CN100343287C

CN100343287C - Multi-step solid state devolatilization of syndiotactic vinyl aromatic polymers

Info

Publication number: CN100343287C
Application number: CNB2004800030656A
Authority: CN
Inventors: J·施伦比尔格; H·勒德; H·赫尔曼
Original assignee: Idemitsu Kosan Co Ltd
Current assignee: Idemitsu Kosan Co Ltd
Priority date: 2003-01-28
Filing date: 2004-01-05
Publication date: 2007-10-17
Anticipated expiration: 2024-01-05
Also published as: WO2004069882A1; CN1745110A; TW200422312A; KR20050105183A

Abstract

A multi-step polymer devolatilization process comprising a) heating a slurry comprising solid particles of syndiotactic vinyl aromatic polymer, residual vinyl aromatic monomer, and optionally residual processing solvent and active catalyst residue in a first contacting device in the presence of steam and isolating a polymer product; b) contacting the polymer obtained in step a) with an inert fluid under devolatilization conditions and separating the fluid and the polymer, and c) melting, extruding and pelletizing the resulting polymer product.

Description

The multiple stage solid state devolatilization of syndiotactic vinyl aromatic polymers

Cross-reference statement:

It is No.60/443 that the application requires application number, the right of priority of 313 U.S. provisional application, and its applying date is on January 28th, 2003.

The background technology of invention:

Method of the present invention relates to the method for preparing syndiotactic vinyl aromatic polymers.For example in the preparation of syndiotactic polystyrene (SPS), from the SPS polymkeric substance, remove residual monomer, process solvent and other volatile components with the step of devolatilization at vinylaromatic polymer usually.The complicacy of this method is that residual vinyl aromatic monomers and other monomer may autopolymerization when heating form the fact of atactic vinyl aromatic and other polymkeric substance, for example, random isotactic polystyrene, it is a undesirable pollutent in SPS.Atactic vinyl aromatic has reduced SPS polymer properties (for example heat-drawn wire) and has reduced the crystallization rate of SPS homopolymer and copolymer resin.

In order to prevent darkening of SPS polymkeric substance, before devolatilization process, extract active catalyst residues usually by the deliming step.The deliming step requires the deliming agent of use-case example hydrochloric acid, potassium hydroxide and analogue thereof to handle polymkeric substance.Alternatively, under the situation of low catalyst levels, can simply active catalyst residues be carried out inactivation before devolatilization, catalyst residue is in final resin thus.Usually, by polymkeric substance and active nucleophilic reagent, the protonic solvent of preference such as methyl alcohol, close mixing realize deactivation.

The method of several devolatilizations known in the state of the art comprises wherein at first the polymer melt melt devolatilization of devolatilization under liquid state then; Wherein with solid polymer heating and under the second-order transition temperature of polymkeric substance and the temperature between the fusing point solid state devolatilization of devolatilization.

The JP03056504 of Yamamoto discloses a kind of melt devolatilization process, and the SPS powder that wherein will contain volatile matter is sent in the twin screw extruder, carries out fusion and devolatilization therein.Although volatile residues has reduced, in order to prevent that owing to the variable color that exists active catalyst residues to cause catalyst deactivation and deliming step are necessary.

The JP03064303 of Yamamoto discloses a kind of two-step approach solid state devolatilization process, the SPS powder that wherein at first will contain volatile matter is sent in the moisture eliminator, be heated the temperature between SPS second-order transition temperature and the fusing point therein, in as the vacuum exhaust twin screw extruder of describing among the above-mentioned JP03056504, come devolatilization then by the melt devolatilization step.But this method is very consuming time, needs 9 or just can finish in 10 hours, and catalyst deactivation and deliming step also are necessary.

From SPS polymkeric substance deliming and the several method that makes the active catalyst residues inactivation by known to the people.People's such as Kuramoto U.S. Patent No. 5,321,122 discloses a kind of method by also coming the purified styrene polymkeric substance with the alcohol washing with alkali metal alcohol solution deliming.People's such as Teshima U.S. Patent No. 5,426,176 discloses a kind of being greater than or equal under the temperature of glass transition temperature of polymer, by using deliming agent, for example carries out the method that deliming comes the purified styrene polymkeric substance with HCl, KOH.The U.S. Patent No. 5,449,746 of Teshima discloses a kind of swelling agent of using, for example ethylbenzene, and deactivator, and for example methyl alcohol or ethanol handle the method for purified styrene polymkeric substance.The U.S. Patent No. 5,612,452 of Teshima and Yamasaki discloses and has a kind ofly contained 15 to 10 by use, and the poor solvent of 000ppm water is handled polymkeric substance and simultaneously crystalline styrene carried out the method for deliming and inactivation.But these methods all are extra postprocessing working procedures, and it has improved preparation technology's the complicacy and the cost of SPS polymkeric substance.

In U.S. Patent No. 5,877, disclose in 271 and a kind of syndiotactic polymer has been carried out the method that devolatilization forms the rapid heating syndiotactic polymer of low color body simultaneously.In U.S. Patent No. 6,031, in 070, for the remainder catalyst in the final polymkeric substance of while inactivation and the residual monomer that reduces in the final polymkeric substance have used steam.Exemplified and wherein used two moisture eliminators, wherein first uses steam, and second is used nitrogen, carries out the multi-stage method that melt extrudes of final product subsequently.

Although by the making progress property of prior art that above-mentioned technology forms, the economic and method syndiotactic vinyl aromatic polymers of the low residual monomer content of preparation as one man remains desired, when particularly its end-use is relevant with Food Contact.The example removes directly contact and uses, and for example beyond baking tray and food storing and/or the reheat container, also comprises food product pack and food processing plant.For these application, residual monomer content is lower than 500ppm, preferably is lower than 100ppm, even is very gratifying more preferably less than the polymkeric substance of 50ppm.Therefore, still there is the volatile matter that preparation is had reduction, particularly the needs of the syndiotactic vinyl aromatic polymers devolatilization process of the polymkeric substance of the residual monomer content of Jiang Diing.

Summary of the invention:

The present invention is the rapid polymer devolatilization process of a kind of multistep, comprises:

A) in the presence of steam, heating comprises solid particulate syndiotactic vinyl aromatic polymers, residual vinyl aromatic monomers and the optional remaining process solvent and the incoming mixture of active catalyst residues in first contact arrangement, and the isolating polymer product;

B) under the devolatilization condition, the polymkeric substance that step a) is obtained contacts with inert fluid, and separation of the fluid and polymkeric substance and

C) fusion, extrude the polymer product that obtains with granulation.

This improved devolatilization process has been removed volatile matter from the syndiotactic vinyl aromatic polymers solid, residual vinyl aromatic monomers particularly, and make the active catalyst residues inactivation simultaneously, thus obtain being suitable for the product that Food Contact is used.In addition, do not need independent deliming and/or deactivation step.Astoundingly, use improved devolatilization process of the present invention to obtain the polymkeric substance that residual monomer is low with other volatile constituent content, random isotactic polystyrene content is low, variable color reduces and improved whiteness.

Detailed Description Of The Invention:

The description of all relevant periodic table of elements herein all is meant CRC Press, Inc., 2001 editions disclosed periodic table of elements.In addition, descriptions of all relevant families or group also are meant family or the group that uses the period of element table definition that the IUPAC system is numbered family.For the purpose of patent practice, introduce in full indication herein any patent, patent application or open in content as a reference, particularly relevant the analysis or the open and ordinary skill knowledge of the prior art of synthetic technology.

Term " comprises " and its version is not got rid of the existence of other composition, step and operation, and it can be with disclosed herein identical or different.In order to dispel one's misgivings, unless opposite explanation is arranged, can comprise any additives, batching or compound by using term " to comprise " desired all compositions herein, and no matter it is a polymeric or non-polymeric.On the contrary, term " basically by ... form " from described scope thereafter, got rid of other component, step or operation, unless other component, step or operation can not cause substantial effect to working of an invention.Term " by ... form " got rid of all other components, step or the operation not narrating especially or list.Term " or ", except as otherwise noted,, also refer to its arbitrary combination except referring to listed single cell.

Term " polymer " used herein " comprise homopolymer, it is the polymkeric substance that is made by the single reaction compound, and multipolymer, it is the polymkeric substance that is made by at least two kinds of reactive monomers.Term " crystalline " refers to that polymkeric substance presents the X-ray diffraction spectrogram at 25 ℃, and has first-order transition or crystallization fluxing point (Tm).This term can exchange with term " hemicrystalline " and use.Term " syndiotaxy " is meant that polymkeric substance has greater than 90% syndyotactic, be preferably greater than 95% syndyotactic by ¹³The stereoregular structure of the racemize triad that the C nuclear magnetic resonance spectrum records.

Syndiotactic vinyl aromatic polymers is a vi-ny l aromatic monomers, and promptly chemical structure contains the monomeric homopolymer and the multipolymer of unsaturated structure division and aromatic structure part simultaneously.Preferred vi-ny l aromatic monomers has following molecular formula:

H ₂C＝CR-Ar (I)

Wherein R is that H or the alkyl with 1 to 4 carbon atom and Ar are the aryl that contains 6 to 10 carbon atoms, comprises the cyclosubstituted aryl of alkyl or halogen.The example of this class vi-ny l aromatic monomers has vinylbenzene, alpha-methyl styrene, o-methyl styrene, a vinyl toluene, p-methylstyrene, Vinyl toluene, to t-butyl styrene, vinyl naphthalene, Vinylstyrene, chloro-styrene, bromstyrol and analogue thereof.Syndiotactic polystyrene is at present preferred syndiotactic vinyl aromatic polymers.The typical polymerization processes and the coordination catalyst systems of preparation syndiotactic vinyl aromatic polymers are well known to those skilled in the art, and at United States Patent (USP) 4,680, and 353,5,066,741,5,206,197 and 5,294,685 and existing description the in other.

In the polymerization process of vi-ny l aromatic monomers, polyreaction does not have complete reaction usually, and what often obtain is syndiotactic vinyl aromatic polymers and volatile matter, for example the mixture of residual monomer and process solvent.This mixture contains based on mixture total weight amount about 2 usually to about 99%, and preferred about 30 to about 95%, and more preferably from about 40 to about 95%, most preferably from about the 70 solid-state non-volatile high-molecular weight polymers to about 90% (weight).The bulk density of charging is usually less than 400kg/m ³, preferably be lower than 350kg/m ³Average particle size particle size (dp ₅₀) be usually less than 500 μ m, preferably be lower than 400 μ m.Adopt subsequently postorder (finishing) technology for example devolatilization can from mixture, reclaim polymkeric substance to produce resin, this resin can be used for forming injection-molded item, film, fiber etc.Method of the present invention is a kind of improved method that is used for syndiotactic vinyl aromatic polymers/volatile matter mixture (hereinafter referred to as " charging " mixture) is carried out devolatilization.

Usually, below 100 ℃, typically under 10 to 90 ℃ temperature, from polymerization reactor or polymer recovery system, discharge incoming mixture.Subsequently under the temperature of the second-order transition temperature (about 100 ℃ usually) of the syndiotactic vinyl aromatic polymers of devolatilization and fusing point (usually at 200 to 320 ℃), steam and choose any one kind of them or multiple catalyst deactivation agent in the presence of, this mixture is carried out devolatilization.To reach the necessary time of required level of volatiles removal in order reducing, before contacting or simultaneously, this mixture heating up can be arrived at least 110 ℃, more preferably at least 125 ℃ with steam.In one embodiment of the invention, with steam itself as heating medium to reach above-mentioned temperature limitation requirement.

Can adopt any means heating incoming mixture in the method for the invention.The example of this heater means includes but not limited to indirect dryer, and wherein charging contacts with the metallic surface of being heated by suitable heat-transfer fluid, for example collar plate shape, cydariform, low speed and high speed paddle formula, rotary and screw rod transmission moisture eliminator; The kinetic energy well heater comprises the batch-mixed/homogenize machine by the plough type/mixing drier of high speed blade enhancement, pneumatic hammer mill or use high speed agitator; Utilize the convection drying device of hot gas flow heating, for example dodge moisture eliminator; All types of fluidized bed dryers, conveyor-type moisture eliminator, pan dryer and direct heating type rotatory drier; Traditional moisture eliminator/heating unit of promoting with the combination of boosting technology such as radiated infrared, microwave heating or similar techniques or these technology.Suitable miscellaneous equipment comprises adiabatic, purger, mass flow hopper and storage warehouse.

The fs of devolatilization process carries out in the presence of steam, this steam makes contained active catalyst residues inactivation in the incoming mixture, thereby make it to further polyreaction inactivation, this step also helps the removal (purging) of residual volatile component simultaneously.Preferably, described steam is producing in the technology separately, and is heated to (superheated vapour) of the above temperature of boiling point of water under devolatilization pressure.Alternatively, liquid water can be injected directly in the devolatilization apparatus, perhaps mix, gasify by heating whole mixture thus with incoming mixture.Charging mixes inlet, sweep gas (steam) inlet and liquid infusion port should be arranged such that in devolatilization apparatus that maximize the duration of contact between incoming mixture and steam.It is desirable to steam and be distributed to fast in the polymeric matrix and the reaction of reactive residual catalyst component, make catalyst deactivation thus, avoided the variable color or the degraded of polymkeric substance simultaneously to prolong its exposure at elevated temperatures.

Highly it is desirable to make steam in the first devolatilization device, to contact with incoming mixture, wherein said steam is at 130 to 210 ℃, under preferred 150 to the 210 ℃ temperature, with the mass ratio 0.5 to 10 of steam and volatile matter, preferred 1 to 5 amount adds with respect to the charging contrastream injection.

Except that steam, other catalyst deactivation agent also can be used for step a).Typically, except that steam, can also be with the vaporous form of any active nucleophilic compound that can make residual activity catalyst component inactivation.These compounds comprise the organic and mineral compound of a large amount of polarity, for example by the compound shown in the following general formula: C _iH _jO _kS _lN _mX _n(II), wherein X is fluorine, chlorine, bromine or iodine, and i is 0 to 6 integer, and j is 0 to 14 integer, and k is 0 to 3 integer, and l and m are that 0 to 2 integer and n are 0 to 6 integer, satisfy all suitable valence mumbers like this.

Usually, if use, the molecular weight that is characterized as of suitable catalyst deactivation agent is lower than about 100 dalton, has limited solubleness in prepared polymkeric substance, and compatible with steam or water vapour.This has not only been avoided the follow-up step that removes, and has avoided steam reaction used in itself and inactivation and the devolatilization process and the degraded that causes.Utilization again for the monomer that promotes to reclaim in the devolatilization steps and other volatile constituent, and prevent the variable color of potential polymkeric substance, preferred any cocatalyst deactivator under the used condition of devolatilization process with vinyl monomer and process solvent also anergy.The used typical cocatalyst deactivator of the present invention comprises carbonic acid gas, carbon monoxide, hydrogen sulfide, sulfurous gas, ammonia, polar organic compound for example alcohol, aldehyde, ketone and its analogue and their combination.

The amount that satisfies the expection necessary steam of deactivation or its and other catalyst deactivation agent composition depends on the residual volume of all active catalyst component in the incoming mixture, and still, employing is significantly excessive fully usually in order to ensure inactivation.The mass velocity of used steam/catalyst deactivation gaseous mixture is generally 0.1 to 80% of feed mixture flow rate.High expectations be that steam or vapour mixture are to pass conversion unit with respect to the mode of incoming mixture adverse current.150 to 270 ℃, preferred 150 to 210 ℃ vapor temperature is that expectation is adopted.

Except that the mixture of steam or steam and other catalyst deactivation compound, pair active catalyst residues can also be arranged or separate out volatile constituent inoperative and also can not be aggregated other rare gas element that thing absorbs significantly.Typical rare gas element comprises nitrogen, rare gas such as argon and helium, alkane such as methane and ethane, hydrogen and its mixture.These components play thinner, can assist the amount of volatile matter being removed and reduced remaining volatile matter in the desciccate from devolatilization apparatus.In order to reach the expection level of devolatilization best, the mol ratio of the mixture of rare gas element and steam or steam and other catalyst deactivation compound is no more than 99/1 usually.

The fs of improvement devolatilization process of the present invention can implement under the very wide working pressure of devolatilization apparatus, as long as steam can keep the steam attitude under the temperature and pressure that devolatilization process adopts.Devolatilization process can be carried out at normal atmosphere or near under the atmospheric pressure, or carries out under the pressure of rising or reduction in the suitable devolatilization apparatus of design.Adopt vacuum condition under negative pressure, from devolatilization apparatus, to remove and separate out volatile matter and excessive steam or other deactivator.High expectations be that first devolatilization steps adopts superheated vapour, particularly 130 to 210 ℃ superheated vapour, or approach to implement under the atmospheric pressure.

Result as the heating incoming mixture comprises that the volatile constituent of residual vinyl aromatic monomers is released from polymkeric substance, gasify, and be transferred out equipment with flowing out steam.The residence time of polymkeric substance in devolatilization apparatus answers sufficiently long to the residual volume of vi-ny l aromatic monomers in the polymkeric substance of the devolatilization initial value by incoming mixture, be generally 5 to 60% of the polymer weight that accounts for devolatilization, be reduced to and be lower than 3%, preferably be lower than 1%.For the required residence time in devolatilization apparatus of the volatile matter level that reaches above-mentioned reduction is depended on overall flow rate in the initial volatile content of incoming mixture, temperature, catalyst deactivation gas and the rare gas element in the devolatilization apparatus, absolute pressure in the devolatilization apparatus and the physical features of incoming mixture.Usually, devolatilization carries out under certain condition, is 24 hours or still less so that reach the required residence time of above-mentioned residual vinyl aromatic monomer content, be generally 12 hours or still less, preferred 4 hours or still less, more preferably 1 hour or still less and most preferably 30 minutes or still less.

The expectation be, with incoming mixture be heated rapidly to about 110 ℃ to the temperature between the syndiotactic vinyl aromatic polymers fusing point.Preferably, mixture heating up is arrived than low about 20 ℃ to the 100 ℃ temperature of complete drying melting point polymer.Rapid heating is usually can be with at least 10 ℃/minutes, typically at least 10-1000 ℃/minute, preferably at least 20 ℃/minutes, more preferably at least 30 ℃/minutes and most preferably at least 40 ℃/minutes mean rate improve in the equipment of incoming mixture temperature and carry out.By heating with faster rate, residual monomer is easier to volatilization rather than polymerization, has so just reduced the generation of atactic vinyl aromatic.

After step a), in second devolatilization apparatus (those disclosed in the step a) as described above), contact for the second time with adverse current devolatilization reagent by making polymer product, thereby it is carried out further devolatilization.Suitable devolatilization reagent comprises steam, aforementioned auxiliary devolatilization reagent and rare gas element and its mixture that is used for step a).The devolatilization reagent of used special expectation is the mixture of steam or steam and auxiliary devolatilization reagent in the step b).The preferred embodiment of the suitable devolatilization apparatus of using in the step b) is direct and indirect-heat drier.The expectation equipment that is used for step b) is that the high temperature rotatory drier that the contrastream injection mouth of devolatilization reagent and gas are removed mouthful is housed.The temperature of the devolatilization reagent that is adopted in second contact procedure is identical or higher with the temperature of steam that adopts in first devolatilization steps or vapour mixture.The temperature of the devolatilization reagent of expecting in the step b) is 150 to 270 ℃, preferred 170 to 230 ℃.

In order to reach the variable color of reduction in the polymkeric substance that makes in technology according to the present invention, feed vapors is before step a) is finished at least, and it is important that preferred steps a) is all finished former the contact with air or oxygen with step b).Therefore, feed vapors and prepared polymkeric substance and the catalyst deactivation gas or the rare gas element of above-mentioned definition are kept in touch.In addition, before being injected into devolatilization apparatus, should filter the pollutent or the particle that may cause that to remove chromoplastid forms to steam or vapour mixture.

The final step of devolatilizing polymers is fusion, extrudes and granulation step, being to use degassing extruder or making the forcing machine of operating under the pressure that reduces of expectation.The used this example that melt extrudes equipment of step c) comprises the single screw rod and the twin screw extruder of deflated or vacuum equipped, and it is equipped with water-bath or simple water cooler and knife mill or similar granulation facility.If desired, can also filter fused devolatilization product.

Utilize these devices also can be by for example the polymer formation blend or the alloy of antioxidant, processing aid, anti-impact modifier, fire retardant, filler such as glass fibre and mineral substance and other polymeric material and generation prepare the formulation product with additive.In efficient production technology, by using tablets press, for example water-bath condenser and knife mill, resulting devolatilization extrudate can be made into the bead of uniform shapes.High expectations be that the product that is extruded reaches enough degree of crystallinity before cooling and granulation, so that the formation na non agglomerating opaque solid globules of not luming.

Expectation be, to the process between the step b), also incoming mixture will be remained under the intensification in step a) except step b) is to the process between the step c).Usually step a) to the product temperature between the step b) is 120 to 200 ℃, and step b) is to being 140 to 200 ℃ between the step c).Preferably after step a) and step b), carry out fusion and extrusion step continuously.This melt extrudes step and is being elevated to melting point polymer or preferred is carrying out under than the high at least 10 ℃ elevated temperature of polymer crystallization fusing point.The highest extrusion temperature of polymer melt desirably is lower than on the polymer crystallization fusing point 50 ℃.For syndiotactic polystyrene, what the last temperature that melt extrudes the stage was expected is 240 ℃ to 320 ℃.The preferred vacuum condition that adopts is with the volatile constituent in the further reduction melt in fusion and extrusion.Usually, in extrusion, adopt 1000 to 5000 handkerchiefs, the pressure of preferred 1000 to 1500 handkerchiefs.

For the opaque bead of crystallization, can detect the color reduction degree of syndiotactic vinyl aromatic polymers according to the ASTM E313 standard of measuring yellowness index or YIE with devolatilization process preparation of the present invention.Usually, the YIE value of the polymkeric substance that makes according to the inventive method is less than 10.Alternatively, also can adopt ASTM D1925 standard, it uses light transmission techniques to come the comparison equal thickness to advance the yellowness index of transparent extruded film.

With reference to the sample of known composition, the content of residual vinyl aromatic monomers can with suitable solvent for example orthodichlorobenzene measure with headspace gas chromatography.The content of nonstereospecific polymer can be measured in order to Soxhlet (Soxhlet) extraction method of methyl ethyl ketone, methyl ethyl ketone is the solvent of atactic vinyl aromatic, also is the non-solvent of crystallization syndiotactic vinyl aromatic homopolymers and multipolymer simultaneously.

Usually, the weight-average molecular weight (Mw) of the syndiotactic vinyl aromatic polymers that makes according to the inventive method is at least 15,000, preferably is at least 50,000 and most preferably be 150,000 to 500,000.Polymer crystallization fusing point Tm desirably is higher than 240 ℃, preferably is higher than 245 ℃.In addition, polymkeric substance before devolatilization desirably bulk density be 175kg/m at least ³, preferred 200kg/m at least ³Arrive up to 400kg/m ³, preferably be lower than 350kg/m ³With average particle size particle size dp ₅₀Be at least 75 μ m, preferably be at least 100 μ m, up to 450 μ m, preferably up to 400 μ m.

With the polymer phase ratio that adopts conventional catalyst deactivation technology to make, the prepared syndiotactic vinyl aromatic polymers of the improved devolatilization process of the present invention has the residual vinyl aromatic monomers of reduction and the colourity of other volatile constituent level and reduction, preferred vinyl aromatic monomer level is lower than 500ppm, preferably is lower than 400ppm.In addition, can be condensed, utilize again, thereby reduce the potential emission amount in environment as the steam of catalyst deactivation agent and devolatilization reagent.

The present invention is further illustrated for the following examples.These embodiment are used for also should not being considered as being intended to limit the scope of the invention.Unless otherwise noted, all consumptions are all represented with weight part or weight percentage.

Embodiment 1:

The syndiotaxy styrene homopolymers raw material that will contain 20% volatile matter component, nonstereospecific polymer and active catalyst residues less than 1% from polymerization reactor system under the inert conditions of ingress of air not, send in the after-treatment system of forming by two rotatory driers that the heating of adverse current vapor injection mouth is housed with the speed of 1800kg/hr, forcing machine is arranged thereafter.First moisture eliminator is a SJS 48-30 type moisture eliminator, and second moisture eliminator is a CRJS 60-23 type moisture eliminator, and the two is all made by Hosokawa Bepex company.Described forcing machine is a Berstorff ZE 130A type twin screw extruder, and its L/D=25 is equipped with a vacuum evacuating system (1500 handkerchief).First moisture eliminator moves under 210 ℃ of the discharge zone jacket temperatures, speed of rotation 100rpm 185 ℃ of feed zone jacket temperature.To approach atmospheric steam filtration to remove pollutent, be preheating to 210 ℃, and with the speed of 800kg/hr, with 2.22: 1 mass ratio of steam/volatile matter to send in first moisture eliminator with the direction of stream of solids adverse current.The drop temperature of powdered product is 196 ℃.

With the feeding rate of 310kg/hr, the similar steam that is preheating to 210 ℃ is fed in second moisture eliminator with the mass ratio of steam/polymkeric substance 0.251.Second moisture eliminator moves under 210 ℃ even cover temperature.The powder that leaves moisture eliminator has 143 ℃ temperature, and is directly delivered to the opening for feed of forcing machine.The barrel set points of forcing machine is 150 to 275 ℃, and spiro rod rate is 150rpm.Make the extrudate of devolatilization form band shape, in water-bath,, and be cut into bead its cooling.

Residual styrene content in the resulting polymers bead that is recorded by headspace gas chromatography is 350ppm.The content of random isotactic polystyrene is 0.52% in the polymkeric substance.The remaining organic decomposition thing of polyalcohol catalyst is less than 12ppb, the limit that gas chromatography-mass spectrum (GC-MS) is measured.

Embodiment 2:

Syndiotaxy vinylbenzene/p-methylstyrene the multipolymer that comprises 92.3% styrene units and 7.7% p-methylstyrene that will contain 20% volatile matter, the nonstereospecific polymer less than 1% and active metallocene catalyst resistates is directly sent in the identical aftertreatment technology that embodiment 1 adopted with the speed of 1350kg/hr from polymerization reactor system.The jacket temperature in the first dryer feed district remains on 120 ℃, and the discharge zone jacket temperature remains on 130 ℃, and speed of rotation is 100rpm.With approaching the speed of the adverse current steam of normal atmosphere and 175 ℃, send in first moisture eliminator with the mass ratio of steam/volatile matter 2.222 with 600kg/hr.The powder of devolatilization leaves first moisture eliminator at 129 ℃, is admitted to second moisture eliminator, therein with flow rate 300kg/hr, with steam/powder quality than 0.278 identical vapour source Continuous Contact.Second moisture eliminator moves under 175 ℃ even cover temperature.The hot powder that leaves second moisture eliminator has 146 ℃ temperature, and is sent to the opening for feed of forcing machine, is extruded and granulation in the water-cooled tablets press.The barrel set points of forcing machine is 150 to 260 ℃.Final monomer content in the bead is 377ppm.The content of random isotactic polystyrene is 1.1% in the polymkeric substance.The remaining organic decomposition thing of polyalcohol catalyst is less than 12ppb, the determination limit of gas chromatography-mass spectrum (GC-MS).

Claims

1. rapid polymer devolatilization process of successive multistep, wherein the residual monomer total amount in the syndiotactic vinyl aromatic polymers of devolatilization is less than 500ppm, and based on the gross weight of devolatilization syndiotactic vinyl aromatic polymers, this method comprises:

A) normal atmosphere or near under the normal atmosphere with steam: 1: 5 superheated vapour usefulness 150-270 ℃ temperature and the incoming mixture adverse current of volatile matter mass ratio comprises solid particulate syndiotactic vinyl aromatic polymers, residual vinyl aromatic monomers and optional remaining process solvent and active catalyst residues incoming mixture to 110 ℃ to the temperature between the fusing point of this syndiotactic vinyl aromatic polymers with at least 10 ℃/minutes V-bar heating in first contact arrangement, wherein the residence time is 24 hours or still less, and the isolating polymer product;

B) temperature that step a) is obtained be 120-200 ℃ polymkeric substance at normal atmosphere or near contacting with the superheated vapour of 170-230 ℃ of temperature under the normal atmosphere, wherein the residence time is 24 hours or still less, and separation of the fluid and polymkeric substance and

C) fusion, extrude the polymer product with the granulation gained under than the high at least 10 ℃ temperature of polymer crystallization fusing point, prerequisite is that this incoming mixture does not contact with air or oxygen before step a) and step b) finish.