CN101495224B - Loop type reactor for polymerization - Google Patents

Abstract

A process which comprises polymerising an olefin monomer in at least one continuous tubular loop reactor of a multiple reactor system, optionally together with an olefin comonomer, in the presence of a polymerisation catalyst in a diluent to produce a slurry comprising solid particulate olefin polymer and diluent, wherein the average internal diameter of at least 50% of the total length of the continuous tubular loop reactor is at least 700mm.

Description

The loop type reactor that is used for polymerization

The present invention relates in slurry phase circulation reactor, the particularly olefinic polymerization in the multiple reactor system.

The slurry phase polymerisation of alkene is well-known, wherein olefinic monomer and optional olefin comonomer, in the situation that in the thinner, exist catalyzer to be aggregated, wherein solid polymer product is suspended in described thinner and is transferred.

The present invention is specifically related to the polymerization at least one loop reactor of multiple reactor system, and wherein slurry is recycled by pump or agitator in reactor usually.The loop reactor (liquid full loop reactor) that is full of liquid is especially well-known in the art, and is described in United States Patent (USP) for example the 3rd, 152, No. 872, the 3rd, 242, No. 150 and the 4th, 613, No. 484.

Polyreaction is usually 50-125 ℃ temperature with carry out under the pressure of 1-100 bars absolute (bara).Used catalyzer can be any catalyzer that is generally used for olefinic polymerization, for example chromium oxide catalyst, Ziegler-Natta catalyst or metallocene-type catalyst.Comprise polymkeric substance and the thinner product slurry of (and in most of the cases comprising catalyzer, olefinic monomer and comonomer), can be discharged off and on or continuously, randomly use concentrating unit, for example hydrocyclone or settling leg (settling legs) are come so that the quantity that is recovered the fluid of (withdrawn) with polymkeric substance minimizes.

Described at least one loop reactor of multiple reactor system is continuous tubular structure, and it comprises at least two (for example four) vertical components and at least two (for example four) horizontal components.Usually utilize the heat of removing polymerization with the indirect exchange of heat-eliminating medium (preferably water) in the sleeve pipe of small part tubular ring flow reactor.The variable volume of at least one loop reactor of multiple reactor system, but usually 10 to 120m ³Scope, loop reactor of the present invention namely is this common type.

Maximum commercial scale loop reactor shop equipment throughput stably increases every year.Decades, ever-increasing operating experience was so that can operate more and more higher slurry and monomer concentration in reaction loop recently.Set forth such as EP 432555 and EP 891990, the increase of slurry concentration is normally realized by the speed of circulation that increases, and the increase of speed of circulation is to be realized by for example higher reactor cycles pumping head or a plurality of recycle pump.For the fixed reactor volume, the increase of solid loadings is favourable for increasing reactor residence time, and also is favourable for the requirement that reduces downstream diluent treatment and recirculation.But the speed of the increase of circulation and pressure head (head) requirement causes along with slurry concentration increases pump size and complicacy, and the increase of energy expenditure.This is hinting the increase of cost of capital and running cost.

In the past, usually in reaction loop, keep higher speed of circulation, to guarantee that good heat distribution, composition on the whole reactor cross-section distribute and particle distribution, particularly guarantee to avoid solid precipitation, stable flow performance or at the high solid concentration of crossing at tube wall place, rather than reduce speed of circulation so that the pressure drop/minimum power in the polymerization circulation.

Inadequate cross-sectional distribution can cause dirt increase, heat transfer minimizing and polymer yield and homogeneity to reduce.Make up and the new business equipment of going into operation very expensive, so new design attempts to avoid or minimize the change to operating parameters, the change of operating parameters is counted as increases the risk that new installation successfully operates.

According to the present invention, it provides a kind of method, the method is included at least one loop reactor of continuous tubular structure of multiple reactor system, in thinner, in the situation that there is polymerizing catalyst, with the olefinic monomer polymerization, randomly with olefinic monomer with the olefin comonomer polymerization, the slurry that comprises solid particulate olefin polymer and thinner with generation, wherein at least 50% of the reactor overall length mean inside diameter is at least 700 millimeters, and the solids concn in the reactor is at least 20 volume %, preferred 25 volume %, randomly the volume of wherein said at least one loop reactor is 10m at least ³, preferred 25m at least ³Preferred at least 30wt%'s, most preferably more than the polymkeric substance that in the multiple reactor system, generates of 40wt%, at least one loop reactor, make, wherein at least 50% of the reactor overall length mean inside diameter is at least 700 millimeters.

An advantage of the invention is, the specific energy consumption of loop reactor (specific energy consumption) (namely, the energy that the polymkeric substance of every generation unit weight consumes) is reduced, keeps simultaneously specific reactor residence time and prevent unacceptable reactor dirt.(be considered to need to use think now too high circulation cycle speed) when wanting to design and operate the reactor of high solids loadings, the present invention has superiority especially before.

The present invention relates to method and the instrument of successive polymerization alkene in the tubular closed loop reaction zone of elongation (preferred alpha's monoolefine).Alkene is joined continuously in the catalyzer in hydrocarbon diluent (hydrocarbon diluent) and with catalyzer and is contacted.Monomer polymerization is to form the slurry of solid particulate polymkeric substance, and described solid particulate polymkeric substance is suspended in polymerisation medium or the thinner.

Usually, in poly slurry polymerization process, the slurry in the reactor will comprise granular polymer, hydrocarbon diluent, (copolymerization) monomer, catalyzer, chain terminator (for example hydrogen) and other reactor additives.Especially, slurry will comprise the 20-75 that accounts for the slurry gross weight, the granular polymer of preferred 30-70 weight percentage and the 80-25 that accounts for the slurry gross weight, the suspension medium of preferred 70-30 weight percentage, wherein suspension medium is the summation of all fluid compositions (fluid components) in reactor, and will comprise thinner, olefinic monomer and any additive; Thinner can be that inert diluent or it can be reactive thinner (particularly liquid olefin monomers); Wherein main thinner is inert diluent, and olefinic monomer will account for the 2-20 of slurry usually, preferred 4-10 weight percentage.

Keep polymer suspension to keep the fluid velocity of acceptable cross section concentration and solid loading gradient in slurry neutralization (ii) to be enough to (i), pump into slurry around (path-endless) relatively level and smooth, that the path is endless circulation reactive system.

Find, for high solids loadings, cross-sectional slurry concentration distribution (being confirmed by dirt, mobile variation and/or heat transfer) can be maintained in the acceptable operational limits, increase simultaneously the internal diameter of tubular reactor, making it is reliable internal diameter (at least one reactor of multiple reactor system) greater than usually being considered in operation.Condition situation about thinking (internal diameter of reactor be not more than 600 millimeters and be generally approximately 500 millimeters) is opposite according to conventional methods with those skilled in the art for this.

Solids concn in the slurry at least one loop reactor preferably is at least 20 volume %, at least 25 volume % more preferably, and most preferably be at least 30 volume %, wherein volume % is [(volume of slurry cumulative volume-suspension medium)/(slurry cumulative volume)] * 100.The solids concn (it equates with the solids concn of measuring with the percent by volume form) of measuring with the weight percentage form will change according to the polymkeric substance that is produced, but more particularly, will change according to used thinner.When the polymkeric substance that produces is that polyethylene and thinner are when being alkane (for example Trimethylmethane), preferably, solids concn be greater than the slurry gross weight 30 % by weight, particularly preferably greater than 40 % by weight, for example in the scope of 40-60 % by weight, preferred 45%-55 % by weight.

We find, at least one reactor has in the multiple reactor system reactor of the conventional reactor larger diameter of using in slurry polymerization (namely than) of the internal diameter that surpasses 700 millimeters the operation polymerization process without any significant problem, particularly without any the problem about the dirt on reactor wall therein.

The overall length that is preferably greater than 50% loop reactor has the internal diameter above 750mm, for example surpasses 850mm, and preferably between 700 to 800 millimeters.Preferably, greater than 50%, particularly greater than 70%, for example have greater than 85% reactor overall length and surpass 700 millimeters internal diameter, particularly surpass 750 millimeters, for example between 700 to 800 millimeters.

Special advantage of the present invention is, can be under relatively low speed of circulation and relative high reactor loop diameters condition the high slurry concentration of use.Therefore, the Fu Laode in the reactor (Froude) number preferably be maintained at 30 or below, for example in 24 to 0.5 scope, more preferably in 20 to 1 scope, in 15 to 2 scope, most preferred scope is 10 to 3 or 9 to 2 in particular.Froude number is non-dimensional parameter, the suspension tendency of particle and the balance between the precipitation tendency in its indication slurry.It provides and the fluid-phase ratio, by the relative measurement of particle to the momentum transfer process of tube wall.The Froude number of low numerical value shows that stronger particle-wall (with respect to fluid-wall) interacts.Froude number (Fr) is defined as v ²/ (g (s-1) D), wherein v is the V-bar of slurry, and g is universal gravitational constant, and s is the proportion of solid in the thinner, and D is the internal diameter of pipe.The proportion of solid polymer (ratio of the density of polymkeric substance and the density of suspension medium) is based on by abundant devolatilization (devolatilised) afterwards and the annealed density of the degassed polymkeric substance before being about to carry out any extruding, and using method ISO 1183A measures.

Find, can per unit reactor length and the specific pressure drop of per unit polymer quality, and design and the operant response device less than the desired circulation total pressure drop of instruction, particularly when high solids loadings and large reactor diameter.Even be greater than per hour 25 tonnes for polymer-through-out rate, even greater than per hour 45 tonnes, the present invention also allows the general circulation pressure drop less than 1.3 bars absolute, particularly less than 1 bars absolute.Can in circulation, use one or a more than pump, be preferably placed on one or more horizontal components; These can be positioned on the identical horizontal component or distinct portions.Pump or a plurality of pump can have the diameter identical with the reactor internal diameter partly at described pump or a plurality of pumps place, or larger or less diameter, preferably have identical diameter.The single pump of preferred use, and characteristics of the present invention are do not have ordinary method to bother like that (onerous) for the quantity of pump and the requirement of power.

Reactor size surpasses 10m usually ³, often surpass 25m ³, especially surpass 50m ³, 75-200m for example ³, preferably at 100-175m ³Scope.

The reactor of higher internal diameter is used at least one loop reactor of the above-described multiple reactor of this paper system, so that the reactor that builds, for example volume is greater than 80m ³Reactor, the ratio of its reactor length and diameter preferably less than 400, is more preferably less than 250 less than 500.Reducing so that minimize around the component gradient of reaction loop of the ratio of reactor length and diameter, and so that for every kind of reagent, only use single introducing point can reach productivity greater than per hour (each reactor) 25 tonnes around reactor loop.Perhaps, for reactant (for example alkene), catalyzer or other additives, can have a plurality of entrances that enter loop reactor.

When reactor assembly is designed to operate different catalysts type (for example Ziegler-Natta, chromium and/or metallocenes) or the operation catalyst system that wherein required activity or output ratio (production ratio) alter a great deal between the lower different reactor of different operation modes (regime), usually use the reactor with equal volume, adapt to whole level range (grade range) with the handiness (flexibility) of maximum.The existence of (externally imposed) reactor size that force such outside has retrained the available action pane of each reactor, thereby has retrained the balanced capacity of reactor activity, product quality, output and cooling in each reactor.Usually, preferred like this reactor has identical mean inside diameter, and most preferably, reactor is constructed to identical size.

In another embodiment of the present invention, preferably, loop reactor has horizontal component and vertical component, and vertical component accounts at least 50% of reactor overall length, and preferably at least 60%, more preferably at least 70%.

Further preferably, the density span of polymeric powder particles (density span) (granularity that is defined as discharging reactor greater than the mean density of the polymer beads of D90 and granularity less than density difference (g/cm between the mean density of the material of D10 ³) absolute value) be less than 0.005, preferably less than 0.003, be more preferably less than 0.0026, most preferably less than 0.0023.

Therefore, another independent aspects of the present invention is provided in the situation that has polymerizing catalyst, the method of control slurry phase (being total to) polymerization process, be characterised in that described method comprises that the density span with polymeric powder particles maintains below 0.005, preferred below 0.003, more preferably below 0.0026, most preferably below 0.0023.

The D value is measured by sieve size assay method (sieving granulometry), and represents with μ m, and can be defined as foloows:

The particle that is collected of D5:5% weight is lower than this value;

The particle that is collected of D10:10% weight is lower than this value;

The particle that is collected of D50:50% weight is lower than this value;

The particle that is collected of D90:90% weight is lower than this value;

The particle that is collected of D95:95% weight is lower than this value.

Preferred embodiment also keep such size-grade distribution, itself so that (D90-D10)/D50 is less than 2, preferably less than 1.5, is more preferably less than 1.2.Further preferably, D95 is less than 2000 μ m, preferably less than 1500 μ m, be more preferably less than 1000 μ m, most preferably less than 355 μ m, wherein D95, D90, D50 and D10 are defined like this: it is so that the polymer beads of 95wt%, 90wt%, 50wt% or 10wt% has respectively the diameter less than D95, D90, D50 and D10.Mean particle size D 50 is preferably between 100 to 1500 microns, most preferably between 150 to 1000 microns.

The size-grade distribution that particularly preferred embodiment has be D95 less than 355 μ m, and (D90-D10)/D50 is less than 1.2, wherein D95, D90, D50 and D10 are as mentioned above.

Another independent aspects of the present invention provides a kind of method, it is included in the loop reactor of continuous tubular structure, in the situation that in the thinner, have polymerizing catalyst, with the olefinic monomer polymerization, randomly with olefinic monomer with the olefin comonomer polymerization, the slurry that comprises solid particulate olefin polymer and thinner with generation, wherein at least 50% of the reactor overall length mean inside diameter is at least 650 millimeters, and the solids concn in the reactor is at least 15 volume % and size-grade distribution so that (D90-D10)/and D50 is less than 2.

Another independent aspects of the present invention provide a kind of in polymerization reactor the method for olefin polymerization, be characterised in that the polymer powder that from reactor, reclaims size-grade distribution so that D95 less than 1500 μ m and (D90-D10)/D50 is less than 1.5.

According to another preferred implementation of the present invention, found described control, be about to density span and maintain below the particular value, very crucial for metalloscene catalyst.

Another benefit of the present invention is to have improved speed and the security relevant with starting (start-ups) and level transitions (grade transitions).When changing grade, composition and the product characteristics of hydrogen and monomer change serially, and the product characteristics that the absorption quantity of monomer will be changed again in the polymkeric substance (mainly being density) and gaseous constituent change.

According to the control of span of the present invention so that improved the speed that starts and change, and so that the production of (wide-specification) material of wide in range specification minimize.

Particularly find, high capacity reactors, the particularly stable operation of major diameter loop reactor, can optimize by the density span of the powder that reclaims in the strict control reactor or from reactor.

Use many catalyst systems, density span can significantly change with granularity and/or size-grade distribution.The main determining factor of the mean particle size of powder is the residence time and the catalyst production in reactor.The size-grade distribution of powder can be subjected to many factor affecting, comprise the soundness (robustness) of the type that joins the catalyzer in the reactor and size-grade distribution, initial and average catalyst activity, support of the catalyst and under reaction conditions powder to the susceptibility of fragment (fragment).The slurry that solid separating device (for example hydrocyclone) can be used to reclaim from reactor is with mean particle size and the size-grade distribution of powder in the subcontrol reactor.Design and the operational condition of the position in the recovery site of concentrating unit and concentrating unit system (preferably at least one hydrocyclone recirculation circulation), also so that reactor in granularity and size-grade distribution controlled.

Perhaps, select to be found to provide the special catalyst of the size-grade distribution of wanting.Provide the advantage of the catalyst system of the size-grade distribution of wanting to be, they can high yield be used: normal yield (grams with every g polymerization catalyst thing is measured) is higher, and formed single polymer beads is larger.So the present invention allows to use productive rate to be 5000g polyolefine/g catalyzer at least, and is generally at least 10000g polyolefine/g catalyzer, most preferably is the catalyst system greater than 15000g polyolefine/g catalyzer.

Use the prepolymer with controlled particle size distribution of any above-mentioned catalyzer manufacturing also can be introduced in the polymerization reactor.Polymerization can be undertaken by any suitable method, for example, utilizes batch process, semi-continuous process or continuous processing, the polymerization in the liquefied hydrocarbon thinner or in gas phase.Conversion to prepolymer is undertaken by catalyzer is contacted with one or more alpha's alkene usually, and the amount of alpha's alkene is so that every gram prepolymer contains the transition metal of 0.002 to 10 mmole.Prepolymer particle size can be by screening, hydrocyclone is meticulous or oarse-grained elutriation separates, or other known technologies are controlled.

Comprise in the embodiments of the present invention of multiple reactor system (one of them reactor is loop reactor) at these and other, loop reactor can have the characteristics of one or more loop reactors as discussed herein above.Second of the multiple reactor system or any follow-up reactor can be another loop reactor or any reactor for olefinic polymerization, for example fluidized-bed reactor.But preferably, second of the multiple reactor system or any follow-up reactor are another loop reactors, and it can have or not have the characteristics of one or more loop reactors as discussed herein above.For example, at least 50% of its length of loop reactor of the present invention can have the internal diameter greater than 700 millimeters, and second of while or any follow-up loop reactor can have greater than 500 millimeters, for example greater than 600 millimeters, are preferably greater than 700 millimeters internal diameter.

The multiple reactor system can be used to make unimodal (monomodal) polymkeric substance or multimodal (multimodal) polymkeric substance, preferred multimodal polymer.Preferably, method of the present invention comprises makes the multimodal ethylene polymkeric substance, bimodal ethylene particularly, wherein lower molecular weight (LMW) polymkeric substance is manufactured in a reactor, and high molecular (HMW) polymkeric substance is manufactured in another reactor, polymkeric substance is can any order manufactured, and second polymer is in the situation that exist the first polymkeric substance manufactured.One of them reactor or two reactors have at least internal diameter of 700mm along at least 50% of its length.

In an embodiment of the invention, the method in the multiple reactor system comprises that manufacturing density is greater than 940kg/m ³And melt flow index MI ⁵Be 0.05 to 50g/10 minute multimodal ethylene polymkeric substance, described ethene polymers comprises:

Account for the ethene polymers gross weight 30 to 70wt%, density is at least 950kg/m ³And melt flow index MI ₂Be at least the first polyethylene part (fraction) of 10g/10 minute, and

Account for the second polyethylene part of 70 to 30wt% of multimodal ethylene total polymer weight, described the second polyethylene portions is divided and is comprised ethylene unit and at least a other alpha's alkene that contain 3 to 12 carbon atoms of 5 % by mole at the most randomly, and melt flow index MI ₂Less than 10g/10 minute.

Another kind of polymkeric substance be density 900 to 930kg/m ³And melt flow index MI ₂Be 0.1 to 20g/10 minute multimodal ethylene polymkeric substance, described ethene polymers comprises:

Account for ethene polymers gross weight 30 to 70wt%, density is at least 950kg/m ³And melt flow index MI ₂Be at least the first polyethylene part of 10g/10 minute, and

Account for the second polyethylene part of 70 to 30wt% of multimodal ethylene total polymer weight, described the second polyethylene portions is divided the alpha's alkene that contains 3 to 12 carbon atoms that comprises ethylene unit and 0.1 to 20 % by mole, and melt flow index MI ₂Less than 10g/10 minute.

The loop reactor that uses among the present invention namely is the reactor of making therein above-mentioned the first or the second polyolefine part.

Although can make in more than two reactors, most preferably, polymkeric substance is the bimodal polymers of making in the reactor of two continuous serial connections.One or two reactor can have at least internal diameter of 700mm along at least 50% of its length.The first polymkeric substance of making in first reactor can be lower molecular weight (LMW) polymkeric substance, and the second polymer of making in second reactor can be high molecular (HMW) polymkeric substance.In one embodiment, 30-70wt% and more preferably the lower molecular weight of 40-60wt% (LMW) polymkeric substance in first reactor, make, and 70-30wt% and more preferably the high molecular of 60-40wt% (HMW) polymkeric substance in second reactor, make.The most preferred range of the ratio of HMW polymkeric substance and LMW polymkeric substance is that 45-55wt% compares 55-45wt%.

In another embodiment, the HMW polymkeric substance is made in first reactor, and the LMW polymkeric substance is made in second reactor, preferred same ratio as previously discussed.Following requirement is only applicable to this embodiment.In this case, the first (HMW) reactor preferably has greater than 100kg/m ³/ h, more preferably greater than 150kg/m ³/ h, and most preferably greater than 250kg/m ³The space-time yield of/h (being defined as the polymer production (kg/h) of per unit volume reactor).In this case further preferably, the ratio of the space-time yield in the space-time yield in first (HMW) reactor and second (LMW) reactor is greater than 1, more preferably greater than 1.2, most preferably greater than 1.5.This can become to be not more than 90% of second (LMW) reactor volume by the Volume design with first (HMW) reactor, and preferably at 30-70%, and more preferably from about 40-60% realizes.In these cases, preferably, the length of first reactor and diameter (L/D) more are selected between 500 to 3000, most preferably greater than 750 than greater than 350.Perhaps or and, the ratio of the L/D of the L/D of first reactor and second reactor also is preferably greater than 1.5, most preferably greater than 2.

In HMW-LMW embodiment of the present invention, when the volume difference of reactor is not more than 10%, preferably, maintain between 60 ℃ to 80 ℃ by the temperature with first reactor, preferably be not higher than 75 ℃, come activity between the balanced reaction device and cooling power separately.Further preferably, the ratio of the solids concn in the solids concn in first reactor and second reactor is maintained at less than 1.0, preferably between 0.6 to 0.8, because this also helps the active balance between two reactors is maintained the scope of wanting.Usually, the solids concn in last reactor is at least 35wt%, and most preferably between 45wt% to 60wt%, and the solids concn in the HMW reactor is between the 20wt% to 50wt%, more preferably between 25wt% to 35wt%.In these cases, preferably use the concentrated solid that is transferred to second reactor from first reactor of negative area and/or hydrocyclone, with thickened solid concentration.Most preferably will introduce in the upstream of hydrocyclone without the thinner fluid of comonomer, minimize so that be transferred to the comonomer of downstream reactor, thereby the density potential (density potential) in the LMW reactor is maximized.Solids concn is based on the weight of polymkeric substance in granular polymer slurry gross weight.

If the HMW polymkeric substance is to produce in the reactor of the upstream of LMW polymer reactor, then the ratio of the mean inside diameter of the mean inside diameter of preferred HMW reactor and LMW reactor is between 0.8 to 1.4, usually less than 1, preferably less than 1.2, most preferably less than 1.4.In this structure, preferably, at least 50% of LMW reactor overall length is 700mm at least, and the mean inside diameter of HMW reactor is less than 700 millimeters, preferably less than 600 millimeters.

If the LMW polymkeric substance is to produce in the reactor of the upstream of HMW polymer reactor, then the ratio of the mean inside diameter of the mean inside diameter of preferred HMW reactor and HMW reactor is between 0.6 to 1.4, usually between 0.8 to 1.2, most preferably between 0.9 to 1.1.Preferably, reactor has identical mean inside diameter, and most preferably, two reactors are constructed to identical size.

Generally with reference to the present invention, when the multiple reactor system comprises two loop reactors, preferably, Froude number at least one loop reactor is not more than 30, and the ratio of the Froude number in that reactor and Froude number in another loop reactor 0.1 to 10, preferred 0.2 to 5 scope.

In another embodiment of the present invention, the slurry that contains polymkeric substance is reclaimed from second reactor and is transferred in the flash tank, described flash tank operates under certain pressure P and temperature, so that the liquid component of at least 50 % by mole slurry is reclaimed from flash tank as steam.Preferably, aforesaid method so that at least 98 % by mole, more preferably 98.5 % by mole, most preferably 98.5 % by mole the steam that from flash tank, reclaims in the situation that not compression be condensed.Also preferably, at least 80 % by mole, preferred 90 % by mole, most preferably 95 % by mole the liquid component of slurry is reclaimed from flash tank as steam.

The pressure that uses in circulation or a plurality of circulation preferably is enough to keep reactive system " to be full of liquid ", does not namely substantially have gas phase.Normally used pressure is in the 1-100 bars absolute, preferably between 30 to 50 bars absolute.In vinyl polymerization, ethylene partial pressure in 0.1 to 5MPa scope, is preferably 0.2 to 2MPa usually, and 0.4 to 1.5MPa the most specifically.Selected temperature so that basically the polymkeric substance of all generations substantially to go up (i) be inviscid and the solid particulate form of non-caking and (ii) be insoluble in thinner.Polymerization temperature depends on selected hydrocarbon diluent and the polymkeric substance that produces.In vinyl polymerization, temperature is usually less than 130 ℃, usually between 50 to 125 ℃, preferably between 75 to 115 ℃.For example, in vinyl polymerization, in isobutane diluent, the pressure that uses in the circulation is preferably in the scope of 30-50 bars absolute, and ethylene partial pressure is preferably in the scope of 0.2-2MPa, and polymerization temperature is 75-115 ℃ scope.The space-time yield of the inventive method (polymer-through-out rate of per unit loop reactor volume) 0.1-0.4, be preferably 0.2-0.35 ton (ton)/hour/m ³Scope.When two or more circulation were arranged, in different circulation, reaction conditions may be identical or different.

Method of the present invention is applicable to the composition that preparation contains alkene (optimal ethylene) polymkeric substance, and described olefin polymer can comprise one or more olefin homos and/or one or more multipolymers.It is particularly suitable for the manufacturing of ethene polymers or propene polymer.Alpha-olefin(e) centent that ethylene copolymer comprises usually is variable, and it can reach 12% weight, is preferably 0.5 to 6% weight, for example about 1% weight.

Be generally used for alpha's monoolefine monomer in such reaction and be that one or more per molecules have at the most 8 carbon atoms and at the 1-alkene that does not have branch than 4 more approaching pair of key places.Typical example comprises ethene, propylene, butene-1, amylene-1, hexene-1 and octene-1, and mixture (for example ethene and butene-1 or ethene and hexene-1).Butene-1, amylene-1 and hexene-the 1st, particularly preferred comonomer for ethylene copolymerization.

Be generally used for thinner in such reaction and comprise that per molecule has 2 to 12, the hydrocarbon of preferred 3 to 8 carbon atoms, linear paraffinic hydrocarbons (for example propane, normal butane, normal hexane and normal heptane) or branched paraffin (for example Trimethylmethane, iso-pentane, octane-iso and 2 for example, or cycloalkanes (for example pentamethylene and hexanaphthene) or their mixture the 2-dimethylpropane).In the situation that vinyl polymerization, the formed polymkeric substance of (preferably at least 70%) is insoluble under the temperature of thinner making at least 50%, and thinner is inertia for catalyzer, promotor and the polymkeric substance (for example liquid aliphatic hydrocarbon, alicyclic hydrocarbon and aromatic hydrocarbons) that produces usually.Trimethylmethane is particularly preferred thinner for vinyl polymerization.

Operational condition also can be so that monomer (for example ethene, propylene) is used as thinner, just as in the so-called mass polymerization.Find, whether molecular weight and the thinner that can be independent of thinner are inertia or active, liquid state or postcritical, use slurry concentration limits (percent by volume).Propylene monomer is the particularly preferred thinner of propylene polymerization.

The method of molecular-weight adjusting is known in this area.When using Ziegler-Natta type catalyzer, metallocene-type catalyst and three teeth recently during (tridentate late) transition metal type catalyzer, preferably use hydrogen, higher hydrogen pressure causes producing lower molecular-weight average.When using chromium type catalyzer, preferably come the Molecular regulator amount with polymerization temperature.

In commercial plants, granular polymer separates with thinner in the not contaminated mode of thinner, to allow to utilize the purifying of bottom line (if any), with diluent recycle to polymeric area.The granular polymer that the inventive method is produced separates with thinner usually and can be undertaken by any known method in this area, for example the method can comprise: (i) use discontinuous vertical settling post, so that provide polymer beads to be settled down to a certain degree zone from thinner through the slurry flow of its opening, perhaps (ii) reclaims by the single or multiple continuous products that reclaim mouth, the position of reclaiming mouthful can be on loop reactor Anywhere, but the preferred downstream end of the horizontal component of contiguous circulation.Any continuous recovery mouth has 2-25, preferred 4-15, the particularly internal diameter of 5-10cm scope usually.The present invention can operate extensive polymerization reactor, and the diluent recovery aspect require low.React device so that the amount of the main thinner that reclaims minimizes with the operation of the high solid concentration in slurry major diameter from polymerization circulation.The polymer slurries that reclaims is used concentrating unit, preferred hydrocyclone is (single, or in the situation that a plurality of hydrocyclone, arranged side by side or serial connection), can further promote the recovery of thinner in the mode of Energy Efficient, because avoided the vaporization of the thinner of significant decompression and recovery.

Find, by mean particle size and/or the size-grade distribution of powder in the control reactor loop, can optimize the slurry concentration in the reactor loop.The main determining factor of the mean particle size of powder is the residence time in reactor.The size-grade distribution of powder can be subjected to many factor affecting, comprise the soundness of the size-grade distribution that is added to the catalyzer in the reactor, initial and average catalyst activity, support of the catalyst and under reaction conditions powder to the susceptibility of fragment.The slurry that solid separating device (for example hydrocyclone) can be used to reclaim from reactor loop is with mean particle size and the size-grade distribution of powder in the further subcontrol reactor.Design and the operational condition of the position in the recovery site of concentrating unit and concentrating unit system (preferably at least one hydrocyclone recirculation circulation), also so that reactor in granularity and size-grade distribution controlled.Mean particle size is preferably between 100 to 1500 microns, most preferably between 250 to 1000 microns.

When the last reactor of multiple reactor system was loop reactor, before being introduced into main flasher, (and the preferably being concentrated) polymer slurries that reclaims was depressurized, and randomly is heated.Fluid preferably is heated after decompression.

The thinner that reclaims in main flasher and any monomer vapor usually are condensed (preferably not again compression) and are used further in the polymerization process.The pressure of main flasher is preferably controlled, so that before any again compression, with the heat-eliminating medium that can easily obtain (for example, water coolant) comes basically all flash vapors of condensation, usually the such pressure in described main flasher will be the 4-25 bars absolute, 10-20 bars absolute for example, preferred 15-17 bars absolute.The solid that reclaims from main flasher preferably is transferred in the secondary flash vessel, to remove residual volatile matter.Perhaps, slurry can be transferred to have than above-mentioned main flasher more in the flasher of low pressure, thereby need to again compress the thinner that reclaims with condensation.The preferred high pressure flash vessel of using.

Method of the present invention can be used to produce proportion 890 to 930kg/m ³(low density), 930 is to 940kg/m ³(intermediate density) or 940 is to 970kg/m ³Resin in (high-density) scope.

Method of the present invention is relevant with all olefin polymerization catalyst systems, particularly is selected from the Ziegler type catalyzer catalyzer of titanium, zirconium or vanadium (particularly from), thermal activation silicon-dioxide or the chromium oxide catalyst of inorganics load and system's (metallocenes is the cyclopentadienyl derivative of transition metal (particularly titanium or zirconium)) of metallocene-type catalyst.

The non-limitative example of Ziegler type catalyzer is, by magnesium compound is mixed the compound of the transition metal, magnesium and the halogen that comprise the IIIB family, IV B family, V B family or the VI B family that are selected from the periodic table of elements that obtain with transistion metal compound and halogenated compound.Halogen optionally forms the integral part of magnesium compound or forms the integral part of transistion metal compound.

Metallocene-type catalyst can be by luxuriant oxygen alkane (alumoxane) or by for example patent application EP-500, the metallocenes of the ionizer activation of describing among the 944-A1 (Mitsui Toatsu Chemicals).

Ziegler type catalyzer is most preferred.Wherein, special example comprises transition metal, magnesium and at least a halogen of at least a IIIB of being selected from family, IV B family, VB family or VI B family.The catalyzer that use comprises following element can obtain good effect:

The transition metal of 10 to 30% weight, preferred 15 to 20% weight,

The halogen of 20 to 60% weight, preferred 30 to 50% weight,

0.5 to the magnesium of 20% weight, be generally 1 to 10% weight,

0.1 to the aluminium of 10% weight, be generally 0.5 to 5% weight,

All the other common origin come from elementary composition for the preparation of their product, for example carbon, hydrogen and oxygen.Transition metal and halogen are preferably titanium and chlorine.

Polyreaction, the particularly polyreaction of Ziegler catalysis are normally in the situation that exist promotor to carry out.May use any promotor known in the art, the compound that particularly comprises at least one aluminium-carbon chemical bond, for example randomly organo-aluminium compound of halo (its can comprise oxygen or from the element of the I family of the periodic table of elements) and aikyiaiurnirsoxan beta (aluminoxanes).Special example may be following organo-aluminium compound: trialkylaluminium, for example triethyl aluminum; Three alkenyl aluminium, for example three pseudoallyl aluminium; Aluminium single methanol salt and aluminium two alkoxide, for example diethyl aluminum ethylate; Monohalogenated and dihalogenated aluminum alkyls, for example diethylaluminum chloride; Aluminum alkyls one hydride and aluminum alkyls dihydride, for example dibutyl alanate; With the organo-aluminium compound that contains lithium, LiAl (C for example ₂H ₅) ₄Organo-aluminium compound, particularly those are not halogenated, and are fit closely.Triethyl aluminum and triisobutyl aluminium are particularly advantageous.

Preferably include the chromium oxide catalyst of the load with the carrier that contains titanium dioxide based on the catalyzer of chromium, the described carrier that contains titanium dioxide for example is compound silicon-dioxide and titania support.Particularly preferred catalyzer based on chromium can comprise 0.5 to 5wt% the chromium that accounts for chromium-containing catalyst weight, the chromium of preferred approximately 1wt%, for example chromium of 0.9wt%.Carrier comprises the titanium of at least 2wt% that accounts for chromium-containing catalyst weight, preferred approximately 2 to 3wt% titanium, the more preferably from about titanium of 2.3wt%.Catalyzer based on chromium can have 200 to 700m ²The specific surface area of/g is preferably 400 to 550m ²/ g, and greater than the volume porosity of 2cc/g, be preferably 2 to 3cc/g.

By silicon dioxide carried chrome catalysts usually will be in air, under the activation temperature that raises, stand initial activation step.Activation temperature is preferably 500 to 850 ℃ scope, more preferably 600 to 750 ℃.

Reactor assembly can comprise one or more serial connections or the loop reactor that connects side by side, is preferably serial connection.

If series reactors, then first reactor of reactor string is except thinner and monomer, also be supplied catalyzer and promotor, and each follow-up reactor is supplied at least monomer (particularly ethene) and derives from the slurry at front reactor of reactor string, and this mixture comprises catalyzer, promotor and at the mixture of the polymkeric substance that produces of reactor string in front reactor.Randomly, may to second reactor and/or, if suitable, at least one reactor is thereafter supplied original catalyzer and/or promotor.But preferred is introduced into catalyzer and promotor in first reactor.

If at least two reactors serial connection produces in have the polymkeric substance of high-melt index and have that the polymkeric substance of lowest melt index can be in the reactor string two the adjacent or non-conterminous reactors.Hydrogen (i) is maintained at low (or zero) concentration in the reactor of making high molecular weight components, the hydrogen percentage ratio that for example comprises 0-0.1 volume %, (ii) in the reactor of making low molecular weight compositions, be maintained at very high concentration, for example the hydrogen percentage ratio of 0.5-2.4 volume %.Reactor can be operated comparably, to produce substantially the same polymer melt index in continuous reactor.

But, relevant with the production of fluoropolymer resin for the special sensitivity that in major diameter reaction device, operates (with relevant cross section component gradient, thermal gradient or particle gradient), wherein known higher molecular weight or low-molecular-weight fluoropolymer resin cause increasing the misgivings to dirt, particularly when producing molecular weight less than 50k dalton or greater than the daltonian polymkeric substance of 150k.Confirmed especially is that when polymer solids concentration was low in reactor loop, these misgivings were increased the weight of.But, when in major diameter reaction device, producing molecular weight less than 50k dalton or greater than 200k dalton's (or melt index is less than 0.1 with greater than 50) polymkeric substance, surprisingly find, when solid loadings is increased to greater than 20 volume %, during particularly greater than 30 volume %, dirt has reduced.

Embodiment

As previously mentioned, an advantage of the present invention is, the cross-sectional slurry concentration distribution is at high reactor diameter, even during high solids loadings, can be maintained in the acceptable operational limits.Actual cross-sectional slurry concentration distribution is not measurable directly, but can measure other parameters as the sign of slurry homogeneity.

Embodiment 1

In following examples, ethene is by polymerization in the reactor of two serial connections.The volume of first reactor is 96m ³And along the internal diameter that has 730mm above its length of 98%.Solids content is 27-28 volume %.The volume solids content is defined as (slurry volume of volume PE productivity/discharge reactor), wherein: the density of volume PE productivity=(the ethene quality of the ethene quality-outflow reactor of adding)/PE]

The liquid volume of the volume of the slurry of discharge reactor=discharge+volume PE productivity

The volume of the liquid of discharge reactor=[the PE quality of the quality summation of adding-generation]/fluid density.

PE density is measured dry and degassed powder.

Fluid density is based on any suitable model (model) (utilizing component, temperature and pressure) and calculates.

The circulation pump power requirement

The power requirement of the recycle pump in the loop reactor not only is subjected to the pressure influence of fluid, and affected by slurry concentration gradient.It is responsive especially to concentration gradient, because it is positioned at the knee of loop reactor, here most probable has fluid isolation (segregation), and this causes the change of the density of the slurry that is pumped.When have seldom dirt and good circulation time, observe power demand (power demand) temporal evolution and relatively constant.Fig. 1 shows the polyreaction for embodiment 1, within one hour time, and the power of pump and the chart of current requirements (with relative value but not absolute value draw).The variation that herein demonstrates is greater than for the desired variation of neat solvent, but is little for the slurry that contains polymkeric substance, demonstrate generation very little or the slurry isolation do not occur.

Temperature of reactor

The temperature of different loci also is subjected to the impact of slurry concentration gradient in the reactor.Absolute difference between the temperature that different loci is measured in reactor may be owing to the difference of the scale of thermopair, therefore in order to determine " really " difference of temperature, has measured the variation during the temperature transition.In inhomogenous slurry, the trend of this temperature transition can change.Fig. 2 shows such transformation of the polyreaction of embodiment 1.Fig. 2 demonstrates, and in embodiment 1, temperature transition trend is constant in whole reactor, demonstrates good homogeneity.

The heat transfer coefficient of reactor wall

The material impact of reactor dirt is to change the heat transfer coefficient through reactor wall.Heat transfer coefficient can be measured by long time (a plurality of months), does not form the dirt material in this time without any reducing namely to be presented at.Fig. 3 shows the heat transfer coefficient of embodiment 1 in 250 days, can find out from it, the reducing for a long time of coefficient (long-term reduction) do not occur.

Claims (20)

1. method, it is included at least one continuous tubulose loop reactor of multiple reactor system, in thinner, in the situation that there is polymerizing catalyst, with the olefinic monomer polymerization, randomly with olefinic monomer with the olefin comonomer polymerization, the slurry that comprises solid particulate olefin polymer and thinner with generation, at least 50% mean inside diameter of wherein said continuous tubulose loop reactor overall length is 700mm at least, high molecular (HMW) polymkeric substance is made in first reactor, lower molecular weight (LMW) polymkeric substance is made in second reactor, and the space-time yield in first (HMW) reactor (being defined as the polymer production take kg/h as unit of per unit volume reactor) is greater than 100kg/m ³/ h, the ratio of the space-time yield in the space-time yield in first (HMW) reactor and second (LMW) reactor is greater than 1.

2. the process of claim 1 wherein that the volume of first (HMW) reactor is not more than 90% of second (LMW) reactor volume.

3. claim 1 or 2 method, wherein the ratio of the mean inside diameter of the mean inside diameter of first (HMW) reactor and second (LMW) reactor is between 0.8 to 1.4.

4. the method for claim 3, wherein at least 50% of the total length of second (LMW) reactor is 700mm at least, and the mean inside diameter of first (HMW) reactor is less than 700 millimeters.

5. claim 1 or 2 method, wherein the L/D ratio of first reactor (L/D) and the ratio of the L/D of second reactor are greater than 1.5.

6. claim 1 or 2 method, wherein the solids concn in described continuous tubulose loop reactor is at least 20 volume %.

7. the method for claim 6, wherein the solids concn in described continuous tubulose loop reactor is at least 25 volume %.

8. the method for claim 6, wherein the solids concn in described continuous tubulose loop reactor is at least 30 volume %.

9. claim 1 or 2 method, at least 50% mean inside diameter of wherein said continuous tubulose loop reactor overall length is 750mm at least.

10. claim 1 or 2 method, wherein at least one reactor in described multiple reactor system, Froude number is maintained at below 30 or 30.

11. the method for claim 10, wherein at least one reactor in described multiple reactor system, Froude number is maintained between 1 to 20.

12. the method for claim 10, wherein at least one reactor in described multiple reactor system, Froude number is maintained between 2 to 15.

13. the method for claim 1 or 2, wherein the total pressure drop in the circulation of reactor is less than 1.3 bar, and polymer-through-out rate is greater than per hour 25 tonnes.

14. the method for claim 13, wherein the total pressure drop in the circulation of reactor is less than 1 bar, and polymer-through-out rate is greater than per hour 45 tonnes.

15. the method for claim 1 or 2, at least 30wt% of the whole polymkeric substance that wherein produce in described multiple reactor system makes in described continuous tubulose loop reactor.

16. the method for claim 1 or 2, wherein the density span of polymeric powder particles is less than 0.005, described density span be defined as discharging reactor, granularity greater than the mean density of the polymer beads of D90 and granularity less than between the mean density of the material of D10 with g/cm ³Be the absolute value of the density difference of unit, wherein D10 and D90 are respectively such diameters: the diameter of the particle that 10% and 90% weight is collected is less than this diameter.

17. the method for claim 16, wherein the density span of polymeric powder particles is less than 0.003.

18. the method for claim 16, wherein the density span of polymeric powder particles is less than 0.0026.

19. the method for claim 16, wherein the density span of polymeric powder particles is less than 0.0023.

20. the method for claim 1 or 2, wherein:

The density of multimodal ethylene polymkeric substance 900 to 930kg/m ³Between and melt flow index MI ₂Be 0.1 to 20g/10 minute, described ethene polymers comprises:

Account for ethene polymers gross weight 30 to 70wt%, density is less than 950kg/m ³And melt flow index MI ₂Be at least the first polyethylene part of 10g/10 minute, and

Account for the second polyethylene part of described multimodal ethylene total polymer weight 70 to 30wt%, described the second polyethylene portions is divided the alpha's olefin unit that contains 3 to 12 carbon atoms that comprises ethylene unit and 0.1 to 20 % by mole, and melt flow index MI ₂Less than 10g/10 minute.

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