Ethylene propylene rubber (EPR) is a kind of ethylene rubber after the invention of Ziegler-Natta catalyst and the appearance of polyethylene and polypropylene. * * * Polypropylene rubber with propylene as the basic monomer can be divided into two categories: EPDM and EPDM. The former is a polymer of ethylene and propylene; The latter is a copolymer of ethylene, propylene and a small amount of unconjugated diene. Ethylene propylene rubber has many excellent properties that other general synthetic rubber does not have. In addition, the monomer is cheap and easy to obtain, and has a wide range of uses. It is the fastest growing of seven synthetic rubber varieties abroad since 1980s, and its output, capacity and consumption rank third in developed countries, second only to styrene-butadiene rubber and cis-butadiene rubber. 1998 The total global EPR production capacity is about 102 tons, and the consumption is 8 14000 tons. According to preliminary statistics, the consumption of1000 tons in 1999 is about 836 1000 tons, and it is expected to reach 980,000 tons in 2003. From 1998 to 2003, the demand growth rate of EPDM was 3.8%, which was higher than that of SBR and BR.
At present, there are three industrial production processes of FPR: solution polymerization, suspension polymerization and gas phase polymerization. The following will discuss its technical situation and remaining points in detail, and make a technical and economic comparison.
1, solution polymerization process
Technical status of 1. 1
Industrialization was realized in the early 1960s. After continuous improvement and perfection, the technology has matured and been used by many newly built devices. It is the dominant technology in industrial production, accounting for about 77.6% of the total production capacity of FPR.
This process is a homogeneous reaction in a solvent that can dissolve the product, monomer and catalyst system. Usually, linear alkanes such as n-hexane are used as solvents, and V-A 1 catalyst system is adopted. The polymerization temperature is 30 ~ 50C, the polymerization pressure is 0.4 ~ 0.8 MPa, and the mass fraction of polymer in the reaction product is generally 8% ~ 10%. The technological process basically consists of raw material preparation, chemical preparation, polymerization, catalyst removal, monomer and solvent recovery and refining, coagulation, drying and polymerization.
Packaging and other processes, but because each company has its own patented technology in a certain part or control, it has its own unique process realization method. The representative companies are DSM, Exxon, uniroya 1, DuPont, Mitsui Petrochemical Company of Japan and JSR Company. The most typical one is DSM company, which is not only the largest EPR producer in the world, but also four plants in the Netherlands, the United States, Japan and Brazil all adopt solution polymerization process, accounting for 1/4 of the total production capacity of EPR by solution polymerization process in the world. Take this company as an example.
DSM takes hexane as the solvent, ethylidene norbornene (ENB) or dicyclopentadiene (DCPD) as the third monomer, hydrogen as the molecular weight regulator, and VOCL3- 1/2Al2O3 as the catalyst. In addition, in order to improve the activity of the catalyst and reduce its dosage, an accelerator was added. The proportion and dosage of catalyst, pretreatment method and accelerator type are the proprietary technology of DSM company. The reaction materials are precooled to 500℃, and one kettle or two kettles are operated in series according to the production brand. The volume of the polymerizer is about 6m3. The polymerization conditions are as follows: the temperature is lower than 65℃, the pressure is lower than 2.5MPa, and the reaction heat is used for adiabatic heating of the reactor. Under the action of alkaline vanadium removal agent and hot water, the residual vanadium catalyst in polymer glue solution enters the water phase and is completely removed through two phase inversion processes. Unreacted monomer is recovered and recycled by secondary decompression flash evaporation. At this time, additives such as stabilizers are added to the glue solution (oil-filled brands are added when producing oil-filled brands). Residual ethylene, propylene and most solvents were distilled by stripping.
The skimmed liquid is sent to two coagulation kettles in series for coagulation, and the remaining hexane solvent is further distilled and recovered. JC colloidal slurry enters the drying system after dehydration, and then is packaged into blocks or powders. The waste hot air containing ENB is sent to the incinerator for incineration, and the vanadium-containing sewage is sent to the sewage vanadium removal unit. Under the neutralization and flocculation of vanadium removal agent, vanadium enters vanadium slag, which is sent to landfill regularly, and the sewage after vanadium removal is discharged into sewage treatment plant for treatment.
The EPR solution polymerization technology of DSM company is mature and advanced, which has the following advantages:
(1) Less investment and optimized process. The optimum proportion design of the reactor can meet the requirements of reaction material mixing, and can accurately control the polymerization process parameters and product quality. The concentration of polymer glue solution is high, but the amount of circulating solvent is small, the polymerization kettle is small, but the production intensity is high, raw materials and circulating monomers do not need to be refined, the catalyst efficiency is high, the vanadium content in the three wastes is low, and the yield elasticity is high.
(2) The production and operation cost is low, the annual operation time of the device is long, the consumption of raw materials and accelerators is low, and the advanced control system is adopted to control the production.
(3) The product quality is very competitive. The product has the advantages of low catalyst residue content, less defective products in production, flexible product brand switching, less waste products, adjustable product characteristics according to user's requirements, many product brands, adjustable Mooney value in a wide range of 20 ~ 160, stable quality, good repeatability, narrow product specification range and excellent product processability.
Technical characteristics of 1.2
Mature technology and stable operation are the main methods of industrial production of ethylene-propylene rubber. There are many varieties and brands of products, uniform quality, less ash and wide application range; The product has good electrical insulation performance. However, because the polymerization is carried out in a solvent, the mass transfer and heat transfer are limited, and the mass fraction of polymer is generally controlled at 6% ~ 9%, and the highest is only 1 1% ~ 14%, so the polymerization efficiency is low. At the same time, because the solvent needs to be recovered and refined, the production process is long, there are many equipments, and the construction investment and operation cost are high.
2. Suspension polymerization process
2. 1 technical status
EPR suspension polymerization process has few brands and limited uses. Mainly used for polyolefin modification. At present, it is only used by Enichem Company and Bayer Company, accounting for 65,438+03.4% of the total EPR capacity. Based on the principle of low activity of propylene in * * * polymerization, this process dissolves ethylene in liquid propylene for * * * polymerization. Propylene is both a monomer and a reaction medium, and the reaction temperature and pressure are controlled by its own evaporation and refrigeration. The generated polymer is insoluble in liquid propylene, but exists in the form of fine slurry suspended therein. It can also be divided into general suspension polymerization process and simplified suspension polymerization process.
2. 1. 1 general suspension polymerization process
Enichem Company adopts this process: vanadium acetylacetonate and AlEt2Cl are used as catalysts, diethyl dichloromalonate is used as activator, HNB or DCPD is used as the third monomer, and diethyl zinc and hydrogen are used as molecular weight regulators. According to the brand of the products produced, ethylene, propylene, the third monomer and the catalyst are added into a jacketed polymerization kettle with a multi-blade agitator, and the reaction conditions are: the temperature is 20-20℃, the pressure is 0.35-65438 0.05 MPa, and the reaction heat is removed by evaporation of the monomer in the reaction phase. The mass fraction of suspended polymer in the reaction phase is controlled between 30% and 35%, and the whole polymerization reaction is carried out under highly automatic control. The generated polymer propylene slurry is intermittently sent to the scrubber (10 ~ 15 times /h), and the catalyst is deactivated with polypropylene glycol, and then washed with NaOH aqueous solution. The suspension is sent to the stripper for stripping, and the unreacted ethylene, propylene and ENB are refined by the recovery system and recycled. The colloidal particle-water slurry is dehydrated by vibrating screen, extruded and dried, and packed in blocks to obtain the finished adhesive. The process is characterized by high polymer concentration and no solvent, which improves the production capacity of equipment, saves solvent circulation and recovery and saves energy.
2. 1.2 Simplified suspension polymerization process
The process was successfully developed on the basis of the general suspension polymerization process, mainly using high-efficiency titanium-based catalytic system, without removing the catalyst, and the unreacted monomer can be reused without treatment. It is usually used to produce EPM, because it is not easy to remove unreacted third monomer by flash evaporation. The technological process is as follows: the reaction is carried out in a stirred tank with a jacket, with TiC 1, MgC 12-A 1(i-Bu) as the catalytic system, the catalytic efficiency is 50kg polymer /g titanium, the reaction temperature is 27C, the pressure is 1.3MPa, and the polymer mass fraction. The steam material from the reaction kettle is compressed to 2.7MPa and returned to the reaction kettle after cooling. Unreacted monomers are removed from the polymer slurry by flash evaporation without refining treatment, and are directly recycled to the reaction kettle after compression and cooling. The monomer-removed polymer can be used as a finished product without purification. The product can be powder, flake or granule. In recent years, Enichem Company has adopted an improved V-A 1 catalytic system, and the catalyst efficiency has been increased to 30 ~ 50 kg polymer /g vanadium, thus eliminating the washing and catalyst removal processes and simplifying the process flow.
2.2 technical characteristics
The characteristics of EPR suspension polymerization process are: the polymer product is insoluble in propylene, the viscosity of the system is low, the conversion rate is improved, and the mass fraction of polymer is as high as 30% ~ 35%, so its production capacity is 4 ~ 5 times that of solution method; No solvent recovery, refining and coagulation process, simplified process flow and less capital investment; Can produce very high molecular weight varieties; The product cost is lower than that of solution method. However, its disadvantages are: it is difficult to separate the residual catalyst from the polymer because no solvent is used; product
Few varieties and brands, poor quality uniformity and high ash content; Polymers are suspended particles insoluble in liquid propylene, so it is difficult to keep them in suspension, especially when the polymer concentration is high and a small amount of gel appears, the reactor is easy to get stuck or even block the equipment pipeline. The electrical insulation performance of the product is poor.
3. Gas phase polymerization process
3. 1 technical status
The gas phase polymerization process of EPR was first industrialized by Himont Company in the late 1980s. In the early 1990s, UCC Company announced that the pilot plant of gas phase EPR was put into production, and its 9 10000 tons/year industrial plant of gas phase EPR was officially put into production on 1999. At present, this process accounts for 9% of the total EPR capacity. The EPR gas phase polymerization process of UCC company is the most representative, which is divided into three processes: polymerization, separation and purification and packaging. 60% ethylene, 35.5% propylene, 4.5% ENB, catalyst, hydrogen, nitrogen and carbon black were added into a fluidized bed reactor, and gas phase polymerization was carried out at 50 ~ 65℃ and 2.07kPa absolute pressure. The single-pass conversion rate of ethylene, propylene and ENB was 5.2% respectively. 0.58% and 0.4%. The unreacted monomer from the reactor is compressed by the recycle gas compressor, then enters the recycle gas cooler to remove the reaction heat, and is recycled back to the reactor together with the fresh feed gas. EPR powder discharged from the reactor enters the purification tower without degassing and decompression, and the residual hydrocarbons are removed by nitrogen. The gas from the top of the purification tower is condensed to recover the ENB, and then pumped back to a specific bed reactor. The produced granular products enter the packaging process.
3.2 Technical Features
Compared with the first two processes, gas phase polymerization process has its outstanding advantages: the process flow is short, with only three processes, while the traditional process has seven processes; No solvent or diluent is needed, and no solvent recovery and refining steps are needed; There is almost no three warm emissions, which is beneficial to ecology.
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