, and 0.4-0.5 parts auxiliaries. Six parts; the functional monomers include ethylene glycol diacrylate, diallyl maleate, and isopropyl acetate in a mass ratio of 1:(1-1.2):(0.5-1), and the emulsifiers include sodium dodecylbenzenesulfonate, ethylene oxide lauryl alcohol, and propylene glycol monostearate in a mass ratio of (1-2):(0.5-1.2):(1-2). The polymerization reaction temperature is 65-70℃, and the resulting carboxylated nitrile latex exhibits excellent chemical and mechanical stability. The drawback of this technical solution is that the method uses a high-temperature polymerization method, resulting in medical gloves with poor strength.

[0009] Chinese patent document CN202111626575.0 discloses a method for preparing a semi-interpenetrating network structure carboxylated nitrile butadiene latex. The method involves adding the carboxylated nitrile butadiene latex to a reaction vessel, stirring at room temperature, then adding pure water and sodium dodecylbenzenesulfonate for pre-emulsification for 30 minutes. After 30 minutes, 320–370 g of acrylonitrile and 10–50 g of divinylbenzene are added. The mixture is then subjected to a vacuum-nitrogen purging process repeated three times, maintaining a negative pressure of 560 mmHg. Immediately afterwards, 630–680 g of butadiene is added. 7 g of ammonium persulfate is added to initiate polymerization, maintaining the polymerization temperature at 50–60°C for 7–8 hours to obtain the semi-interpenetrating network structure carboxylated nitrile butadiene latex. Products made from this latex exhibit a tensile strength of 18.3 MPa and an elongation at break of 493%, making it suitable for applications in medical gloves, dipped gloves, and abrasion-resistant products. The defect or deficiency of this technical solution is that the use of graft polymerization to prepare a semi-interpenetrating network structure of carboxylated butadiene nitrile latex results in poor film-forming properties. Summary of the Invention

[0010] The technical problem to be solved by the present invention is to provide a method for preparing carboxylated nitrile butadiene latex for medical gloves, so as to solve the problems of high gel content, low strength, poor film-forming properties, or unfavorable conditions for industrial production in the existing carboxylated nitrile butadiene latex used to prepare medical gloves.

[0011] Therefore, the present invention provides the following technical solution:

[0012] A method for preparing carboxylated butadiene nitrile latex for medical gloves includes the following steps:

[0013] (1) Mix deionized water, emulsifier, dispersant, molecular weight regulator, activator, reducing agent, electrolyte, methacrylic acid and acrylonitrile, add oxygen scavenger and butadiene to obtain a mixture;

[0014] (2) After controlling the temperature of the mixture to 5-8°C, an initiator is added and a polymerization reaction is carried out at 5-8°C. When the polymerization conversion rate reaches 30%-60%, demineralized water, acrylonitrile and methacrylic acid are added. When the polymerization conversion rate is greater than 98%, the material is discharged to obtain the carboxylated butadiene nitrile latex for medical gloves.

[0015] The emulsifier is a mixture of anionic and cationic emulsifiers, wherein the anionic emulsifier is sodium dodecyl sulfate and the cationic emulsifier is a glycosyl gemini cationic surfactant.

[0016] The activator is a mixture of ferrous sulfate and EDTA salt.

[0017] Regarding the raw material components of the carboxylated nitrile latex in this invention, the inventors discovered through research that controlling the polymerization reaction temperature to 5–8°C is beneficial for controlling the latex stability and gel content.

[0018] Optionally, when the polymerization conversion rate reaches 30% to 35%, adding demineralized water can further adjust the latex viscosity of the polymerization system; when the polymerization conversion rate reaches 55% to 60%, adding acrylonitrile and methacrylic acid monomers can increase the monomer concentration in the later stage of the polymerization reaction, enabling the polymerization reaction to achieve a high conversion rate of over 98%.

[0019] Optionally, the carboxylated nitrile latex for medical gloves comprises, by weight, the following raw materials: 64-70 parts butadiene, 28-38 parts acrylonitrile, 3.5-8.0 parts methacrylic acid, 2.5-4.0 parts emulsifier, 1.0-3.0 parts dispersant, 0.02-0.08 parts electrolyte, 0.005-0.05 parts activator, 0.02-0.06 parts reducing agent, 0.4-1.0 parts molecular weight regulator, 0.005-0.02 parts oxygen scavenger, 0.04-0.10 parts initiator, and 113-135 parts desalinated water.

[0020] Optionally, in step (2), 3 to 5 parts of deionized water, 2 to 5 parts of acrylonitrile, and 0.5 to 2 parts of methacrylic acid are added by weight.

[0021] Optionally, the structural formula of the glycosyl gemini cationic surfactant is as follows:

[0022]

[0023] Where n = 1 to 3, and R is an alkyl group.

[0024] Optionally, R is selected from C12 to C14 straight-chain alkyl groups.

[0025] Traditional quaternary ammonium salt cationic surfactants are highly irritating. When combined with anionic surfactants, they precipitate due to interactions, thus losing their effectiveness and becoming unusable. In contrast, glycosyl gemini cationic surfactants, by introducing glycosyl groups into traditional cationic surfactants, reduce their irritation and allow them to be well-combined with anionic surfactants. These interactions form a composite with higher surface activity, reducing the critical micelle concentration and surface tension of the emulsifier. This facilitates the entry of monomers into the polymerization site—the solubilized micelles—resulting in larger latex particles with a wider particle size distribution. Smaller particles can fill the gaps between larger particles, increasing the latex particle packing volume and producing high-solids-content carboxylated nitrile latex. This improves the mechanical stability of the latex, and the particle size of carboxylated nitrile latex can reach over 120 nm.

[0026] Optionally, the mass ratio of the anionic emulsifier to the cationic emulsifier in the emulsifier is 1:0.05 to 0.1.

[0027] Optionally, the mass ratio of ferrous sulfate to EDTA salt in the activator is 1:(0.9-1.1).

[0028] Optionally, the EDTA salt is EDTA-sodium iron salt.

[0029] When using ferrous sulfate alone as an activator, the polymerization reaction is too fast and the latex stability is poor; when using EDTA-sodium iron salt alone as an activator, the polymerization reaction rate is too slow, which is not conducive to industrial production efficiency. By using a specific ratio of ferrous sulfate and EDTA-sodium iron salt to compound the reaction, the polymerization reaction rate can be steadily controlled, which is beneficial for heat dissipation, improves the stability of the latex, and results in high production efficiency, which is conducive to industrial production.

[0030] Optionally, the initiator is a low-temperature redox initiator, preferably cumene hydroperoxide and / or dicumene hydroperoxide.

[0031] Optionally, the electrolyte is any one of sodium carbonate, sodium bicarbonate, and sodium pyrophosphate.

[0032] The dispersant, reducing agent, molecular weight regulator, and oxygen scavenger described in this invention can all be selected from those known in the art and are not particularly limited. For example, the dispersant can be selected from at least one of sodium disulfite, dimethyl ketoxime, isoascorbic acid, carbazide, and N-isopropylhydroxylamine. The reducing agent can be selected from dichlorophenoxylate, etc., and the molecular weight regulator is a commonly used regulator in emulsion polymerization, such as tert-dodecyl mercaptan, n-dodecyl mercaptan, etc. The oxygen scavenger can be selected from at least one of sodium dithionite, dimethyl ketoxime, isoascorbic acid, carbazide, and N-isopropylhydroxylamine.

[0033] The carboxylated butadiene nitrile latex for medical gloves prepared using the method of this invention has excellent film-forming properties, good mechanical stability, high strength, and produces gloves with good performance. Furthermore, the method is simple to operate and easy to apply industrially.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. The method for preparing carboxylated nitrile butadiene latex for medical gloves provided by this invention utilizes a low-temperature emulsion polymerization method. During polymerization, a specific glycosyl gemini cationic surfactant and anionic surfactant are combined to form an emulsifier, breaking the traditional limitation that anionic and cationic surfactants cannot be used together. The combined emulsifier further reduces the critical micelle concentration and surface tension of the solution, thereby improving emulsification efficiency. By using a specific ratio of ferrous sulfate and EDTA-iron sodium salt, the polymerization reaction rate can be stably controlled, improving the stability of the latex and resulting in high production efficiency. Simultaneously, by employing a process of adding demineralized water and monomers in batches at different polymerization stages, a linear carboxylated nitrile butadiene latex is synthesized, with a solid content of 44.0%–46.0%, viscosity ≤100 mPa·S, particle size 120–150 nm, mechanical stability ≤0.1%, and gel content <5.0%. Not only does it have low gel content, but it also possesses excellent film-forming properties, mechanical stability, and strength. Furthermore, the preparation method is simple and controllable, making it easy for industrial production.

[0036] 2. The solid content of nitrile butadiene latex is typically 25%–30%. For work gloves, the solid content of carboxylated nitrile butadiene latex is usually required to be above 40%, while for medical-grade carboxylated nitrile butadiene latex, it is usually required to be above 44%. To increase the solid content of the latex, the polymerization reaction must be carried out under conditions of low water ratio and high conversion rate. A lower water ratio inevitably affects the viscosity and pH of the system, while a higher conversion rate leads to a significant increase in gel content in the later stages of the reaction. Especially when the solid content reaches a certain level, the system viscosity increases, the latex easily becomes a paste, and it loses its fluidity. The inventors have discovered that the carboxylated nitrile butadiene latex composed of specific components in this invention, combined with the above preparation method, can significantly reduce the viscosity of the system during the preparation process. Furthermore, the resulting carboxylated nitrile butadiene latex not only has a high solid content and a wide particle size distribution but also a low gel content, which can meet the application requirements of medical gloves. Detailed Implementation

[0037] The present invention will now be described in detail through embodiments. It should be noted that the following embodiments are only for further illustration of the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0038] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0039] Evaluation and analysis methods:

[0040] Total solids content: Complies with standard SH / T 1154-2011

[0041] Latex viscosity: Complies with standard SH / T 1152-2014

[0042] pH value: Complies with standard SH / T 1150-2011

[0043] Mechanical stability: Complies with standard SH / T 1151-2011

[0044] Surface tension: Complies with standard SH / T 1156-2014

[0045] Raw gum gel content: Complies with standard SH / T 1050-91

[0046] Commercially available dispersants, reducing agents, molecular weight regulators, and oxygen scavengers, as well as commercially available or self-made glycosyl gemini cationic surfactants, can all meet the technical requirements of this invention. However, for ease of comparison, the following examples and comparative examples all use raw materials purchased from the following manufacturers:

[0047] Butadiene: Complies with GB / T 13291-2008 standard, industrial grade, purity ≥99.5%, Lanzhou Petrochemical Company;

[0048] Acrylonitrile: Complies with GB / T 7717.1-2008 standard, industrial grade, purity ≥99.5%, Lanzhou Petrochemical Company;

[0049] Methacrylic acid, industrial grade, purity >99%, Sinopharm Chemical Reagent Co., Ltd.

[0050] Glycosyl gemini cationic surfactants with different carbon numbers and different degrees of polymerization of glycosyl groups, analytical grade, purity > 99%, Sinopharm Chemical Reagent Co., Ltd.

[0051] Sodium dodecyl sulfate, industrial grade, purity >96%, Lanzhou Petrochemical Company;

[0052] Ferrous sulfate, industrial grade, purity ≥98%, Lanzhou Petrochemical Company;

[0053] Diao Bai Kuai: Industrial product, purity ≥98%, Lanzhou Petrochemical Company;

[0054] Ethylenediaminetetraacetic acid (EDTA-sodium iron), industrial grade, purity (EDTA on dry basis) ≥97.0%, Lanzhou Petrochemical Company;

[0055] Tert-dodecyl mercaptan, imported industrial product, purity ≥97.3%, Lanzhou Petrochemical Company;

[0056] Diisopropylbenzene hydrogen peroxide, industrial grade, purity ≥80%, Lanzhou Petrochemical Company;

[0057] Oxygen scavenger, industrial grade, Na2S2O4 content ≥85.0%, Lanzhou Petrochemical Company.

[0058] Example 1

[0059] 116 parts of demineralized water, 3 parts of sodium dodecyl sulfate, 0.15 parts of C12-glycosyl gemini cationic surfactant (n=2), 1.5 parts of dispersant NF, 0.03 parts of sodium carbonate, 0.005 parts of ferrous sulfate, 0.005 parts of EDTA-sodium iron salt, 0.04 parts of bleaching agent, 0.5 parts of tert-dodecyl mercaptan, 27 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 70 parts of butadiene were then added, and the polymerization reactor was ready. When the temperature drops below 8℃, 0.06 parts of diisopropylbenzene hydrogen peroxide are added to start the polymerization reaction. During the process, the polymerization reaction temperature is controlled at 5-8℃. The dry matter is measured every 2 hours. When the polymerization conversion rate reaches 35%, 3 parts of deionized water are added to continue the reaction. When the polymerization conversion rate reaches 56%, 3 parts of acrylonitrile and 1 part of methacrylic acid are added. When the conversion rate reaches 98.4%, the material is discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests are performed. The results are shown in Table 1.

[0060] Example 2

[0061] 120 parts of demineralized water, 3 parts of sodium dodecyl sulfate, 0.3 parts of C13-glycosyl gemini cationic surfactant (n=1), 2.0 parts of dispersant NF, 0.04 parts of sodium bicarbonate, 0.005 parts of ferrous sulfate, 0.005 parts of EDTA-sodium iron salt, 0.03 parts of bleach, 0.55 parts of tert-dodecyl mercaptan, 32 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 65 parts of butadiene were then added, and the polymerization reactor was ready. When the temperature drops below 8℃, 0.06 parts of diisopropylbenzene hydrogen peroxide are added to start the polymerization reaction. During the process, the polymerization reaction temperature is controlled at 5-8℃. The dry matter is measured every 2 hours. When the polymerization conversion rate reaches 32%, 5 parts of deionized water are added to continue the reaction. When the polymerization conversion rate reaches 60%, 2 parts of acrylonitrile and 1 part of methacrylic acid are added. When the conversion rate reaches 98.2%, the material is discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests are performed. The results are shown in Table 1.

[0062] Example 3

[0063] 126 parts of demineralized water, 3.2 parts of sodium dodecyl sulfate, 0.2 parts of C12-glycosyl gemini cationic surfactant (n=3), 2.5 parts of dispersant NF, 0.05 parts of sodium carbonate, 0.008 parts of ferrous sulfate, 0.008 parts of EDTA-sodium iron salt, 0.02 parts of bleach, 0.5 parts of tert-dodecyl mercaptan, 29 parts of acrylonitrile, and 5.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. Then, 66 parts of butadiene were added, and polymerization was carried out. When the temperature of the reactor drops below 8°C, 0.1 parts of cumene hydroperoxide are added to start the polymerization reaction. During the process, the polymerization reaction temperature is controlled between 5 and 8°C. The dry matter content is measured every 2 hours. When the polymerization conversion rate reaches 33%, 4 parts of deionized water are added to continue the reaction. When the polymerization conversion rate reaches 57%, 3 parts of acrylonitrile and 2 parts of methacrylic acid are added. When the conversion rate reaches 98.1%, the material is discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests are performed. The results are shown in Table 1.

[0064] Example 4

[0065] 130 parts of demineralized water, 3.6 parts of sodium dodecyl sulfate, 0.3 parts of C14-glycosyl gemini cationic surfactant (n=2), 2.0 parts of dispersant NF, 0.05 parts of sodium carbonate, 0.01 parts of ferrous sulfate, 0.01 parts of EDTA-sodium iron salt, 0.06 parts of bleaching agent, 0.6 parts of tert-dodecyl mercaptan, 26 parts of acrylonitrile, and 6.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. Then, 68 parts of butadiene were added, and the polymerization reactor was allowed to heat up. When the temperature drops below 8°C, 0.08 parts of cumene hydroperoxide are added to start the polymerization reaction. During the process, the polymerization reaction temperature is controlled at 5-8°C. The dry matter is measured every 2 hours. When the polymerization conversion rate reaches 30%, 3 parts of deionized water are added to continue the reaction. When the polymerization conversion rate reaches 55%, 5 parts of acrylonitrile and 0.5 parts of methacrylic acid are added. When the conversion rate reaches 98.7%, the material is discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests are performed. The results are shown in Table 1.

[0066] Example 5

[0067] 110 parts of demineralized water, 2.5 parts of sodium dodecyl sulfate, 0.15 parts of C13-glycosyl gemini cationic surfactant (n=1), 2.8 parts of dispersant NF, 0.06 parts of sodium pyrophosphate, 0.01 parts of ferrous sulfate, 0.01 parts of EDTA-sodium iron salt, 0.05 parts of bleach, 0.8 parts of tert-dodecyl mercaptan, 33 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. Then, 64 parts of butadiene were added. The polymerization reactor was then ready for use. When the temperature drops below 8℃, 0.05 parts of diisopropylbenzene hydrogen peroxide are added to start the polymerization reaction. During the process, the polymerization reaction temperature is controlled at 5-8℃. The dry matter is measured every 2 hours. When the polymerization conversion rate reaches 34%, 5 parts of deionized water are added to continue the reaction. When the polymerization conversion rate reaches 59%, 2 parts of acrylonitrile and 2 parts of methacrylic acid are added. When the conversion rate reaches 98.5%, the material is discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests are performed. The results are shown in Table 1.

[0068] Comparative Example 1

[0069] 116 parts of demineralized water, 3 parts of sodium dodecyl sulfate, 1.5 parts of dispersant NF, 0.03 parts of sodium carbonate, 0.005 parts of ferrous sulfate, 0.005 parts of EDTA-sodium iron salt, 0.04 parts of bleach, 0.5 parts of tert-dodecyl mercaptan, 27 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 70 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 8°C, 0. 0.6 parts of diisopropylbenzene hydrogen peroxide were used to start the polymerization reaction. During the process, the polymerization reaction temperature was controlled at 5-8℃. The dry matter was measured every 2 hours. When the polymerization conversion rate reached 35%, 3 parts of deionized water were added and the reaction continued. When the polymerization conversion rate reached 56%, 3 parts of acrylonitrile and 1 part of methacrylic acid were added. When the conversion rate reached 90.4%, the material was discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adding alkali solution to adjust the pH of the carboxylated nitrile butadiene latex for medical gloves, physical property tests were conducted. The results are shown in Table 1.

[0070] Comparative Example 2

[0071] 120 parts of demineralized water, 3 parts of sodium dodecyl sulfate, 0.3 parts of C13-glycosyl gemini cationic surfactant (n=1), 2.0 parts of dispersant NF, 0.04 parts of sodium bicarbonate, 0.01 parts of ferrous sulfate, 0.03 parts of bleach, 0.55 parts of tert-dodecyl mercaptan, 32 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. Then, 65 parts of butadiene were added. The polymerization reactor temperature was allowed to drop below 8°C. Add 0.06 parts of diisopropylbenzene hydrogen peroxide to start the polymerization reaction. During the process, control the polymerization reaction temperature at 5-8℃. Measure the dry matter every 2 hours. When the polymerization conversion rate reaches 32%, add 5 parts of deionized water and continue the reaction. When the polymerization conversion rate reaches 60%, add 2 parts of acrylonitrile and 1 part of methacrylic acid. When the conversion rate reaches 98.6%, discharge the material to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, conduct physical property tests. The results are shown in Table 1.

[0072] Comparative Example 3

[0073] 130 parts of demineralized water, 3.2 parts of sodium dodecyl sulfate, 0.2 parts of C12-glycosyl gemini cationic surfactant (n=3), 2.5 parts of dispersant NF, 0.05 parts of sodium carbonate, 0.008 parts of ferrous sulfate, 0.008 parts of EDTA-sodium iron salt, 0.02 parts of bleaching agent, 0.5 parts of tert-dodecyl mercaptan, 29 parts of acrylonitrile, and 5.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. Add 66 parts butadiene, and when the temperature of the polymerization reactor drops below 8°C, add 0.1 parts cumene hydroperoxide to start the polymerization reaction. During the process, control the polymerization reaction temperature between 5 and 8°C. Measure the dry matter every 2 hours. When the polymerization conversion rate reaches 57%, add 3 parts acrylonitrile and 2 parts methacrylic acid. When the conversion rate reaches 98.3%, discharge the material to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, conduct physical property tests. The results are shown in Table 1.

[0074] Comparative Example 4

[0075] 130 parts of demineralized water, 3.6 parts of sodium dodecyl sulfate, 0.3 parts of C14-glycosyl gemini cationic surfactant (n=2), 2.0 parts of dispersant NF, 0.05 parts of sodium carbonate, 0.01 parts of ferrous sulfate, 0.01 parts of EDTA-sodium iron salt, 0.06 parts of bleaching agent, 0.6 parts of tert-dodecyl mercaptan, 31 parts of acrylonitrile, and 6.5 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and nitrogen was used for further purging. Three times, 68 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 8°C, 0.08 parts of cumene hydroperoxide were added to start the polymerization reaction. During the process, the polymerization reaction temperature was controlled at 5-8°C. The dry matter was measured every 2 hours. When the polymerization conversion rate reached 30%, 3 parts of demineralized water were added. When the conversion rate reached 93.7%, the material was discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests were conducted. The results are shown in Table 1.

[0076] Comparative Example 5

[0077] 110 parts of demineralized water, 2.5 parts of sodium dodecyl sulfate, 0.15 parts of C13-glycosyl gemini cationic surfactant (n=1), 2.8 parts of dispersant NF, 0.06 parts of sodium pyrophosphate, 0.01 parts of ferrous sulfate, 0.01 parts of EDTA-sodium iron salt, 0.05 parts of bleach, 0.8 parts of tert-dodecyl mercaptan, 33 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to a 15L stirred and pressure-resistant polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. Then, 64 parts of butadiene were added. The polymerization reactor was then ready for use. When the temperature drops below 8℃, 0.05 parts of diisopropylbenzene hydrogen peroxide are added to start the polymerization reaction. During the process, the polymerization reaction temperature is controlled at around 15℃. The dry matter is measured every 2 hours. When the polymerization conversion rate reaches 34%, 5 parts of deionized water are added to continue the reaction. When the polymerization conversion rate reaches 59%, 2 parts of acrylonitrile and 2 parts of methacrylic acid are added. When the conversion rate reaches 98.5%, the material is discharged to prepare carboxylated nitrile butadiene latex for medical gloves. After adjusting the pH by adding alkali solution to the carboxylated nitrile butadiene latex for medical gloves, physical property tests are performed. The results are shown in Table 1.

[0078] Table 1 Test Results

[0079]

[0080]

[0081] As shown in the table above, the carboxylated nitrile butadiene latex for medical gloves provided by this invention not only has low gel content, excellent film-forming properties, mechanical stability, and strength, but also has a simple and controllable preparation method, making it easy for industrial production. Specifically, the difference between Comparative Example 1 and Example 1 is only that: in Comparative Example 1, only a single anionic emulsifier, sodium dodecyl sulfate, was added as the emulsifier, while other formulations and processes remained unchanged. Experimental results show that the carboxylated nitrile butadiene latex prepared in Comparative Example 1 has increased latex viscosity, smaller particle size, uneven heat dissipation during polymerization, and a large amount of precipitates during sampling analysis. The total solid content only reaches about 42%, the latex has poor mechanical stability, a significantly increased agglomeration content, and a significant decrease in latex performance. The difference between Comparative Example 2 and Example 2 is only that: in Comparative Example 2, only a single ferrous sulfate was added as the activator, while other formulations and processes remained unchanged. Experimental results show that in Comparative Example 2, the initial polymerization reaction is too rapid, with the dry matter reaching over 40% after 2 hours of polymerization. Due to the intense reaction and difficulty in heat dissipation, the prepared latex has poor stability and a significantly increased gel content. The only difference between Comparative Example 3 and Example 3 is that no demineralized water was added during the polymerization process in Comparative Example 3, while other formulations and processes remained unchanged. Experimental results show that without the addition of soft water, the viscosity of the system increases, which is detrimental to heat dissipation in the polymerization system, resulting in poor latex stability and a higher gel content. The only difference between Comparative Example 4 and Example 4 is that no monomers acrylonitrile and methacrylic acid were added during the polymerization process in Comparative Example 4, while other formulations and processes remained unchanged. Experimental results show that without the addition of monomers, the later polymerization reaction rate is slower, resulting in a lower final total solids content, smaller particle size, and poorer mechanical stability. The only difference between Comparative Example 5 and Example 5 is that the polymerization temperature was controlled at around 15°C in Comparative Example 5, while other formulations and processes remained unchanged. Experimental results show that increasing the polymerization temperature accelerates the polymerization reaction rate, worsens system stability, and results in a higher raw rubber gel content.

[0082] The carboxylated nitrile latexes obtained in the above embodiments and comparative examples were used to make nitrile latex gloves under the same application conditions according to the vulcanization base formulations in Table 2 below, and mechanical properties were tested (GB / T528-2009). The specific results are shown in Table 3 below.

[0083] Table 2 Basic Vulcanization Formulation

[0084]

[0085]

[0086] Table 3 Performance of Nitrile Latex Gloves

[0087] Tensile strength / MPa Elongation at break / % Example 1 30.2 604 Example 2 31.1 586 Example 3 29.6 597 Example 4 31.5 611 Example 5 30.4 588 Comparative Example 1 20.3 435 Comparative Example 2 20.5 487 Comparative Example 3 23.3 542 Comparative Example 4 23.8 534 Comparative Example 5 25.4 529

[0088] As can be seen from the data in the table above, the nitrile gloves made from carboxylated nitrile latex provided by the present invention have excellent mechanical properties.

[0089] Of course, the present invention may have other various embodiments. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and modifications according to the present invention, but these corresponding changes and modifications should all fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing carboxylated butadiene-acrylonitrile latex for medical gloves, characterized in that, Includes the following steps: (1) Mix deionized water, emulsifier, dispersant, molecular weight regulator, activator, reducing agent, electrolyte, methacrylic acid and acrylonitrile, add oxygen scavenger and butadiene to obtain a mixture; (2) After controlling the temperature of the mixture to 5-8°C, an initiator is added and a polymerization reaction is carried out at 5-8°C. When the polymerization conversion rate reaches 30%-60%, deionized water, acrylonitrile and methacrylic acid are added. When the polymerization conversion rate is greater than 98%, the material is discharged to obtain the carboxylated butadiene nitrile latex for medical gloves. The emulsifier is a mixture of anionic and cationic emulsifiers, wherein the anionic emulsifier is sodium dodecyl sulfate and the cationic emulsifier is a glycosyl gemini cationic surfactant. The activator is a mixture of ferrous sulfate and EDTA salt.

2. The preparation method according to claim 1, characterized in that, When the polymerization conversion rate reaches 30% to 35%, demineralized water is added; when the polymerization conversion rate reaches 55% to 60%, acrylonitrile and methacrylic acid monomers are added.

3. The preparation method according to claim 1, characterized in that, By weight, the carboxylated nitrile latex for medical gloves comprises the following raw materials: 64-70 parts butadiene, 28-38 parts acrylonitrile, 3.5-8.0 parts methacrylic acid, 2.5-4.0 parts emulsifier, 1.0-3.0 parts dispersant, 0.02-0.08 parts electrolyte, 0.005-0.05 parts activator, 0.02-0.06 parts reducing agent, 0.4-1.0 parts molecular weight regulator, 0.005-0.02 parts oxygen scavenger, 0.04-0.10 parts initiator, and 113-135 parts desalinated water.

4. The preparation method according to claim 3, characterized in that, In step (2), 3-5 parts of deionized water, 2-5 parts of acrylonitrile, and 0.5-2 parts of methacrylic acid are added by mass.

5. The preparation method according to claim 1, characterized in that, The structural formula of the glycosyl gemini cationic surfactant is as follows: Where n = 1 to 3, and R is an alkyl group.

6. The preparation method according to claim 3, characterized in that, R is selected from C12 to C14 straight-chain alkyl groups.

7. The preparation method according to claim 1, characterized in that, The mass ratio of the anionic emulsifier to the cationic emulsifier in the emulsifier is 1:0.05 to 0.

1.

8. The preparation method according to claim 1, characterized in that, The mass ratio of ferrous sulfate to EDTA salt in the activator is 1:0.9 to 1.

1.

9. The preparation method according to claim 1, characterized in that, The EDTA salt is EDTA-sodium iron salt.

10. The preparation method according to claim 1, characterized in that, The initiator is a low-temperature redox initiator; The electrolyte is any one of sodium carbonate, sodium bicarbonate, and sodium pyrophosphate.

11. The preparation method according to claim 10, characterized in that, The initiator is cumene hydroperoxide and / or dicumene hydroperoxide.

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