A carboxylated butadiene nitrile latex, its preparation method and application

Abstract

This invention provides a carboxylated nitrile butadiene latex, its preparation method, and its application. The carboxylated nitrile butadiene latex, by mass parts, is composed of the following raw materials: butadiene, acrylonitrile, methacrylic acid, emulsifier, dispersant, electrolyte, ferrous sulfate, reducing agent, molecular weight regulator, oxygen scavenger, initiator, and demineralized water. The emulsifier is a mixture of anionic and cationic emulsifiers; the anionic emulsifier is sodium dodecyl sulfate, and the cationic emulsifier is a glycosyl gemini cationic surfactant. The mass ratio of the anionic emulsifier to the cationic emulsifier is 1:0.05–0.1. This carboxylated nitrile butadiene latex not only has low gel content and high mechanical stability, but its preparation method is also simple and controllable, making it easy for industrial production.

Description

Technical Field

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

[0002] Carboxylated nitrile butadiene latex is a high-molecular-weight white emulsion produced by emulsion polymerization of butadiene, acrylonitrile, and unsaturated carboxylic acids. Due to the presence of polar nitrile and carboxyl groups in its molecular chain, its properties are superior to ordinary nitrile butadiene latex, exhibiting improved mechanical stability, thawing stability, adhesion, film-forming properties, and post-processing performance. The resulting latex possesses excellent oil, chemical, and abrasion resistance, good flowability, high tensile strength, and unique adhesive properties, exhibiting good compatibility with polar polymers such as starch, casein, vinyl resins, phenolic resins, and chlorine-formaldehyde resins. However, most existing carboxylated nitrile butadiene latex production processes employ medium-to-high temperature methods, and the resulting latex products generally suffer from high gel content, poor film-forming properties, or complex operation, hindering industrial-scale production.

[0003] For example, Chinese patent document CN201510152547.8 discloses a carboxylated nitrile latex for impregnating nonwoven fabrics and its preparation method. The polymerization reactor is evacuated and purged with nitrogen. Then, demineralized water, emulsifier, molecular weight regulator, pH buffer, α,β-ene-bonded unsaturated nitrile monomer, conjugated diene monomer, C3-C5 vinyl unsaturated carboxylic acid monomer, cyclopentadienylsilane, perfluorinated α,β-ene-bonded olefin, and initiator are added continuously. The emulsifier is anionic. The method involves one or more of the following: a nonionic emulsifier, a polyoxyethylene ether nonionic emulsifier, and a quaternary ammonium salt amphoteric emulsifier. The emulsifier is preferably a nonionic emulsifier and / or a quaternary ammonium salt amphoteric emulsifier, more preferably a nonionic emulsifier and a quaternary ammonium salt amphoteric emulsifier in a mass ratio of 1:1.2–2. The polymerization reaction is carried out at 65°C for 8 hours. After the reaction, the temperature is lowered to 35°C, and after 2 hours of curing, the material is discharged at a lower temperature. A pH adjuster is added to adjust the pH to 8–11, thus obtaining carboxylated nitrile butadiene latex. The drawbacks of this technical solution are: the method uses a high-temperature polymerization method and a continuous feeding process, which is complex to operate and difficult to implement industrially.

[0004] 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 is further raised to 36–40°C, and the reaction continues 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. The reaction is stopped when the conversion rate reaches 98%, resulting in a carboxylated nitrile butadiene latex with a solid content of 43%–45%. The drawbacks of this technique are: the use of a medium-to-high temperature polymerization method with segmented temperature control makes operation complex and difficult to control, which is not conducive to industrial production. Furthermore, the high degree of branching and cross-linking in the product leads to a high gel content.

[0005] Chinese patent document CN202111163259.4 discloses a nitrile rubber latex, its preparation method, and its application. By weight, the raw materials for preparing the nitrile rubber latex include 78-95 parts butadiene, 38-55 parts acrylonitrile, 5-10 parts acrylate, 1-3 parts N-(hydroxymethyl)acrylamide, 1-5 parts emulsifier, 1-3 parts initiator, 0.1-2 parts molecular weight regulator, 0.1-2 parts pH regulator, and 0.5-2 parts film-forming aid. This document uses acrylate and N-(hydroxymethyl)acrylamide to modify the nitrile rubber latex. Because acrylate has broad adhesive properties, excellent flexural strength, and resistance to crack growth, the resulting nitrile rubber latex exhibits better adhesion and strength. Simultaneously, the addition of N-(hydroxymethyl)acrylamide, with its self-crosslinking properties, allows the nitrile rubber latex to form a film quickly, preventing yellowing of the film due to excessively long film-forming time. The resulting nitrile latex exhibits excellent adhesion and rapid film formation, thus meeting the production and usage requirements for oil-resistant lining gloves. Furthermore, its high strength ensures long-term durability. However, this technical solution has some drawbacks: the medium-to-high temperature polymerization method results in a high degree of branching and cross-linking in the product, leading to a high gel content.

[0006] 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 defects or shortcomings of this technical solution are as follows: the method adopts a medium-high temperature polymerization method, a continuous dripping process, and uses seed latex for graft polymerization, making the feeding process complex and difficult to realize industrial production.

[0007] Chinese patent document CN201710799349.X discloses a production process for carboxylated nitrile butadiene latex, comprising the following steps: (1) Weighing raw materials, including 75-100 parts of deionized water, 1-2 parts of molecular weight regulator, 0.1-0.5 parts of pH buffer, and 3-5 parts of emulsifier, adding the above raw materials to a polymerization reactor, stirring at a rate of 550-750 r / min for 1-2 hours at a temperature of 28-45°C, mixing evenly, and then purging with nitrogen and drawing a vacuum; (2) Weighing raw materials, including 38-50 parts of butadiene, 20-30 parts of acrylonitrile, 8-15 parts of acrylic acid monomer, and 2-5 parts of unsaturated carboxylic acid, adding the above raw materials to the polymerization reactor in step 1. In the reactor, keep the temperature and speed of step 1 constant, and stir for 1 to 3 hours to obtain an emulsion; (3) slowly heat the emulsion obtained in step 2 at a rate of 3 to 5 °C / min, while adding initiator and deionized water, and control the addition flow ratio of initiator and deionized water to 1:6.6 to 8. After the reaction temperature rises to 58 to 75 °C and the initiator and deionized water have been added, keep the reaction at the temperature until the conversion rate reaches more than 99% to obtain a latex; (4) transfer the latex obtained in step 3 into a degassing reactor for degassing treatment, and then add 1.5 to 4% of the total amount of latex as an auxiliary agent. After being dispersed evenly by a high-speed disperser, the mixture is cooled and packaged to obtain the required carboxylated nitrile butadiene latex. The defects or shortcomings of this technical solution are: the method adopts a medium-high temperature polymerization method, the feeding process is complicated, and the industrial implementation is difficult.

[0008] Chinese patent document CN201610140264.6 discloses a carboxylated nitrile butadiene latex and its preparation method, comprising the following steps: (1) in the presence of an initiator, at a reaction temperature of 10-25°C, acrylonitrile, vinyl unsaturated carboxylic acid monomer and emulsifier are contacted in water, the contact conditions causing a copolymerization reaction to generate a copolymer with a particle diameter of 50-90 nm, to obtain a seed latex; (2) at a reaction temperature of 25-35°C, a mixture of acrylonitrile, butadiene and a molecular weight regulator is continuously added to the seed latex obtained in step (1), and after the addition is completed, an emulsifier is added and the reaction continues, wherein the emulsifier is sodium dodecyl diphenyl ether sulfonate and / or octylphenol polyoxyethylene ether; (3) at a reaction temperature of 35-45°C, an initiator is added to the reaction mixture obtained in step (2) and the reaction continues to be carried out to prepare a carboxylated nitrile butadiene latex. The shortcomings or deficiencies of this technical solution are as follows: This method uses high-temperature polymerization and a continuous feeding process, which is complex to operate and difficult to implement in industrial applications. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a carboxylated nitrile butadiene latex, its preparation method and application, so as to solve the problems that the existing carboxylated nitrile butadiene latex and its preparation method generally have high gel content or are difficult to implement in industrial applications.

[0010] Therefore, the present invention provides the following technical solution:

[0011] A carboxylated nitrile butadiene latex, by mass fraction, is composed of the following raw materials: 64-70 parts butadiene, 26-33 parts acrylonitrile, 3.0-6.0 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 ferrous sulfate, 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 125-140 parts desalinated water;

[0012] 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.

[0013] The mass ratio of the anionic emulsifier to the cationic emulsifier in the emulsifier is 1:0.05 to 0.1.

[0014] Optionally, the structural formula of the glycosyl gemini cationic surfactant is as follows:

[0015]

[0016] Where n = 1 to 3, and R is an alkyl group.

[0017] Optionally, R is selected from C12 to C14 straight-chain alkyl groups.

[0018] Optionally, R is selected from C12 straight-chain alkyl groups.

[0019] Nitrile butadiene latex typically has a solid content of 25%–30%, while carboxylated nitrile butadiene latex used in work gloves usually requires a solid content of over 40%. 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 will inevitably affect the viscosity and pH of the system, while an increased conversion rate will lead to a significant increase in gel content in the later stages of the reaction. Especially when the solid content reaches a certain level, the viscosity of the system increases, the latex easily becomes a paste, and loses its fluidity. In the preparation of high-solids carboxylated nitrile butadiene latex, the main method to reduce the viscosity of the system is to synthesize carboxylated nitrile butadiene latex with a large particle size distribution.

[0020] 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 a larger latex particle size distribution. This allows smaller particles to fill the gaps between larger particles, increasing the latex particle packing volume and producing high-solids-content carboxylated nitrile butadiene latex.

[0021] Optionally, the initiator is a low-temperature redox initiator, preferably cumene hydroperoxide and / or dicumene hydroperoxide.

[0022] Optionally, the electrolyte is any one of sodium carbonate, sodium bicarbonate, and sodium pyrophosphate.

[0023] 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.

[0024] The present invention also provides a method for preparing the above-mentioned carboxylated butadiene nitrile latex, comprising the following steps:

[0025] Deionized water, emulsifier, dispersant, molecular weight regulator, activator, reducing agent, electrolyte, methacrylic acid and acrylonitrile are mixed, then an oxygen scavenger and butadiene are added. After controlling the system temperature to 8-15°C, an initiator is added and polymerization is carried out at 8-15°C. When the polymerization conversion rate reaches 95%, 0.05-0.2 parts of a terminator are added to obtain the carboxylated nitrile latex.

[0026] Optionally, the method further includes the step of adjusting the pH of the carboxylated nitrile latex to 8.0-10.0 with a 3wt% to 5wt% KOH solution after adding the terminator.

[0027] Optionally, the terminator may be at least one of the following commonly used agents in the industry: sodium nitrite, actinol reagent, and p-aminoazobenzene.

[0028] Regarding the formulation of the carboxylated nitrile latex in this invention, the inventors discovered through research that controlling the polymerization reaction temperature to 8–15°C is beneficial for controlling the latex stability and gel content.

[0029] The present invention also provides a work gloves made from the above-mentioned carboxylated nitrile latex or the carboxylated nitrile latex prepared by the above-mentioned method.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] The carboxylated nitrile butadiene latex provided by this invention breaks the traditional limitation that anionic and cationic surfactants cannot be used together by introducing a specific glycosyl gemini cationic surfactant and anionic surfactant compounded together during the polymerization process. This compounded emulsifier further reduces the critical micelle concentration and surface tension of the solution, improving emulsification efficiency. Combined with ferrous sulfate activator and other raw materials, the synergistic effect significantly improves the stability and production efficiency of the latex. Polymerization at 8–15°C produces a carboxylated nitrile butadiene latex with a solid content of 42.0%–44.0%, viscosity ≤60 mPa·s, particle size 70–90 nm, mechanical stability ≤0.1%, and gel content <15.0%. This latex not only exhibits low gel content, excellent film-forming properties, mechanical stability, and strength, but also boasts a simple and controllable preparation method, facilitating industrial production. Detailed Implementation

[0032] 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.

[0033] 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.

[0034] Evaluation and analysis methods:

[0035] Total solids content: Complies with standard SH / T 1154-2011

[0036] Latex viscosity: Complies with standard SH / T 1152-2014

[0037] pH value: Complies with standard SH / T 1150-2011

[0038] Mechanical stability: Complies with standard SH / T 1151-2011

[0039] Surface tension: Complies with standard SH / T 1156-2014

[0040] Raw gum gel content: Complies with standard SH / T 1050-91

[0041] 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:

[0042] Butadiene, conforming to GB / T 13291-2008 standard, industrial grade, purity ≥99.5%, Lanzhou Petrochemical Company;

[0043] Acrylonitrile, conforming to GB / T 7717.1-2008 standard, industrial grade, purity ≥99.5%, Lanzhou Petrochemical Company;

[0044] Methacrylic acid, industrial grade, purity >99%, Sinopharm Chemical Reagent Co., Ltd.

[0045] 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.

[0046] Sodium dodecyl sulfate, industrial grade, purity >96%, Lanzhou Petrochemical Company;

[0047] Ferrous sulfate, industrial grade, purity ≥98%, Lanzhou Petrochemical Company;

[0048] Diao Bai Kuai: Industrial product, purity ≥98%, Lanzhou Petrochemical Company;

[0049] Ethylenediaminetetraacetic acid (EDTA-sodium iron), industrial grade, purity (EDTA on dry basis) ≥97.0%, Lanzhou Petrochemical Company;

[0050] Tert-dodecyl mercaptan, imported industrial product, purity ≥97.3%, Lanzhou Petrochemical Company;

[0051] Diisopropylbenzene hydrogen peroxide, industrial grade, purity ≥80%, Lanzhou Petrochemical Company;

[0052] Oxygen scavenger, industrial grade, Na2S2O4 content ≥85.0%, Lanzhou Petrochemical Company.

[0053] Example 1

[0054] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 136 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, 0.04 parts of bleach, 0.5 parts of tert-dodecyl mercaptan, 27 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.005 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 15°C, 0.06 parts of dicumyl peroxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 95.4%, 0.05 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 3 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0055] Example 2

[0056] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 126 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, 0.03 parts of bleach, 0.55 parts of tert-dodecyl mercaptan, 32 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.009 parts of oxygen scavenger were added, and nitrogen was used to purge the reactor three times. 65 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.06 parts of dicumyl peroxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 95.2%, 0.2 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 4 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0057] Example 3

[0058] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 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, 0.02 parts of bleach, 0.5 parts of tert-dodecyl mercaptan, 29 parts of acrylonitrile, and 5.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and nitrogen was used to purge the reactor three times. 66 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.1 parts of cumene hydroperoxide were added to start the polymerization reaction. The polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 95.1%, 0.1 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 5 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0059] Example 4

[0060] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 140 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, 0.06 parts of bleach, 0.6 parts of tert-dodecyl mercaptan, 26 parts of acrylonitrile, and 6.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.03 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 68 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.08 parts of cumene hydroperoxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 94.7%, 0.1 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 5 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0061] Example 5

[0062] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 132 parts of demineralized water, 2.5 parts of sodium dodecyl sulfate, 0.15 parts of C13-glycosyl gemini cationic surfactant (n=3), 2.8 parts of dispersant NF, 0.06 parts of sodium pyrophosphate, 0.04 parts of ferrous sulfate, 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 the polymerization reactor. After evacuation, 0.05 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 64 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.05 parts of dicumyl peroxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 95.1%, 0.08 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 5 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0063] Comparative Example 1

[0064] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 136 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, 0.04 parts of bleach, 0.5 parts of tert-dodecyl mercaptan, 27 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.005 parts of oxygen scavenger were added, and nitrogen was used to purge the reactor three times. 70 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.06 parts of dicumyl peroxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 92.4%, 0.05 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 3 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0065] Comparative Example 2

[0066] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 126 parts of demineralized water, 3 parts of sodium dodecyl sulfate, 0.6 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, 0.03 parts of bleach, 0.55 parts of tert-dodecyl mercaptan, 32 parts of acrylonitrile, and 3.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.009 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 65 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.06 parts of dicumyl peroxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 78.2%, 0.2 parts of terminator were added to prepare carboxylated nitrile latex. The pH was adjusted by adding 4 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0067] Comparative Example 3

[0068] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 100 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, 0.02 parts of bleach, 0.5 parts of tert-dodecyl mercaptan, 29 parts of acrylonitrile, and 5.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.01 parts of oxygen scavenger were added, and nitrogen was used to purge the reactor three times. 66 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 15°C, 0.1 parts of cumene hydroperoxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled between 8 and 15°C. The dry matter content was measured every 2 hours. When the conversion rate reached 85.1%, 0.1 parts of terminator were added to prepare carboxylated nitrile butadiene latex. 5 wt% KOH solution was added to adjust the pH, and then the physical properties were tested. The results are shown in Table 1.

[0069] Comparative Example 4

[0070] The polymerization reaction was carried out in a 15L stirred pressure vessel. The amount of each monomer and additive added was based on the weight of 100 parts of monomer. At the start of the polymerization reaction, 140 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, 0.06 parts of bleach, 0.6 parts of tert-dodecyl mercaptan, 26 parts of acrylonitrile, and 6.0 parts of methacrylic acid were added to the polymerization reactor. After evacuation, 0.03 parts of oxygen scavenger were added, and the reactor was purged with nitrogen three times. 68 parts of butadiene were added. When the temperature of the polymerization reactor dropped below 25°C, 0.08 parts of cumene hydroperoxide were added to start the polymerization reaction. During the process, the polymerization temperature was controlled at 20-25°C. The dry matter content was measured every 2 hours. When the conversion rate reached 94.7%, 0.1 parts of terminator were added to prepare carboxylated nitrile butadiene latex. The pH was adjusted by adding 5 wt% KOH solution, and then the physical properties were tested. The results are shown in Table 1.

[0071] Table 1 Test Results

[0072]

[0073] As can be seen from the data in the table above, the carboxylated nitrile butadiene latex provided by the present 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. The experimental results show that the surface tension and viscosity of the carboxylated nitrile butadiene latex emulsion system prepared in Comparative Example 1 increased, the heat dissipation of the polymerization reaction was uneven, and there were more precipitates during sampling analysis. The total solid content could only reach about 40%, the mechanical stability of the latex was poor, the coagulation content increased significantly, and the latex performance decreased significantly.

[0074] The only difference between Comparative Example 2 and Example 2 is that the amount of C12-glycosyl gemini cationic surfactant was increased in Comparative Example 2, so that the ratio of sodium dodecyl sulfate to C12-glycosyl gemini cationic surfactant reached 1:0.2. Other formulations and processes remained unchanged. The experimental results showed that the increased amount of cationic surfactant in Comparative Example 2 led to a decrease in the stability of the polymerization system, which had a great impact on the polymerization reaction. A large number of gel particles were precipitated during the reaction, and the latex solid content could only reach about 35%.

[0075] The only difference between Comparative Example 3 and Example 3 is that the amount of demineralized water in Comparative Example 3 was reduced by 100 parts, while other formulations and processes remained unchanged. The experimental results showed that after the amount of demineralized water was reduced to a certain extent, the viscosity of the system increased sharply, it was difficult to dissipate heat through stirring, the stability of the system decreased, the conversion rate of the polymerization reaction could only reach about 85%, and the latex flowability was poor.

[0076] The only difference between Comparative Example 4 and Example 4 is that the polymerization temperature was increased in Comparative Example 4, and the polymerization temperature was controlled at around 20-25°C. Other formulations and processes remained unchanged. The experimental results showed that the polymerization reaction rate was accelerated when the polymerization temperature was increased, the system stability was worsened, and the gel content increased significantly.

[0077] 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 carboxylated nitrile latex characterized in that, The carboxylated nitrile latex, by mass fraction, is composed of the following raw materials: 64-70 parts butadiene, 26-33 parts acrylonitrile, 3.0-6.0 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 ferrous sulfate, 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 125-140 parts desalinated water; 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 mass ratio of the anionic emulsifier to the cationic emulsifier in the emulsifier is 1:0.05 to 0.1; The structural formula of the glycosyl gemini cationic surfactant is as follows: Wherein, n=1~3, and R is selected from C12~C14 straight-chain alkyl groups; The preparation method of the carboxylated butadiene nitrile latex includes the following steps: In an inert atmosphere, deionized water, emulsifier, dispersant, molecular weight regulator, ferrous sulfate, reducing agent, electrolyte, methacrylic acid and acrylonitrile are mixed, then an oxygen scavenger and butadiene are added. After controlling the system temperature to 8-15°C, an initiator is added and polymerization is carried out at 8-15°C. When the polymerization conversion rate reaches 95% or more, 0.05-0.2 parts of a terminator are added to obtain the carboxylated nitrile latex.

2. The carboxylated nitrile latex of claim 1, wherein, R is selected from C12 straight-chain alkyl groups.

3. The carboxylated nitrile latex of claim 1, wherein, The initiator is a low-temperature redox initiator.

4. The carboxylated nitrile latex of claim 3, wherein, The initiator is cumene hydroperoxide and / or dicumene hydroperoxide.

5. The carboxylated nitrile latex of claim 1, wherein, The electrolyte is at least one of sodium carbonate, sodium bicarbonate, and sodium pyrophosphate.

6. A safety glove characterized by It is prepared from the carboxylated butadiene-acrylonitrile latex according to any one of claims 1-5.

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