A method for preparing high-elasticity chlorinated polyethylene by a gas-solid phase method

Abstract

The application provides a method for preparing high-elasticity chlorinated polyethylene by a gas-solid phase method, which comprises the following steps: adding polyethylene, a swelling agent and a dispersing agent into a reactor, and then introducing nitrogen gas to obtain an initial product with a chlorine content of 10-15%; obtaining an intermediate product with a chlorine content of 30-33%; and finally obtaining a product with a chlorine content of 33-38% under a process atmosphere. The method solves the problems of insufficient deep chlorination of particles in a low-temperature section and product adhesion in a high-temperature section, and obtains a product with uniform chlorination and high elasticity, thereby providing a scheme for realizing industrial production of high-elasticity chlorinated polyethylene prepared by the gas-solid phase method.

Description

Technical Field

[0001] This invention relates to a method for preparing highly elastic chlorinated polyethylene using a gas-solid phase method, and more particularly to a method for preparing highly elastic chlorinated polyethylene using a gas-solid phase method. Background Technology

[0002] Chlorinated polyethylene (CPE) is a random-structured polymeric synthetic material produced by the chlorination reaction of polyethylene. Depending on the chlorination conditions and chlorine content, it can be produced in forms ranging from rubbery to rigid plastic. As a novel polymeric elastomer and plastic modifying resin, CPE possesses excellent comprehensive properties. With the development of society and technology, its applications are becoming increasingly widespread, finding extensive use in plastic building materials, wires and cables, rubber processing, polymer flame retardant modification, and anti-corrosion coatings.

[0003] There are three main methods for preparing chlorinated polyethylene (CPE): solution method, suspension method, and solid-phase method. The solution method is highly polluting, requires significant investment, and is complex, and has been largely phased out. The suspension method is currently the mainstream process for CPE production and is relatively mature, but it generates a large amount of acidic wastewater, which no longer meets increasingly stringent environmental protection requirements. The solid-phase method is simple and less polluting, making it an environmentally friendly and economical new process. However, because the heat dissipation medium in the solid-phase reaction is gas, while in the suspension method it is liquid, the heat dissipation capacity of the gas phase is much weaker than that of the liquid phase. This means that the gas-solid phase reaction can only proceed at relatively low reaction temperatures or under relatively mild conditions. Once the temperature exceeds a certain limit, the product will agglomerate. The low reaction temperature and agglomeration result in poor chlorination uniformity and low elasticity in the product, thus limiting its applications. Some researchers have solved the high-temperature adhesion problem by adding quartz sand and using a segmented heating method (CN 109111534 A), but this method has the problem of quartz sand recycling and fails to solve the problem of uneven chlorination at low temperatures. This invention uses the addition of swelling agents and mixed dispersants to treat the raw materials, which effectively solves the problems of uneven chlorination at low temperatures and easy adhesion at high temperatures. The additives used do not need to be recycled and can be directly used for post-processing. Summary of the Invention

[0004] To address the problem of excessive chlorination of particles in the low-temperature stage and material adhesion in the high-temperature stage during the gas-solid phase preparation of chlorinated polyethylene, resulting in poor uniformity of chlorination and low elasticity of the particles, this invention provides a method for preparing highly elastic chlorinated polyethylene using the gas-solid phase method. This method has good controllability and produces a product with high elasticity.

[0005] A gas-solid phase method for preparing highly elastic chlorinated polyethylene includes pre-reaction, intermediate reaction, and final reaction processes, with the chlorination reaction carried out sequentially. Pre-reaction: A mixture including a swelling agent, an organic dispersant, and an inorganic dispersant is mixed with raw materials, nitrogen gas is introduced, and the temperature is raised to 60-90°C and held for a certain time. Then, process gas is introduced to obtain an initial product with a chlorine content of 10-15% by mass. Intermediate reaction: The initial product is heated to 100-140°C, and process gas is introduced to obtain an intermediate product with a chlorine content of 30-33% by mass. Final reaction: The temperature of the intermediate product is adjusted to 100-120°C, and under the process gas atmosphere, the chlorine content is increased until it reaches 33-38% by mass. The product is then sent to subsequent processing stages to obtain the highly elastic chlorinated polyethylene product. The aforementioned "certain time" refers to a holding time of 30-200 minutes.

[0006] As described above, in specific steps, step 1: Nitrogen gas is introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to remove air from the system. 100 parts of polyethylene raw material and 2-10 parts of organic dispersant are added to the reactor and mixed for 10-20 minutes. 5-10 parts of swelling agent are added, the temperature is raised to 60-80℃, and the mixture is stirred for 20-40 minutes. 10-20 parts of inorganic dispersant are added, the temperature is raised to 70-90℃, and the mixture is treated for 40-60 minutes to allow the particles to fully swell and the inorganic dispersant to uniformly coat the particle surface.

[0007] Step 2. Turn off the nitrogen gas, introduce the process gas, adjust the flow rate to 2.5% / min~3% / min, and perform the chlorination reaction at 80-100℃ for 60-80 min to obtain an initial product with a chlorine mass content of 10-15%. Step 3. Heat the initial product to 115-120℃ at a heating rate of 1.5-2.5℃ / min and chlorinate for 60-80 min. Then, continue heating to 120-130℃ at a heating rate of 1.0-1.5℃ / min and chlorinate for 40-60 min to obtain an intermediate product with a chlorine content of 30-33%.

[0008] Step 4. Adjust the temperature of the intermediate product to 100-120℃ at a rate of 1.0-1.5℃ / min, and react for 60-80 min in the process gas atmosphere to obtain a product with a chlorine mass content of 33-38%, which is then sent to the subsequent processing stage to obtain a high-elasticity chlorinated polyethylene product with an elongation at break greater than 800%.

[0009] As mentioned above, the swelling agents include phthalates, or one or more of epoxidized soybean oil and solid paraffin.

[0010] As mentioned above, phthalic acid esters include: dioctyl phthalate, monomethyl phthalate, dioctyl phthalate, diallyl phthalate, etc.

[0011] As described above, the organic dispersant includes one or more of ethylene oxide-propylene oxide block copolymers, polyvinyl alcohol, and sodium polyacrylate.

[0012] As mentioned above, inorganic dispersants include one or more of magnesium oxide, silicon oxide, talc, calcium carbonate, and fumed silica.

[0013] As mentioned above, the particle size of the inorganic dispersant is between 150-245 μm.

[0014] As mentioned above, the ratio of organic dispersant to inorganic dispersant is 1:1 to 1:3.

[0015] As mentioned above, the process gas flow rate is adjusted according to the amount of raw material input, and its range is that the mass of the process gas is 2.5-3% of the mass of the raw material.

[0016] As mentioned above, the pre-reaction heating rate is 1.5-2.5℃ / min, the intermediate reaction heating rate is 1.5-2.5℃ / min, and the final reaction heating rate is 1.0-2.0℃ / min.

[0017] As mentioned above, the process gas is a mixture of chlorine, nitrogen, and hydrogen chloride.

[0018] This invention first adds an organic dispersant to the raw materials to form a protective film on the particle surface, preventing particle adhesion after pretreatment and heating. Then, a swelling agent is added, and the temperature is increased until the polyethylene resin particles are fully swollen, ensuring sufficient expansion of the internal pores. This facilitates the rapid entry of chlorine free radicals into the particle interior after chlorination, allowing the chlorination reaction to occur simultaneously inside and outside the particle, improving chlorination uniformity. Finally, an inorganic dispersant is added, and the temperature is further increased until the particle skin softens, allowing the inorganic dispersant to be evenly coated onto the surface of the polyethylene resin particles, preventing particle adhesion during the subsequent high-temperature chlorination process. The reaction is carried out in three stages: pre-reaction, intermediate reaction, and final reaction. Pre-treated resin particles undergo a pre-reaction, where the chlorination reaction mainly occurs on the particle surface and internal pores, reinforcing the particle pores and surface strength to prevent collapse of the internal pores during the later high-temperature reaction, which would hinder the entry of chlorine free radicals. The pre-treated product is then sent to an intermediate reactor for deep chlorination. Once the reaction temperature reaches the crystallization melting temperature, particle adhesion will not occur. As the chlorine content increases, the crystals are gradually broken down, and the melting temperature decreases. By further heating above the melting point, the remaining crystals are destroyed, and the particles become elastic. Subsequent high-temperature heat treatment causes the molecular chain segments on the surface and inside of the particles to shift, further improving the uniformity of chlorination in the product. Ultimately, a chlorinated polyethylene product with good elasticity is obtained, with an elongation at break ≥800%.

[0019] For every chlorine atom added to the polyethylene molecular chain, one hydrogen atom is replaced, producing one hydrogen chloride molecule. The mass change of the polyethylene molecular chain is 34.5, and the mass of the hydrogen chloride is 36.5. Therefore, the chlorine content of chlorinated polyethylene can be calculated quantitatively based on the weight gain of saturated brine. The calculation formula is shown below, where ΔW is the weight of HCl produced in the chlorination reaction, and W is the weight of the polyethylene raw material used in the chlorination reaction.

[0020] CL%=[(ΔW*34.5 / 36.5) / (W+ΔW*34.5 / 36.5)]*100 The tail gas produced by the chlorination reaction mainly consists of hydrogen chloride gas and unreacted chlorine gas. The hydrogen chloride gas in the tail gas can be removed by saturated brine, and the remaining unabsorbed pure chlorine gas in the tail gas can be dried and reused.

[0021] The swelling agent used in the chlorination reaction is one or more of phthalic acid esters, epoxidized soybean oil, and solid paraffin; the dispersant used is one or more of light calcium carbonate and ethylene oxide-propylene oxide block copolymer.

[0022] The method described above is suitable for preparing chlorinated polyethylene with a chlorine content of 30-38% by mass.

[0023] The beneficial effects of this invention are as follows: By combining the addition of a swelling agent and heat treatment, the particles are fully expanded, ensuring that the number of chlorine free radicals inside and outside the particles is as consistent as possible. This results in a more uniform chlorine distribution in the product during the chlorination reaction, guaranteeing chlorination uniformity at the microscopic level. Simultaneously, the addition of a mixing dispersant prevents the particles from agglomerating during high-temperature reactions, ensuring chlorination uniformity at the macroscopic level and further increasing particle elasticity.

[0024] This invention pretreats resin particles by adding swelling agents and composite dispersants, which achieves microscopic chlorination uniformity and avoids particle adhesion and agglomeration, ensuring macroscopic chlorination uniformity. The two treatments greatly improve particle elasticity. Subsequently, through pre-reaction, intermediate reaction and final reaction, a highly elastic product is obtained. The performance indicators of the product are basically consistent with those of the product prepared by the acid phase method, which meets the standards for industrialization. Implementation

[0025] The present invention is further illustrated below through specific embodiments. All contents are calculated by mass and are mass content; the parts are measured by mass and are parts by mass. The main industrial requirements for CPE products prepared by the acid phase method are: chlorine content 30%-40%, heat of melt ≤2J / g, Shore hardness ≤65, tensile strength ≥8MPa, elongation at break ≥600%, volatile content ≤0.3%, thermal stability time ≥8min, and combustion residue ≤4.5%.

[0026] The main indicators of the chlorinated polyethylene product prepared by the present invention are: chlorine content of 35% to 42%, melting enthalpy ≤ 2 J / g, thermal stability time ≥ 600 s, combustion residue < 3%, volatile content < 0.3%, hardness of 50 to 65, tensile strength of 8 to 10 MPa, and elongation at break of 750% to 850%.

[0027] Example 1: Nitrogen gas was introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. 100 parts of polyethylene raw material and 10 parts of organic dispersant polyvinyl alcohol were added to the reactor and mixed at room temperature for 10 min. Then, 10 parts of swelling agent epoxidized soybean oil were added, the temperature was raised to 60°C, and the mixture was stirred for 20 min. Next, 10 parts of inorganic dispersant calcium carbonate with a particle size of 150 μm were added, the temperature was raised to 85°C, and the mixture was stirred for 30 min. The nitrogen gas was then turned off, and process gas was introduced at a flow rate of 2.5% / min. The reaction was carried out at 85°C for 60 min, completing the pre-chlorination reaction. The product from the pre-reactor was transferred to the intermediate reaction reactor, and the temperature was increased to 113°C at a rate of 1.5°C / min. The chlorination reaction was carried out for 80 min. The temperature was then increased to 120°C at a rate of 1.5°C / min, and the high-temperature chlorination reaction was carried out for 60 min, completing the intermediate reaction. The product prepared in the intermediate reactor is transferred to the final reactor. Under a process gas atmosphere, the heat treatment temperature is set to 110℃ and the heat treatment time is 60 minutes. After heat treatment, the nitrogen valve is opened and the process gas valve is closed to purge the process gas from the system. The process gas absorbs hydrogen chloride gas through saturated brine and unreacted chlorine gas through sodium hydroxide solution. Once the reactor temperature drops to room temperature, the chlorinated polyethylene product is removed, washed with alkaline solution until neutral, and then dried in an oven to constant weight.

[0028] The difference between Example 2 and Example 1 is that 20 parts of calcium carbonate with a particle size of 150 μm were added.

[0029] The difference between Example 3 and Example 1 is that 30 parts of calcium carbonate with a particle size of 150 μm were added.

[0030] Example 4 differs from Example 1 in that 20 parts of calcium carbonate with a particle size of 245 μm are added.

[0031] Example 5: Nitrogen gas was introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. 100 parts of polyethylene raw material and 10 parts of organic dispersant polyvinyl alcohol were added to the reactor and mixed at room temperature for 10 min. 10 parts of swelling agent solid paraffin were added, and the temperature was raised to 60°C and mixed for 20 min. 20 parts of inorganic dispersant calcium carbonate with a particle size of 150 μm were added, and the temperature was raised to 85°C and mixed for 30 min. The nitrogen gas was then turned off, and process gas was introduced at a flow rate of 2.5% / min. The reaction was carried out at 85°C for 60 min, completing the pre-chlorination reaction. The product from the pre-reactor was transferred to the intermediate reaction reactor, and the temperature was increased to 113°C at a rate of 1.5°C / min, with a chlorination reaction lasting 80 min. The temperature was then increased further at a rate of 1.5°C / min to 120°C, with a high-temperature chlorination reaction lasting 60 min, completing the intermediate reaction. The product prepared in the intermediate reactor is transferred to the final reactor. Under a process gas atmosphere, the heat treatment temperature is set to 110℃ and the heat treatment time is 60 minutes. After heat treatment, the nitrogen valve is opened and the process gas valve is closed to purge the process gas from the system. The process gas absorbs hydrogen chloride gas through saturated brine and unreacted chlorine gas through sodium hydroxide solution. Once the reactor temperature drops to room temperature, the chlorinated polyethylene product is removed, washed with alkaline solution until neutral, and then dried in an oven to constant weight.

[0032] The difference between Example 6 and Example 5 is that solid paraffin is added and the mixing time is extended to 40 minutes after heating.

[0033] The difference between Example 7 and Example 5 is that solid paraffin is added, and the mixing temperature is raised to 70°C after heating.

[0034] The difference between Example 8 and Example 5 is that solid paraffin is replaced with dioctyl phthalate.

[0035] The difference between Example 9 and Example 8 is that after adding dioctyl phthalate, the mixing temperature is increased to 85°C.

[0036] The difference between Example 10 and Example 9 is that after adding dioctyl phthalate, the mixing temperature was increased to 90°C.

[0037] The difference between Example 11 and Example 5 is that ethylene oxide-propylene oxide block copolymer is used instead of polyvinyl alcohol.

[0038] Example 12: Nitrogen gas was introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. 100 parts of polyethylene raw material and 10 parts of ethylene oxide-propylene oxide block copolymer were added to the reactor and mixed at room temperature for 10 min. Then, 10 parts of solid paraffin were added, the temperature was raised to 70°C, and the mixture was stirred for 20 min. Next, 20 parts of calcium carbonate with a particle size of 150 μm were added, the temperature was raised to 85°C, and the mixture was stirred for 30 min. The nitrogen gas was then turned off, and process gas was introduced at a flow rate of 2.5% / min. The reaction was carried out at 85°C for 60 min, completing the pre-chlorination reaction. The product from the pre-reactor was transferred to the intermediate reaction reactor, and the temperature was increased to 115°C at a rate of 1.5°C / min, with a chlorination reaction lasting 80 min. The temperature was then increased further at a rate of 1.5°C / min to 125°C, with a high-temperature chlorination reaction lasting 60 min, completing the intermediate reaction. The product prepared in the intermediate reactor was transferred to the final reactor, and under a process gas atmosphere, a heat treatment temperature of 110°C was set for 60 min. After heat treatment, open the nitrogen valve and close the process gas valve to purge the process gas from the system. The process gas absorbs hydrogen chloride gas through saturated brine and unreacted chlorine gas through sodium hydroxide solution. Once the reactor temperature drops to room temperature, remove the chlorinated polyethylene product, wash it with alkaline solution until neutral, and then dry it in an oven to constant weight.

[0039] Example 13: Nitrogen gas was introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. 100 parts of polyethylene raw material and 10 parts of polyvinyl alcohol were added to the reactor and mixed at room temperature for 10 min. Then, 10 parts of solid paraffin were added, the temperature was raised to 70℃, and the mixture was stirred for 20 min. Next, 20 parts of calcium carbonate with a particle size of 150 μm were added, the temperature was raised to 85℃, and the mixture was stirred for 40 min. The nitrogen gas was then turned off, and process gas was introduced at a flow rate of 2.5% / min. The reaction was carried out at 85℃ for 60 min, completing the pre-chlorination reaction. The product from the pre-reactor was transferred to the intermediate reaction reactor, and the temperature was increased to 115℃ at a rate of 1.5℃ / min, with a chlorination reaction lasting 80 min. The temperature was then increased further at a rate of 1.5℃ / min to 125℃, with a high-temperature chlorination reaction lasting 60 min, completing the intermediate reaction. The product prepared in the intermediate reactor was transferred to the final reactor, and under a process gas atmosphere, a heat treatment temperature of 110℃ was set for 60 min. After heat treatment, open the nitrogen valve and close the process gas valve to purge the process gas from the system. The process gas absorbs hydrogen chloride gas through saturated brine and unreacted chlorine gas through sodium hydroxide solution. Once the reactor temperature drops to room temperature, remove the chlorinated polyethylene product, wash it with alkaline solution until neutral, and then dry it in an oven to constant weight.

[0040] Example 14: Nitrogen gas was introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. 100 parts of polyethylene raw material and 10 parts of polyvinyl alcohol were added to the reactor and mixed at room temperature for 10 min. 10 parts of epoxidized soybean oil were added, and the temperature was raised to 60°C and mixed for 20 min. 20 parts of calcium carbonate with a particle size of 150 μm were added, and the temperature was raised to 85°C and mixed for 30 min. The nitrogen gas was then turned off, and process gas was introduced at a flow rate of 2.5% / min. The reaction was carried out at 85°C for 60 min, completing the pre-chlorination reaction. The product from the pre-reactor was transferred to the intermediate reaction reactor, and the temperature was increased to 113°C at a rate of 1.5°C / min, with a chlorination reaction for 80 min. The temperature was then increased to 130°C at a rate of 1.5°C / min, with a high-temperature chlorination reaction for 60 min, completing the intermediate reaction. The product prepared in the intermediate reactor was transferred to the final reactor, and under a process gas atmosphere, a heat treatment temperature of 110°C was set for 60 min. After heat treatment, open the nitrogen valve and close the process gas valve to purge the process gas from the system. The process gas absorbs hydrogen chloride gas through saturated brine and unreacted chlorine gas through sodium hydroxide solution. Once the reactor temperature drops to room temperature, remove the chlorinated polyethylene product, wash it with alkaline solution until neutral, and then dry it in an oven to constant weight.

[0041] Example 15: Nitrogen gas was introduced into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. 100 parts of polyethylene raw material and 10 parts of polyvinyl alcohol were added to the reactor and mixed at room temperature for 10 min. 10 parts of dioctyl phthalate were added, and the mixture was heated to 85°C and mixed for 30 min. 20 parts of calcium carbonate with a particle size of 150 μm were added, and the mixture was mixed at 85°C for 30 min. The nitrogen gas was then turned off, and process gas was introduced at a flow rate of 2.5% / min. The reaction was carried out at 85°C for 60 min, completing the pre-chlorination reaction. The product from the pre-reactor was transferred to the intermediate reaction reactor, and the temperature was increased to 113°C at a rate of 1.5°C / min. The chlorination reaction was carried out for 80 min. The temperature was then increased to 130°C at a rate of 1.5°C / min, and the high-temperature chlorination reaction was carried out for 60 min, completing the intermediate reaction. The product prepared in the intermediate reactor was transferred to the final reactor, and under a process gas atmosphere, the heat treatment temperature was set to 110°C for 60 min. After heat treatment, open the nitrogen valve and close the process gas valve to purge the process gas from the system. The process gas absorbs hydrogen chloride gas through saturated brine and unreacted chlorine gas through sodium hydroxide solution. Once the reactor temperature drops to room temperature, remove the chlorinated polyethylene product, wash it with alkaline solution until neutral, and then dry it in an oven to constant weight.

Claims

1. A method for preparing highly elastic chlorinated polyethylene via a gas-solid phase process, characterized in that, The steps are as follows: Step 1: Introduce nitrogen into the gas-solid phase method reaction system for preparing highly elastic chlorinated polyethylene to purge air from the system. Add 100 parts of polyethylene raw material and 2-10 parts of organic dispersant to the reactor and mix for 10-20 minutes. Add 5-10 parts of swelling agent, heat to 60-80℃, and mix for 20-40 minutes. Add 10-20 parts of inorganic dispersant, heat to 70-90℃, and treat for 40-60 minutes to fully swell the particles and uniformly coat the particle surface with inorganic dispersant. Step 2: Turn off the nitrogen gas, introduce the process gas, adjust the flow rate to 2.5% / min~3% / min, and carry out the chlorination reaction at 80-100℃ for 60-80 min to obtain an initial product with a chlorine mass content of 10-15%. Step 3: The initial product is heated to 115-120℃ at a heating rate of 1.5-2.5℃ / min and chlorinated for 60-80 min. Then, the temperature is increased to 120-130℃ at a heating rate of 1.0-1.5℃ / min and chlorinated at high temperature for 40-60 min to obtain an intermediate product with a chlorine mass content of 30-33%. Step 4: Adjust the temperature of the intermediate product to 100-120℃ at a rate of 1.0-1.5℃ / min, and react for 60-80 minutes in the process gas atmosphere to obtain a product with a chlorine content of 33-38% by mass. This product is then sent to the subsequent processing stage to obtain highly elastic chlorinated polyethylene.

2. The method according to claim 1, characterized in that: Swelling agents include one or more of phthalates, epoxidized soybean oil, and solid paraffin.

3. The method according to claim 1, characterized in that: Organic dispersants include one or more of the following: ethylene oxide-propylene oxide block copolymer, polyvinyl alcohol, and sodium polyacrylate.

4. The method according to claim 1, characterized in that: Inorganic dispersants include one or more of magnesium oxide, silicon oxide, talc, and calcium carbonate.

5. The method according to claim 4, characterized in that: The particle size of the inorganic dispersant is between 150-245 μm.

6. The method according to claim 1, characterized in that: The ratio of organic dispersant to inorganic dispersant is 1:1 to 1:

3.

7. The method according to claim 1, characterized in that: The process gas flow rate is adjusted according to the amount of raw material input, and its range is 2.5-3% of the raw material mass.