High-strength chlorosulfonated polyethylene and method for producing the same

Abstract

The application belongs to the technical field of polymer materials, and specifically discloses a high-strength chlorosulfonated polyethylene and a preparation method thereof, which comprises the following steps: S1, chlorinated polyethylene, a dispersing agent and an initiator are added into a reaction container and stirred uniformly at room temperature; S2, nitrogen is introduced into the reaction container to remove residual gas in the container; S3, a sulfuryl chloride solution is slowly added into the reaction system, and the feeding time is controlled to be 1 h to 1.5 h; S4, the reaction system is heated and maintained at a certain temperature, and constant-temperature reaction is carried out for 4 h to 5 h; and S5, the product after reaction is washed by a solvent and dried to obtain modified chlorosulfonated polyethylene. The application adopts a liquid-solid phase reaction system, discards the traditional suspension solvent idea, directly uses sulfuryl chloride to simultaneously undertake the functions of a reaction reagent and a liquid-phase dispersing medium, only causes a single-step chlorosulfonation reaction, is simple and convenient to operate, is environmentally friendly, and the tensile strength of the obtained product can reach more than 30 MPa.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a method for preparing high-strength chlorosulfonated polyethylene via a liquid-solid phase synthesis. Background Technology

[0002] Chlorosulfonated polyethylene (CSM) is a special saturated synthetic rubber obtained by chlorination and chlorosulfonation graft modification of the polyethylene main chain. Its molecular main chain is a fully saturated carbon chain, and the side chains are regularly introduced with chlorine atoms and chlorosulfonyl active groups (-SO2Cl). It combines the excellent weather resistance, ozone resistance, and heat aging resistance of saturated rubber with the oil resistance, chemical corrosion resistance, flame retardancy, and interfacial adhesion properties imparted by polar groups. It is widely used in automotive rubber seals, flame-retardant wire and cable sheaths, anti-corrosion linings for chemical equipment, and building waterproof membranes, and is one of the irreplaceable key special materials in the field of high-end engineering rubber.

[0003] Currently, the industrial preparation technology of chlorosulfonated polyethylene mainly falls into two major categories: solution method and gas-solid phase method. The solution method uses halogenated hydrocarbons such as carbon tetrachloride and tetrachloroethylene as reaction solvents. After the polyethylene is completely dissolved to form a homogeneous system, a mixture of chlorine and sulfur dioxide is introduced, or sulfonyl chloride reagent is added dropwise. Under the action of a free radical initiator, the chlorosulfonation grafting reaction is completed. This process uses large amounts of ozone-depleting substances such as carbon tetrachloride, resulting in significant environmental pressure; solvent recovery is energy-intensive, and the product is prone to solvent residue, affecting processing performance. The gas-solid phase method uses solid polyethylene or chlorinated polyethylene particles as raw materials. Chlorine and sulfur dioxide are introduced into a fluidized bed reactor for reaction, completely eliminating the use of organic solvents. However, the gas-solid mass transfer resistance is high, and the chlorosulfonation reaction mainly concentrates on the particle surface, easily leading to a concentration gradient of "excessive chlorosulfonation on the surface and insufficient reaction inside," which affects the improvement of mechanical properties.

[0004] Chinese patent application CN104725534A discloses a suspension method for preparing chlorosulfonated polyethylene. This method uses inert compounds such as carbonates or phosphate esters as suspension solvents, suspending chlorinated polyethylene powder in a large amount of this solvent to achieve the chlorosulfonation reaction. However, this process still relies on a large amount of suspension solvent (0.5 to 10 times the mass of the chlorinated polyethylene powder), resulting in high energy consumption for solvent recovery and purification. Furthermore, the large amount of solvent occupies the effective volume of the reaction vessel, leading to poor equipment volume efficiency and limited single-vessel capacity. Simultaneously, the reaction requires the addition of pyridine as a catalyst, which is a toxic compound, posing a risk of toxic residues in the product. In addition, the process uses a one-time addition of sulfonyl chloride, resulting in concentrated reaction heat, making it difficult to achieve a breakthrough improvement in the mechanical properties of the product.

[0005] Due to limitations in the preparation process, the mechanical properties of existing commercially available chlorosulfonated polyethylene (CSM) suffer from significant bottlenecks. The tensile strength of ordinary industrial-grade CSM vulcanizates is typically 8–18 MPa, while the tensile strength of industrial products vulcanized using the gas-solid phase method is mostly concentrated in the 10–20 MPa range. Therefore, developing a method for preparing high-strength chlorosulfonated polyethylene with a green and environmentally friendly process and excellent mechanical strength is of significant industrial application value. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the technical problem this invention aims to solve is to provide a liquid-solid phase method for synthesizing high-strength chlorosulfonated polyethylene. This method abandons the traditional suspension solvent approach, using finished chlorinated polyethylene as a base, and directly employing sulfonyl chloride to simultaneously serve as both a reaction reagent and a liquid-phase dispersion medium. Only a single-step chlorosulfonation reaction occurs, making the operation simple, environmentally friendly, and yielding a product with a tensile strength exceeding 30 MPa.

[0007] To solve the above-mentioned technical problems, the technical solution of the present invention is as follows: A method for preparing high-strength chlorosulfonated polyethylene, using finished chlorinated polyethylene as a base, synthesizes chlorosulfonated polyethylene via a liquid-solid phase method, comprising the following steps: S1. At room temperature, chlorinated polyethylene, dispersant and initiator are added to a reaction vessel and stirred until homogeneous. The mass ratio of the dispersant, initiator and chlorinated polyethylene is (1.5-3):(0.5-2.5):100. S2. Purge the reaction vessel with nitrogen gas to remove residual gas from the vessel. S3. Slowly add sulfonyl chloride solution to the reaction system, controlling the addition time to be 1 h to 1.5 h; based on pure sulfonyl chloride, the amount of sulfonyl chloride added is 35% to 65% of the mass of the chlorinated polyethylene; S4. Heat the reaction system to 70 ℃~80 ℃ and maintain the temperature at this temperature for 4 h~5 h. S5. The product after the reaction is washed with solvent and then dried to obtain the modified chlorosulfonated polyethylene.

[0008] The sulfonation process of chlorinated polyethylene is shown in the following formula: Preferably, in step S1, the chlorine content of the chlorinated polyethylene is 25% to 45%.

[0009] Preferably, in step S1, the dispersant is selected from one or more of the following: modified hydrophobic silica (D17), calcium stearate, sodium dodecylbenzene sulfonate, and polyoxyethylene ethers, in any proportion, with D17 being the most preferred.

[0010] Preferably, in step S1, the initiator is selected from one or more of lauroyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, and azobisisobutyronitrile in any proportion, with lauroyl peroxide being the most preferred. This invention initiates the free radical reaction solely through heat, eliminating the need for toxic catalytic aids such as pyridine, thus avoiding the problem of toxic substance residues.

[0011] Preferably, in step S3, the amount of sulfonyl chloride added is 45% to 60% of the mass of the chlorinated polyethylene. This invention employs a slow dropwise addition process of 1 to 1.5 hours to add sulfonyl chloride to the reaction system, effectively avoiding concentrated reaction heat and localized overheating, making the chlorosulfonation reaction mild and controllable, and inhibiting the degradation of the polymer molecular chains.

[0012] Preferably, in step S5, the washing is carried out in stages: first, a low-carbon fatty alcohol is used for pre-washing to remove oil-soluble impurities, then a dilute alkaline aqueous solution is used for neutralization and washing, and finally, deionized water is used for rinsing until neutral.

[0013] Preferably, the low-carbon fatty alcohol is anhydrous ethanol or isopropanol; the dilute alkaline aqueous solution is a sodium bicarbonate aqueous solution with a mass fraction of 0.5% to 2% or a sodium carbonate aqueous solution with a mass fraction of 0.3% to 1%.

[0014] Preferably, in the pre-washing with low-carbon fatty alcohol, the amount of anhydrous ethanol or isopropanol is 1.2 to 1.5 times the product mass, and the washing time is 15 to 20 minutes; in the neutralization washing with dilute alkaline aqueous solution, the amount of alkaline solution is 1.8 to 2.0 times the product mass, and the washing time is 15 to 20 minutes; in the rinsing with deionized water, the amount of deionized water is 2.0 to 2.5 times the product mass, and the rinsing is repeated until the pH of the washing solution is 7.0 to 7.5.

[0015] Preferably, in step S5, the drying temperature is 50 ℃~60 ℃ and the drying time is 6 h~12 h.

[0016] The high-strength chlorosulfonated polyethylene prepared by the above method has a vulcanized rubber tensile strength ≥30 MPa and an elongation at break ≥465%.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: (1) This invention adopts a liquid-solid phase reaction system, abandoning the traditional suspension solvent approach, and directly using sulfonyl chloride to simultaneously serve as both a reaction reagent and a liquid phase dispersion medium. Compared with the traditional solution method, this invention does not use ozone-depleting solvents such as carbon tetrachloride throughout the entire process, thus avoiding the environmental hazards of the traditional solution method from the source. The amount of post-treatment solvent used is small and easy to recover, and the amount of waste emissions is low, which meets the requirements of green chemical production. Compared with the suspension method, this invention does not require the use of a large amount of inert suspension solvent, saving the investment in solvent recovery and purification, and avoiding the problem of a large amount of solvent occupying the effective volume of the reaction vessel, which significantly improves the single-vessel capacity and equipment utilization efficiency.

[0018] (2) The present invention stabilizes the solid-liquid dispersion system through a dispersant, effectively inhibits the agglomeration of chlorinated polyethylene particles, and enables sulfonyl chloride to fully and uniformly contact the particle surface. The chlorosulfonation reaction is carried out simultaneously at the liquid-solid interface. The chlorine and sulfur elements in the product are evenly distributed, the chlorosulfonyl active groups are neatly grafted, and the crosslinking points are well dispersed, laying a structural foundation for improving mechanical properties.

[0019] (3) The chlorosulfonated polyethylene synthesized by the liquid-solid method of this invention has a uniform distribution of crosslinking points. The slow dripping process of sulfonyl chloride effectively avoids local overheating and heat concentration caused by one-time feeding. The chlorine content can be precisely controlled in advance by the chlorinated polyethylene raw material. The chlorosulfonation reaction is mild and controllable, effectively inhibiting the degradation of polymer molecular chains. The obtained chlorosulfonated polyethylene vulcanizate has a tensile strength of up to 32 MPa and an elongation at break of ≥500%, with outstanding mechanical properties that are far superior to the conventional level of existing industrial products.

[0020] (4) This invention does not require the addition of toxic catalysts such as pyridine. It completes chlorosulfonation only through thermally initiated free radical reaction. There are no toxic catalyst residues in the product, and it is highly safe to use.

[0021] (5) The process of this invention is simple to operate and the post-processing process is short. It does not require a complex fluidized bed reaction system and tail gas circulation treatment device. The equipment investment is significantly lower than that of the traditional gas-solid phase fluidized bed process, which effectively improves the overall economic efficiency of chlorosulfonated polyethylene production and has broad market application prospects and industrial promotion value. Attached Figure Description

[0022] The following figures are intended only to illustrate and explain the present invention and do not limit the scope of the invention. Wherein: Figure 1 This is a comparison of the infrared spectra of chlorinated polyethylene and the resulting chlorosulfonated polyethylene in Example 1 of this invention. Detailed Implementation

[0023] The present invention will be further described below with reference to the accompanying drawings and embodiments. In the following detailed description, only certain exemplary embodiments of the invention are described by way of illustration. Undoubtedly, those skilled in the art will recognize that various modifications can be made to the described embodiments without departing from the spirit and scope of the invention. Therefore, the drawings and description are illustrative in nature and not intended to limit the scope of the claims.

[0024] Example 1 At room temperature, 300 kg of chlorinated polyethylene (CPE, 35% chlorine content, powder, average particle size 150 μm), 5.1 kg of modified hydrophobic silica (D17), and 3 kg of lauroyl peroxide were added to a 3000 L glass-lined reactor. A double-layer stirring system (an anchor-type bottom layer and a slanted paddle-type top layer) was started, with the stirring speed controlled at 80–100 r / min. The mixture was stirred and dispersed for 30 min until a homogeneous powder mixture was formed. The reactor was then sealed, and a vacuum pump was started to evacuate the reactor to a pressure ≤ -0.09 MPa. After maintaining this pressure for 5 min, high-purity nitrogen was introduced to a slightly positive pressure (gauge pressure 0.02 MPa). This vacuum-nitrogen purging operation was repeated three times to ensure that the oxygen content inside the reactor was below 50 ppm.

[0025] 111 kg of sulfonyl chloride (pure sulfonyl chloride, 37% of the CPE mass) was added at multiple points using a ring-shaped spray method on the top of the reactor, ensuring uniform spraying across the entire powder bed surface. The addition time was controlled to 1 h, during which the stirring speed was maintained at 100 r / min. After the sulfonyl chloride addition was complete, the material in the reactor was heated to 75±1 ℃ at a heating rate of 1.5 ℃ / min, and the reaction was maintained at this temperature for 4 h. During the reaction, the reactor pressure was maintained at 0.05–0.10 MPa (nitrogen protection pressure).

[0026] After the reaction was completed, stirring was stopped, and the material in the reactor was discharged and transferred to a three-stage washing tank for further processing: The first stage involved pre-washing with anhydrous ethanol (1.5 times the product mass, stirred and washed at room temperature for 20 min, then centrifuged); the second stage involved neutralization and washing with a 2% sodium bicarbonate aqueous solution (2 times the product mass, stirred and washed at room temperature for 15 min, then centrifuged); and the third stage involved rinsing with deionized water (2.5 times the product mass, stirred and washed at room temperature for 15 min, then centrifuged). The third rinsing stage was repeated until the pH of the washing solution reached 7.0–7.5. The centrifuged wet material was then transferred to a double-cone rotary vacuum dryer, with the drying temperature controlled at 50±2 ℃, vacuum degree ≤-0.08 MPa, and drying time at 12 h. After discharge, the material was passed through a 40-mesh vibrating sieve to obtain chlorosulfonated polyethylene powder.

[0027] Example 2 The procedure was the same as in Example 1, except that the amount of sulfonyl chloride added was changed to 138 kg (46% of the mass of CPE), the dropping time was 1.2 h, the reaction temperature was 75±1 ℃, and the reaction time was 4 h.

[0028] Example 3 The procedure was the same as in Example 1, except that the amount of sulfonyl chloride added was changed to 174 kg (58% of the mass of CPE), the dropping time was 1.3 h, the reaction temperature was 75±1 ℃, and the reaction time was 4 h.

[0029] Example 4 The procedure was the same as in Example 1, except that the amount of sulfonyl chloride added was changed to 195 kg (65% of the mass of CPE), the dropping time was 1.5 h, the reaction temperature was 75±1 ℃, and the reaction time was 4 h.

[0030] Example 5 The operating equipment and process parameters are the same as in Example 1, except that the chlorinated polyethylene base is replaced with CPE (powder, average particle size 130 μm) with a chlorine content of 45%, the feed amount is 300 kg, the amount of sulfonyl chloride added is adjusted to 52% of the mass of CPE (i.e. 156 kg), the dripping time is 1.3 h, the reaction temperature is 75 ℃, and the reaction time is 4 h.

[0031] Example 6 The operating equipment and process parameters are the same as in Example 1, except that the modified hydrophobic silica is replaced with sodium dodecylbenzenesulfonate, lauroyl peroxide is replaced with tert-butyl peroxide, the amount of sulfonyl chloride added is 111 kg, the dropping time is 1 h, the reaction temperature is 75±1 ℃, and the reaction time is 4 h.

[0032] refer to Figure 1 A comparative analysis of the infrared spectra of chlorinated polyethylene and the resulting chlorosulfonated polyethylene in Example 1 showed that the infrared spectra were 1367 cm⁻¹. -1 (characteristic absorption of -SO2Cl) and 1162 cm⁻¹ -1 A distinct new absorption peak appears at the (S=O symmetric stretching vibration) location, proving that the chlorosulfonyl group was successfully grafted.

[0033] The structural formula of the obtained chlorosulfonated polyethylene is as follows: The properties of chlorosulfonated polyethylene after vulcanization in Examples 1 to 6 were tested according to the method specified in GB / T 30920-2014, and the indicators are as follows: As can be seen from the table above, the chlorosulfonated polyethylene prepared by the method of the present invention in Examples 1 to 6 has a tensile strength of 30 to 32.21 MPa and an elongation at break of 471 to 531%. Its elasticity and processing performance meet the application requirements of special rubbers and are far superior to the conventional levels of existing gas-solid phase industrial products and traditional solution-based high-end grades. This fully demonstrates the technical advantages of the liquid phase process of the present invention in preparing high-strength chlorosulfonated polyethylene.

[0034] Among them, when the amount of sulfonyl chloride added is 58% of the mass of CPE (Example 3), the product has the best comprehensive mechanical properties and the tensile strength can reach 32.21 MPa.

[0035] Example 5 further verifies that the method is also applicable to substrates with high chlorine content (45%), and the tensile strength remains above 31 MPa.

[0036] In Example 6, sodium dodecylbenzenesulfonate was used instead of modified hydrophobic silica, and tert-butyl peroxide was used instead of lauroyl peroxide. The reaction was still successfully completed under the same process conditions, indicating that the liquid-solid phase reaction system constructed in this invention has a wide range of compatibility with dispersants and initiators and good process robustness.

[0037] In summary, this invention employs a liquid-solid phase reaction system, abandoning the traditional approach of using suspension solvents. Sulfonyl chloride directly serves as both a reaction reagent and a liquid-phase dispersion medium. Compared to traditional solution methods, this invention eliminates the use of ozone-depleting solvents such as carbon tetrachloride, avoiding the environmental hazards of traditional solution methods from the source. It also reduces the amount of solvent used in post-treatment, making it easy to recycle and resulting in low emissions of waste gas, wastewater, and solid waste, meeting the requirements of green chemical production. Compared to suspension methods, this invention eliminates the need for large amounts of inert suspension solvents, saving on solvent recovery and purification costs. It also avoids the problem of large amounts of solvent occupying the effective volume of the reaction vessel, significantly improving single-vessel capacity and equipment utilization efficiency.

[0038] The above description is merely an illustrative embodiment of the present invention and is not intended to limit the scope of the invention. Any equivalent changes and modifications made by those skilled in the art without departing from the concept and principles of the present invention should fall within the scope of protection of the present invention.

Claims

1. A method for preparing high-strength chlorosulfonated polyethylene, characterized in that, Using finished chlorinated polyethylene as a base, chlorosulfonated polyethylene is synthesized via a liquid-solid phase method, comprising the following steps: S1. At room temperature, chlorinated polyethylene, dispersant and initiator are added to a reaction vessel and stirred until homogeneous. The mass ratio of the dispersant, initiator and chlorinated polyethylene is (1.5-3):(0.5-2.5):

100. S2. Purge the reaction vessel with nitrogen gas to remove residual gas from the vessel. S3. Slowly add sulfonyl chloride solution to the reaction system, controlling the addition time to be 1 h to 1.5 h; based on pure sulfonyl chloride, the amount of sulfonyl chloride added is 35% to 65% of the mass of the chlorinated polyethylene; S4. Heat the reaction system to 70 ℃~80 ℃ and maintain the temperature at this temperature for 4 h~5 h. S5. The product after the reaction is washed with solvent and then dried to obtain the modified chlorosulfonated polyethylene.

2. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 1, characterized in that: The chlorine content of the chlorinated polyethylene in step S1 is 25% to 45%.

3. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 1, characterized in that: In step S1, the dispersant is selected from one or more of the following: modified hydrophobic silica, calcium stearate, sodium dodecylbenzene sulfonate, and polyoxyethylene ethers, in any proportion.

4. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 1, characterized in that: In step S1, the initiator is selected from one or more of lauroyl peroxide, benzoyl peroxide, di-tert-butyl peroxide, tert-butyl peroxide, and azobisisobutyronitrile in any proportion.

5. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 1, characterized in that: In step S3, the amount of sulfonyl chloride added is 45% to 60% of the mass of the chlorinated polyethylene.

6. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 1, characterized in that: In step S5, the washing is carried out in stages: first, low-carbon fatty alcohol is used for pre-washing to remove oil-soluble impurities, then dilute alkaline aqueous solution is used for neutralization and washing, and finally deionized water is used for rinsing until neutral.

7. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 6, characterized in that: The low-carbon fatty alcohol is anhydrous ethanol or isopropanol; the dilute alkaline aqueous solution is a sodium bicarbonate aqueous solution with a mass fraction of 0.5% to 2% or a sodium carbonate aqueous solution with a mass fraction of 0.3% to 1%.

8. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 7, characterized in that: In the pre-washing with low-carbon fatty alcohols, the amount of anhydrous ethanol or isopropanol used is 1.2 to 1.5 times the product mass, and the washing time is 15 to 20 minutes; in the neutralization washing with dilute alkaline aqueous solution, the amount of alkaline solution used is 1.8 to 2.0 times the product mass, and the washing time is 15 to 20 minutes; in the rinsing with deionized water, the amount of deionized water used is 2.0 to 2.5 times the product mass, and the rinsing is repeated until the pH value of the washing solution is 7.0 to 7.

5.

9. The method for preparing high-strength chlorosulfonated polyethylene as described in claim 1, characterized in that: In step S5, the drying temperature is 50 ℃~60 ℃, and the drying time is 6 h~12 h.

10. A high-strength chlorosulfonated polyethylene, characterized in that, The vulcanizate prepared by any one of claims 1 to 9 has a tensile strength ≥30 MPa and an elongation at break ≥465%.

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