Preparation method for copolymerization of chloroprene and 2, 3-dichlorobutadiene-1, 3

Abstract

The invention discloses a preparation method for copolymerization of chloroprene and 2, 3-dichlorobutadiene-1, 3, which comprises the following steps: (1) pre-emulsification: adding an emulsifier raw material into an emulsification kettle, stirring, sequentially adding part of polymer raw materials into the emulsification kettle after the emulsifier raw material is completely dissolved, and stirring for a set time to obtain a pre-emulsion; (2) prepolymerization: introducing nitrogen into a polymerization kettle to replace oxygen, adding a 2, 3-dichlorobutadiene-1, 3 monomer into the polymerization kettle, adding an initiator raw material, and stirring to obtain a prepolymerized emulsion; (3) polymerization: dropwise adding the pre-emulsion obtained in the step (1), an initiator raw material and a molecular weight regulator into the pre-polymerized emulsion obtained in the step (2) at the same time, and keeping the temperature for 4-6 hours to obtain a polymerized emulsion; (4) terminating the reaction; and (5) post-treatment. The method is simple in process, high in stability, high in product quality and yield, capable of effectively improving the production efficiency and very suitable for industrial application.

Description

Technical Field

[0001] This invention relates to a method for preparing a copolymer of chloroprene and 2,3-dichloroprene-1,3. Background Technology

[0002] The information disclosed in this background section is intended only to enhance some understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that the information constitutes prior art known to those skilled in the art.

[0003] Chloroprene rubber (CR) is a synthetic rubber widely used in various industrial and consumer products. Its main raw material, chloroprene, is produced through a polymerization reaction. This material possesses excellent physical and mechanical properties, such as heat resistance, oil resistance, acid and alkali resistance, and sunlight resistance, making it widely used in the production of rubber conveyor belts, transmission belts, wires and cables, hoses, rubber sheets, and sealing products. However, as a crystalline rubber, chloroprene rubber's inherent crystallinity can cause it to harden and become brittle at lower temperatures. This is because the crystalline structure restricts the free rotation and stretching of polymer chains, leading to a decrease in its flexibility. Furthermore, chloroprene rubber has relatively poor storage stability and is prone to delamination and gelation, all of which affect its application performance to some extent. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention has conducted modification research on chloroprene rubber. The method of introducing 2,3-dichlorobutadiene-1,3 (hereinafter referred to as 2,3DCB) units into the chloroprene molecular chain has shown good application prospects. Through copolymerization, this method can effectively break the regularity of the chloroprene molecular chain, thereby improving the low-temperature flexibility and storage stability of chloroprene rubber. These modified chloroprene rubbers have excellent anti-crystallization properties, perform well in low-temperature environments, and have a soft texture, making them suitable for various industrial fields.

[0005] The technical solution adopted in this invention is as follows: In a first aspect of the present invention, a method for preparing a copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 is provided, the method comprising the following steps: (1) Pre-emulsification: Add the emulsifier raw material to the emulsification kettle and stir for 20-30 minutes. After it is completely dissolved, add a portion of the polymer raw material to the emulsification kettle in sequence and stir rapidly for a set time to obtain the pre-emulsion. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 2,3-Dichlorobutadiene-1,3 monomer is added to the polymerization reactor. The temperature is controlled at 50-65℃. Initiator raw materials are added and stirred for 10-20 minutes to obtain a prepolymer emulsion. (3) Polymerization: The pre-emulsion obtained in step (1), the initiator raw material and the molecular weight regulator are simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure is controlled at 0.2-0.5 MPa, and the polymerized emulsion is obtained after keeping it at the temperature for 4-6 hours. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature; add a buffer to adjust the pH of the emulsion to neutral, and add a terminator to stop the reaction; (5) Post-treatment: The demulsifier was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water to remove the demulsifier, as well as the residual emulsifier and initiator. The washed polymer was dehydrated and dried by centrifugation. The final moisture content was measured to be ≤5w / w.

[0006] In one or more embodiments of the present invention, in step (1), the emulsifier raw material is composed of the following parts by weight: 8-12 parts of anionic emulsifier, 16-20 parts of nonionic emulsifier, and 460-650 parts of deionized water.

[0007] Preferably, the anionic emulsifier is selected from at least one of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium stearate, calcium stearate, and sodium oleate.

[0008] More preferably, the anionic emulsifier is a combination of sodium dodecyl sulfate and sodium oleate.

[0009] Most preferably, the mass ratio of sodium dodecyl sulfate to sodium oleate is (1-1.5):(1.5-2).

[0010] Preferably, the nonionic emulsifier is selected from at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and fatty acid polyoxyethylene ester.

[0011] More preferably, the nonionic emulsifier is fatty alcohol polyoxyethylene ether.

[0012] Most preferably, the fatty alcohol polyoxyethylene ether is isotretinoin polyoxyethylene ether. When the isotretinoin polyoxyethylene ether is a combination of isotretinoin polyoxyethylene ether T08 and isotretinoin polyoxyethylene ether T12, and the mass ratio of isotretinoin polyoxyethylene ether T08 to isotretinoin polyoxyethylene ether T12 is (2-3):(1-2), the emulsification effect is best when combined with sodium dodecyl sulfate and sodium oleate in the system.

[0013] In one or more embodiments of the present invention, in step (1), the polymer raw material is composed of the following parts by weight: 200-400 parts of chloroprene and 100-225 parts of butadiene. In the present invention, by using specific polymer raw materials and adding them sequentially into an emulsification tank containing emulsifier raw materials, the polymer raw materials are fully pre-emulsified in the emulsification tank, so that the provided copolymer has excellent physical and mechanical properties and temperature resistance.

[0014] In one or more embodiments of the present invention, in step (1), the stirring conditions are: a stirring speed of 1500-2000 rpm and a stirring time of 20-30 min. By stirring and dispersing the emulsifier raw material in an emulsification tank, the polymer raw material and the emulsifier raw material are fully contacted and mixed evenly, and pre-emulsification is performed. During the research process, the applicant found that when specific polymer raw materials and emulsifier raw materials are used, and the stirring speed is controlled at 1500-2000 rpm and the stirring time is 20-30 min, a fully dispersed and highly stable pre-emulsion can be obtained.

[0015] In one or more embodiments of the present invention, during nitrogen purging in step (2), the gauge pressure is 0.05~0.2MPa, and a "pressurization-depressurization" cycle method is adopted (repeated 3 times). Each time the pressure is increased to 0.1 MPa and then depressurized to atmospheric pressure, which can effectively reduce the oxygen content to a safe limit. The reaction temperature is controlled at 50-65℃, and the stirring speed is controlled at 500-800rpm.

[0016] In one or more embodiments of the present invention, in step (2), the 2,3-dichlorobutadiene-1,3 monomer is 200-400 parts by weight.

[0017] In one or more embodiments of the present invention, in step (2), the initiator raw material is composed of the following parts by weight: 1-3 parts potassium persulfate and 4-6 parts water. By controlling the reaction temperature to 50-65°C, the chloroprene composition is prepolymerized using potassium persulfate for 10-20 minutes to obtain a prepolymerized emulsion with uniform particle size and high stability.

[0018] In one or more embodiments of the present invention, in step (3), the dropping conditions are as follows: dropping time is 3-4 hours, dropping temperature is 50-65°C; the initiator raw material is composed of the following parts by weight: potassium persulfate 1-4 parts, water 4-6 parts; the molecular weight regulator is n-dodecyl mercaptan 0.1-0.5 parts. In the present invention, by controlling the dropping temperature and time, the pre-emulsion and the initiator raw material are simultaneously added to the prepolymer emulsion, so that the polymer raw material in the system can be fully polymerized. After keeping it at the temperature for 4-6 hours, a polymer emulsion with a conversion rate of 95% can be obtained.

[0019] The polymerization temperature of this invention is controlled between 50-65℃. If the temperature is too low, the initiator decomposition rate decreases, free radical generation decreases, and the reaction rate drops significantly, resulting in a low conversion rate and a high amount of residual monomer; thus, the reaction time needs to be extended, increasing energy consumption. If the temperature is too high, it will lead to branching of the polymer and excessively rapid free radical generation, resulting in concentrated exothermic reactions and a tendency to trigger rapid polymerization. This, in turn, reduces the processability of the copolymer.

[0020] In one or more embodiments of the present invention, in step (4), the buffer is 1-3 parts by weight of sodium bicarbonate; the terminator is composed of the following raw materials by weight: 1-3 parts of tert-butylcatechol and 1-3 parts of water; when the reaction conversion rate reaches 90%, the buffer and terminator are simultaneously added to the polymerization reactor and stirred for 20 minutes; to ensure the quality and performance of the finally prepared copolymer.

[0021] In one or more embodiments of the present invention, in step (5), the demulsifier is a 5w / w%-10w / w% calcium chloride solution, and the amount of calcium chloride added is usually 1.0% to 3.0% of the total weight of the emulsion (calculated as anhydrous CaCl2).

[0022] In one or more embodiments of the present invention, in step (5), the stirring speed of the CaCl2 solution is controlled at 200~400 rpm and the dropping speed is 1s / d to avoid rapid demulsification leading to particle coarsening.

[0023] In one or more embodiments of the present invention, in step (5), deionized water at 50-60°C is used for washing, and the amount of water used is 2 to 3 times the mass of the wet polymer; the washing is repeated 2 to 3 times.

[0024] In one or more embodiments of the present invention, in step (5), the speed of the centrifuge is controlled at 2000~3000 rpm, and centrifugation is performed for 10-15 minutes.

[0025] In a second aspect of the invention, the use of the method described above or the product obtained by the method described above in the preparation of chloroprene rubber is provided.

[0026] Compared with the related technologies known to the inventors, one of the technical solutions of the present invention has the following beneficial effects: 1. This invention employs a combination of anionic and nonionic emulsifiers as the emulsifier. Due to the strong water solubility of the anionic emulsifier sodium dodecyl sulfate, it can rapidly adsorb onto the interface, reducing the initial interfacial energy. Simultaneously, the long carbon chain structure (C18) of sodium oleate enhances its anchoring ability in the oil phase, forming a dense interfacial film together with isomeric tridecyl ether. These two components work synergistically, and the addition of the nonionic emulsifier further reduces the charge repulsion effect between anions, thereby improving the mechanical strength of the composite interfacial film and effectively preventing droplet aggregation, thus preparing a uniformly dispersed pre-emulsion.

[0027] 2. The present invention adopts a prepolymerization method, first prepolymerizing the highly active 2,3-dichlorobutadiene-1,3 monomer, and avoiding rapid polymerization through strict temperature control, so as to obtain a prepolymerized emulsion with uniform emulsion particle size and high stability.

[0028] 3. This invention uses emulsion polymerization to achieve a solid content of 40-50%, which significantly improves the yield per batch; free radicals are rapidly initiated in the aqueous phase, and the conversion rate can reach 95%.

[0029] 4. This invention can precisely control the polymer chain length through the synergistic effect of emulsifiers and molecular weight regulators, thereby improving the physical and mechanical properties of copolymers.

[0030] 5. This invention employs an emulsion polymerization process, which facilitates continuous feeding and discharging, resulting in an efficiency improvement of over 30% compared to batch bulk polymerization. Post-processing is simple and well-established; after drying, a powdered solid product is directly obtained.

[0031] 6. The present invention has a high raw material utilization rate, can recover residual monomers, and the cost of water-based media is much lower than that of organic solvents, thus reducing production costs.

[0032] 7. The process of this invention is simple, highly stable, and produces high-quality products with high yields, effectively improving production efficiency and making it very suitable for industrial applications. The prepared chloroprene-2,3-dichloroprene-1,3 copolymer has wide applications in rubber, coatings, and adhesives. Attached Figure Description

[0033] The accompanying drawings, which form part of this specification, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0034] Figure 1 This is a picture of the polymer emulsion in Example 1. Detailed Implementation

[0035] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0036] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the exemplary embodiments of the present invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0038] In this invention, sodium dodecyl sulfate and sodium oleate were purchased from Beijing Bailingwei Technology Co., Ltd.; the brand of the isomeric tridecyl alcohol polyoxyethylene ether T08 and isomeric tridecyl alcohol polyoxyethylene ether T12 is BASF and was purchased from BASF (China) Co., Ltd.

[0039] Example 1 (1) Pre-emulsification: By weight, 20 parts of emulsifier raw material are added to the emulsification tank and stirred for 30 minutes. After complete dissolution, 200 parts of chloroprene and 200 parts of butadiene are added to the emulsification tank in sequence. After stirring at 1500-2000 rpm for 30 minutes, a pre-emulsion is obtained. The emulsifier raw material is composed of the following raw materials by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium oleate in a mass ratio of 1:1. The nonionic emulsifier includes isotretinoin polyoxyethylene ether T08 and isotretinoin polyoxyethylene ether T12 in a mass ratio of 2:1. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 400 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 50-65℃. 1 part of potassium persulfate initiator and 6 parts of water are added to the raw material. The mixture is stirred for 15 minutes to obtain a prepolymer emulsion. (3) Polymerization; The pre-emulsion obtained in step (1), 1 part potassium sulfate initiator, 4 parts water, and 0.1 part n-dodecyl mercaptan, a molecular weight regulator, are simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure is controlled at 0.2-0.5 MPa, and the mixture is kept at this temperature for 5 hours to obtain the polymerized emulsion. Figure 1Weigh a small amount of emulsion (m1, approximately 1-2 g) into a pre-weighed aluminum dish. Dry in a 105°C oven for 2 hours until constant weight, then cool and weigh m2. According to the formula solid content (%) = m1 / m2 * 100, the solid content is 46.30%. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 2 parts of water to stop the reaction; (5) Post-treatment: 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 50°C for 3 times, with the amount of water used each time being twice that of the polymer, in order to remove the demulsifier, residual emulsifier and initiator. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final measured residual moisture was ≤5 w / w, and the product yield was 94.26%.

[0040] Example 2 (1) Pre-emulsification: Add 18 parts of emulsifier raw material to the emulsification kettle and stir for 30 minutes. After complete dissolution, add 300 parts of chloroprene and 200 parts of butadiene to the emulsification kettle in sequence. Stir at 1500-2000 rpm for 30 minutes to obtain a pre-emulsion. The emulsifier raw material is composed of the following parts by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium oleate in a mass ratio of 1.5:1. The nonionic emulsifier includes isotretinoin polyoxyethylene ether T08 and isotretinoin polyoxyethylene ether T12 in a mass ratio of 2:2. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 300 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 50-65℃. 2 parts of potassium persulfate initiator and 6 parts of water are added to the raw material. The mixture is stirred for 15 minutes to obtain a prepolymer emulsion. (3) Polymerization: The pre-emulsion obtained in step (1), 2 parts potassium sulfate initiator, 6 parts water, and 0.3 parts n-dodecyl mercaptan molecular weight regulator were simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure was controlled at 0.2-0.5 MPa, and after keeping warm for 5 hours, a polymerized emulsion was obtained with a solid content of 44.16%. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 1 part of water to stop the reaction; (5) Post-treatment: 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 60°C for 3 times, with the amount of water used each time being twice that of the polymer, in order to remove the demulsifier, residual emulsifier and initiator. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final measured residual moisture was ≤5 w / w, and the product yield was 93.87%.

[0041] Example 3 (1) Pre-emulsification: 20 parts of emulsifier raw materials sodium dodecyl sulfate and sodium oleate in a mass ratio of 1:2, and isotridecyl alcohol polyoxyethylene ether T08 and isotridecyl alcohol polyoxyethylene ether T12 in a mass ratio of 2:2 are added to an emulsification kettle and stirred for 30 minutes. After complete dissolution, 400 parts of chloroprene and 100 parts of butadiene are added to the emulsification kettle in sequence. After stirring at 1500-2000 rpm for 30 minutes, a pre-emulsion is obtained. The emulsifier raw materials are composed of the following parts by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium oleate in a mass ratio of 1:2, and the nonionic emulsifier includes isotridecyl alcohol polyoxyethylene ether T08 and isotridecyl alcohol polyoxyethylene ether T12 in a mass ratio of 2:2. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 200 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 50-65℃. 1 part of potassium persulfate initiator and 6 parts of water are added to the raw material. Stir for 10-20 minutes to obtain a prepolymer emulsion. (3) Polymerization: The pre-emulsion obtained in step (1), 2 parts potassium sulfate initiator, 6 parts water, and 0.2 parts n-dodecyl mercaptan molecular weight regulator were simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure was controlled at 0.2-0.5 MPa, and after keeping warm for 5 hours, a polymerized emulsion was obtained with a solid content of 46.62%. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 1 part of water to stop the reaction; (5) Post-treatment: 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 60°C for 3 times, with the amount of water used each time being twice that of the polymer, in order to remove the demulsifier, residual emulsifier and initiator. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final measured residual moisture was ≤5 w / w, and the product yield was 95.58%.

[0042] Comparative Example 1 (1) Pre-emulsification: Add 18 parts of emulsifier raw material to the emulsification kettle and stir for 30 minutes. After complete dissolution, add 300 parts of chloroprene and 200 parts of butadiene to the emulsification kettle in sequence. Stir at 1500-2000 rpm for 30 minutes to obtain a pre-emulsion. The emulsifier raw material is composed of the following parts by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium stearate in a mass ratio of 1:1. The nonionic emulsifier includes nonylphenol polyoxyethylene ether and oleyl alcohol polyether in a mass ratio of 2:2. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 300 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 50-65℃. 2 parts of potassium persulfate initiator and 6 parts of water are added to the raw material. Stir for 10-20 minutes to obtain a prepolymer emulsion. (3) Polymerization: The pre-emulsion obtained in step (1), 2 parts potassium sulfate initiator, 6 parts water, and 0.3 parts n-dodecyl mercaptan molecular weight regulator were simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure was controlled at 0.2-0.5 MPa, and after keeping warm for 5 hours, a polymerized emulsion was obtained with a solid content of 38.17%. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 1 part of water to stop the reaction; (5) Post-treatment: 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 60°C for 3 times, with the amount of water used each time being twice that of the polymer, in order to remove the demulsifier, residual emulsifier and initiator. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final measured residual moisture was ≤5 w / w, and the product yield was 87.54%.

[0043] Comparative Example 2 (1) Pre-emulsification: Add 18 parts of emulsifier raw material to the emulsification kettle and stir for 30 minutes. After complete dissolution, add 300 parts of chloroprene and 200 parts of butadiene to the emulsification kettle in sequence. Stir at 1500-2000 rpm for 30 minutes to obtain a pre-emulsion. The emulsifier raw material is composed of the following parts by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium oleate in a mass ratio of 1.5:1. The nonionic emulsifier includes isotretinoin polyoxyethylene ether T08 and isotretinoin polyoxyethylene ether T12 in a mass ratio of 2:2. (2) Polymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 300 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 50-65℃. Then, 4 parts of potassium persulfate initiator, 12 parts of water, and 0.3 parts of n-dodecyl mercaptan, a molecular weight regulator, are added in sequence. The mixture is stirred evenly with the pre-emulsion obtained in step (1). The reaction pressure is controlled at 0.2-0.5 MPa. After holding at the temperature for 5 hours, a polymer emulsion is obtained with a solid content of 34.98%. (3) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 1 part of water to stop the reaction; (4) Post-treatment: A 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 60°C three times, with the amount of water used each time being twice the amount of polymer, to remove demulsifiers, residual emulsifiers, and initiators. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final residual moisture content was ≤5 w / w%. The product yield was 85.20%.

[0044] Comparative Example 3 (1) Pre-emulsification: Add 20 parts of emulsifier raw material to the emulsification kettle and stir for 30 minutes. After complete dissolution, add 200 parts of chloroprene and 200 parts of butadiene to the emulsification kettle in sequence. Stir at 1500-2000 rpm for 30 minutes to obtain a pre-emulsion. The emulsifier raw material is composed of the following parts by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium oleate in a mass ratio of 1:1. The nonionic emulsifier includes isotridecyl alcohol polyoxyethylene ether T08 and isotridecyl alcohol polyoxyethylene ether T12 in a mass ratio of 2:1. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 400 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 40-50℃ (excluding 50℃). 1.5 parts of potassium persulfate initiator and 6 parts of water are added to the raw material. The mixture is stirred for 15 minutes to obtain a prepolymer emulsion. (3) Polymerization; The pre-emulsion obtained in step (1), 1 part potassium sulfate initiator, 4 parts water, and 0.1 part n-dodecyl mercaptan molecular weight regulator were simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure was controlled at 0.2-0.5 MPa, and after keeping warm for 5 hours, a polymerized emulsion was obtained with a solid content of 32.52%. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 2 parts of water to stop the reaction; (5) Post-treatment: A 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 50°C three times, with the amount of water used each time being twice the amount of polymer, to remove demulsifiers, residual emulsifiers, and initiators. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final residual moisture content was ≤5 w / w%. The product yield was 82.49%.

[0045] Comparative Example 4 (1) Pre-emulsification: Add 20 parts of emulsifier raw material to the emulsification kettle and stir for 30 minutes. After complete dissolution, add 200 parts of chloroprene and 200 parts of butadiene to the emulsification kettle in sequence. Stir at 1500-2000 rpm for 30 minutes to obtain a pre-emulsion. The emulsifier raw material is composed of the following parts by weight: 10 parts of anionic emulsifier, 18 parts of nonionic emulsifier, and 600 parts of deionized water. The anionic emulsifier includes sodium dodecyl sulfate and sodium oleate in a mass ratio of 1:1. The nonionic emulsifier includes isotridecyl alcohol polyoxyethylene ether T08 and isotridecyl alcohol polyoxyethylene ether T12 in a mass ratio of 2:1. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 400 parts of 2,3-dichlorobutadiene-1,3 monomer are added to the polymerization reactor. The temperature is controlled at 65-80℃ (excluding 65℃). 1 part of potassium persulfate initiator and 6 parts of water are added to the raw material. The mixture is stirred for 15 minutes to obtain a prepolymer emulsion. (3) Polymerization: The pre-emulsion obtained in step (1), 1 part potassium sulfate initiator, 4 parts water, and 0.1 part n-dodecyl mercaptan initiator are simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure is controlled at 0.2-0.5 MPa, and after keeping warm for 5 hours, a polymerized emulsion is obtained with a solid content of 35.17%. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature. Add 1 part of sodium bicarbonate as a buffer to adjust the pH of the emulsion to neutral, and add 1 part of tert-butylcatechol as a terminator and 2 parts of water to stop the reaction; (5) Post-treatment: A 5 w / w% calcium chloride solution was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water at 50°C three times, with the amount of water used each time being twice the amount of polymer, to remove demulsifiers, residual emulsifiers, and initiators. The washed polymer was dehydrated and dried by centrifugation for 10 min to obtain a powdered solid product. The final residual moisture content was ≤5 w / w%. The product yield was 81.36%.

[0046] Performance testing (1) Film preparation: After drying the copolymer obtained in the examples, compounding agents, including vulcanizing agents, accelerators, antioxidants, dispersants, and reinforcing agents, were added according to a certain formula ratio. Test pieces were obtained through mixing, vulcanization molding, and post-treatment. Examples 1, 2, and 3 correspond to test pieces 1, 2, and 3, respectively; Comparative Examples 1, 2, 3, and 4 correspond to test pieces 4, 5, 6, and 7, respectively.

[0047] (2) Mechanical property testing Table 1. Mechanical property test results Tests on specimens 1-3 showed high tensile strength, indicating strong intermolecular forces between chloroprene and the 2,3-dichloroprene-1,3 copolymer, resulting in good crosslinking density. The elongation at break and stress at 500% elongation were essentially equivalent, both demonstrating good physical and mechanical properties. Specimen 3 showed slightly higher Shore hardness at room temperature, likely due to a higher proportion of chloroprene during copolymerization.

[0048] Mechanical property tests revealed that samples 4-7 performed worse than samples 1-3. Specifically, the Mooney viscosity of samples 4-7 was generally increased, leading to decreased processing performance; simultaneously, the tensile strength also decreased. Notably, sample 6 showed a significantly increased elongation at break, indicating insufficient cross-linking density under low-temperature conditions, making molecular chains more prone to slippage. Sample 7 exhibited an abnormally high 500% elongation stress, primarily due to excessively high reaction temperature, which triggered over-cross-linking and thus rigidified the material.

[0049] (3) Characteristics of copolymers Table 2 Comparison of copolymer properties The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A method for preparing a copolymer of chloroprene and 2,3-dichlorobutadiene-1,3, characterized in that, The method includes the following steps: (1) Pre-emulsification: Add the emulsifier raw material to the emulsification tank and stir for 20-30 minutes. After it is completely dissolved, add a portion of the polymer raw material to the emulsification tank in sequence and stir for a set time to obtain the pre-emulsion. The emulsifier raw material is composed of the following parts by weight: 8-12 parts of anionic emulsifier, 16-20 parts of nonionic emulsifier, and 460-650 parts of deionized water. (2) Prepolymerization: Nitrogen gas is introduced into the polymerization reactor to replace oxygen. 2,3-Dichlorobutadiene-1,3 monomer is added to the polymerization reactor. The temperature is controlled at 50-65℃. Initiator raw materials are added and stirred for 10-20 minutes to obtain a prepolymer emulsion. (3) Polymerization: The pre-emulsion obtained in step (1), the initiator raw material and the molecular weight regulator are simultaneously added dropwise to the pre-polymerized emulsion obtained in step (2). The reaction pressure is controlled at 0.2-0.5 MPa, and the polymerized emulsion is obtained after keeping it at the temperature for 4-6 hours. (4) Termination of reaction: When the monomer conversion rate reaches the expected level, cool the reaction system to room temperature; add a buffer to adjust the pH of the emulsion to neutral, and add a terminator to stop the reaction; (5) Post-treatment: The demulsifier was added dropwise to the emulsion under stirring. The emulsion was washed with deionized water to remove the demulsifier, as well as the residual emulsifier and initiator. The washed polymer was dehydrated and dried by centrifugation. The final moisture content was measured to be ≤5%.

2. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (1), the anionic emulsifier is selected from at least one of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium stearate, calcium stearate, and sodium oleate; The anionic emulsifier is selected from at least one of sodium dodecyl sulfate, sodium alkylbenzene sulfonate, sodium stearate, calcium stearate, and sodium oleate; the nonionic emulsifier is selected from at least one of fatty alcohol polyoxyethylene ether, alkylphenol polyoxyethylene ether, and fatty acid polyoxyethylene ester.

3. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 2, characterized in that, The anionic emulsifier is a combination of sodium dodecyl sulfate and sodium oleate, with a mass ratio of sodium dodecyl sulfate to sodium oleate of (1-1.5):(1.5-2); the nonionic emulsifier is a fatty alcohol polyoxyethylene ether, which is a combination of isotridecyl alcohol polyoxyethylene ether T08 and isotridecyl alcohol polyoxyethylene ether T12, with a mass ratio of isotridecyl alcohol polyoxyethylene ether T08 to isotridecyl alcohol polyoxyethylene ether T12 of (2-3):(1-2).

4. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (1), the polymer raw material is composed of the following parts by weight: 200-400 parts of chloroprene and 100-225 parts of butadiene; In step (1), the stirring conditions are: stirring speed of 1500-2000 rpm and stirring time of 20-30 min.

5. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (2), during nitrogen purging, the gauge pressure is 0.05~0.2 MPa. The pressurization-depressurization cycle method is adopted, and the pressure is increased to 0.1 MPa and then depressurized to atmospheric pressure each time. The stirring speed is controlled at 500-800 rpm. In step (2), the 2,3-dichlorobutadiene-1,3 monomer is 200-400 parts by weight; In step (2), the initiator raw material is composed of the following parts by weight: 1-3 parts potassium persulfate and 4-6 parts water.

6. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (3), the dripping conditions are: dripping time is 3-4 hours and dripping temperature is 50-65℃; the initiator raw material is composed of the following parts by weight: potassium persulfate 1-4 parts, water 4-6 parts; the molecular weight regulator is n-dodecyl mercaptan 0.1-0.5 parts.

7. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (4), the buffer is 1-3 parts by weight of sodium bicarbonate; the terminator is composed of the following raw materials in parts by weight: 1-3 parts of tert-butylcatechol and 1-3 parts of water; when the reaction conversion rate reaches 90%, the buffer and terminator are added dropwise to the polymerization reactor at the same time and stirred for 20 minutes.

8. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (5), the demulsifier is a 5w / w%-10w / w% calcium chloride solution, and the amount of calcium chloride added is usually 1.0%~3.0% of the total weight of the emulsion; the stirring speed of the CaCl2 solution is controlled at 200~400 rpm, and the dropping speed is 1s / d.

9. The method for preparing the copolymer of chloroprene and 2,3-dichlorobutadiene-1,3 as described in claim 1, characterized in that, In step (5), deionized water at 50-60℃ is used for washing, and the amount of water is 2-3 times the mass of the wet polymer; washing is repeated 2-3 times; the speed of the centrifuge is controlled at 2000-3000 rpm, and centrifugation is carried out for 10-15 minutes.

10. The use of the method according to any one of claims 1 to 9 or the product obtained by the method according to any one of claims 1 to 9 in the preparation of chloroprene rubber.

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