WO1998022518A1

WO1998022518A1 - Continuous process for producing thermoplastic molding materials

Info

Publication number: WO1998022518A1
Application number: PCT/EP1997/006118
Authority: WO
Inventors: Wolfgang Fischer; Hermann Gausepohl
Original assignee: Basf Aktiengesellschaft
Priority date: 1996-11-21
Filing date: 1997-11-18
Publication date: 1998-05-28
Also published as: DE19648245A1

Abstract

The invention relates to a continuous process for producing polybutadiene rubber impact-resistant modified styrol polymers, wherein the styrol is polymerized radically in two areas in a high-boiling solvant in the presence of a rubber dissolved in an originally low-boiling solvant which has been prepared immediately prior to styrol polymerization by anionic means in a plug flow, and wherein both solvants are removed from and fed once again into the first of theses reaction zones by means of evaporative cooling.

Description

Continuous process for the production of thermoplastic molding compositions Description

The invention relates to a continuously feasible process for the preparation of impact-modified styrene polymers which contain a particulate polybutadiene rubber which has been contracted by grafting with styrene or a styrene-butadiene block copolymer as a disperse phase in a polystyrene matrix, by polymerizing styrene in the presence of the immediately Chews manufactured before the styrene polymerization. Impact-resistant polystyrene is usually free radical

Polymerization of styrene in bulk in the presence of a rubber, which is dissolved in styrene and obtained in an independent process. In addition, a solvent such as ethylbenzene is usually used. The polymerization is carried out technically in several reactors arranged in series, a so-called cascade. Such methods are compiled, for example, by Echte, Handbuch der Techniscnen Polymerchemie, Weinheim 1993; special arrangements are e.g. in U.S. Patents 2,727,884 or 3,903,202.

It is also proposed to produce polystyrene in tubular reactors, the heat of polymerization having to be listed on the wall. For this purpose, so-called static mixers are built into the pipe section, which require the radial diameter of the polymer (Nguyen Khac Tien et al. Chem. Engg. Techno. 13, 214-220 (1990).

Rubbers such as polybutadiene are usually produced in solution or by the bulk suspension process. For this purpose, the summary in Encyclopedia of Polymer Science and Technology Vol. 2, N.Y. Referred in 1985.

In the case of anionic polymerization, such as is used for the production of so-called block rubbers (styrene-butadiene block copolymers), a solvent is in any case necessary (EP-A-510 410; EP-A-554 142; US 5 286 457 ).

The majority of the processes in which a separately manufactured and solid rubber is used (polybutadiene, styrene-butadiene block rubber or another rubber that can be used for the impact modification of polystyrene) consists in the additional work steps (shredding, loosening , Filtration), which are required to prepare the rubber before it can be used in the polymerization.

It has therefore been proposed several times to produce the required rubber immediately before the styrene polymerization and to use it in already dissolved form without further process steps.

For this purpose - in the case of rubbers containing butadiene - it was first necessary to ensure that the rubber is monomer-free, since the

Presence of butadiene which would interfere with styrene polymerization (by crosslinking). Therefore, after the end of the polymerization, either the remaining butadiene had to be separated off in a separate step or - in the case of anionic polymerization - the butadiene feed had to be interrupted after a certain time and polymerization was complete before styrene was added and polymerization was continued. Both ways rule out a fully continuous process.

In addition, in most cases, the solvent used had to be removed and replaced with another, unless ethylbenzene, the usual solvent for styrene polymerization, was to be used from the outset (and what would be associated with the disadvantages described below).

British Patent 1,013,205 describes a process in which the rubber is first polymerized in cyclohexane, then styrene is added and the cyclohexane - together with the residual monomers - is distilled off before the polybutadiene in styrene solution obtained is used to produce impact-resistant polystyrene can be used. This process cannot be put into practice; it could practically only be carried out in batches and therefore poorly integrated into a continuous process. In addition, an additional solvent was required, which had to be removed in a separate process step

The disadvantages of this procedure are clearly described in European patent publication 059 231. A process is then proposed in which styrene and butadiene are first processed anionically in a Ruhr kettle, ie with back mixing, to form an SB block copolymer. The reaction is carried out in such a way that a butadiene-containing reaction mixture is finally obtained, from which excess butadiene is removed, the living polymers are treated with a quenching agent and the rubber is first precipitated. Then styrene had to be added and radically polymerized. This procedure differs in principle not from the procedure for prefabricated polybutadiene rubber, ie the rubber is first precipitated before further processing, or surplus butadiene will be removed in a separate - naturally discontinuous - process step in order to avoid disturbances in the styrene polymerization, as mentioned.

European patent application 334 715 therefore recommends that polybutadiene - anionic - be first prepared in ethylbenzene in a stirred tank. After termination, it should be diluted with preheated styrene and polymerized to a solids content of 30%. The polymerization is finally completed in other reactors.

This process, too, disadvantageously cannot be carried out continuously, since a process which is operated continuously in a stirred tank generally does not lead to complete conversion. The rubber solution thus obtained would always contain more monomeric butadiene.

A further disadvantage of all of the aforementioned processes is that, because of the high solution viscosity of the polybutadiene, only dilute solutions can be handled, so that a large amount of solvent is circulated, which in turn requires a high amount of energy (removal of distillable constituents, so-called "degassing" of the polymer; Cleaning the solvent) means and you accept a slow reaction rate. If ethylbenzene is used as a solvent for the production of the rubber, as proposed in EP-Al-334 715, an amount is required which is so high that in the subsequent (radical) styrene polymerization, the effect of ethylbenzene as a chain transfer agent, that is to say the regulating effect, can be felt: The molecular weights are too low, ie poor polymer properties achieved. All of these methods have therefore not been introduced into technology.

The object of the invention was therefore to provide an economical process which can be carried out continuously and continuously, in which a rubber based on butadiene is prepared immediately before the styrene polymerization and is not obtained in solid form, which avoids the disadvantages of the known processes which have been presented.

Generally speaking, the process is characterized in that the required rubber is produced in a non-revering reaction space by continuous anionic polymerization until conversion is complete. The rubber may be a polybutadiene rubber, an SB (styrene / butadiene) rubber or be an SB block rubber. Thereafter, the polymerization of the styrene is carried out continuously in the usual way, by radical polymerization in the presence of the rubber solution.

An immediate subject of the invention is a process of the type mentioned at the outset, which is carried out in at least three reaction zones or stages, polymerizing butadiene and, if desired, styrene anionically until at least one reaction zone to complete conversion into a rubber, essentially without backmixing, in at least one first reaction zone,

the block of polybutadiene or styrene-butadiene obtained - immediately or after adding a demolition or

Coupling agent is fed to a second reaction zone in which, with the addition of a quantity of styrene which is sufficient to achieve phase inversion, radical polymerization is carried out until phase inversion and the heat of polymerization is at least partially removed by evaporative cooling and

In a third reaction zone with as much styrene as is required to form the target product, that is to say an impact-modified styrene polymer, the polymerization ends radically.

When styrene or butadiene is mentioned above, the usual respective technical equivalents are also meant. For styrene are e.g. 2-, 3- or 4-methylstyrene, ter. -Butylstyrene, ethylstyrene or α-methylstyrene or other substitution products of styrene with a similar polymerization behavior ("vinyl aromatic compounds"). In addition to butadiene, other dienes or combinations of dienes and vinyiaromatic compounds are suitable as monomers for the production of the rubber. Examples of dienes are butadiene, isoprene, dimethylbutadiene, 1, 3-pentadiene or 1, 3-hexadiene.

The process according to the invention is expediently carried out in solution such that a solvent is used for the first reaction zone which has a boiling point - at atmospheric pressure - below 130, preferably below 120 ° C. and, if desired, a solvent for the second reaction zone , which has a boiling point above 120 or 130 ° C at atmospheric pressure. If no special solvent is used in the second zone, the monomeric styrene (K ι ₀ ι _h p ~ 145 ° C) serves as the sole solvent. When using evaporative cooling in accordance with the invention, the temperature of reaction zone 2 which is established corresponds to the boiling point of the monomer or the boiling point of the mixture of monomer and solvent. The process can of course also be carried out at a pressure other than atmospheric, for example reduced or superatmospheric pressure. A pressure range from 0.5 to 5 bar is suitable, for example. The relative boiling behavior of the solvents, which is important here, is generally not particularly affected by this.

Suitable solvents for use in the production of the rubber are aliphatic or cycloaliphatic hydrocarbons with 4 to about 8 carbon atoms or mixtures thereof with a boiling temperature (KP ₁₀ ι _h p) of below 130 ° C. Examples include pentane, hexane, heptane, cyclohexane or methylcyclohexane. It is essential that these solvents meet the usual requirements for use in anionic polymerization, in particular are free of proton-active substances and oxygen. They are expediently distilled before use and dried over aluminum oxide or molecular sieve.

In reaction zones 2 and 3, the aromatic solvents customary for radical styrene polymerization are used, for example alkylbenzenes corresponding boiling point such as xylenes (K ιoι _3hP = = 140 ° C) or ethylbenzene (K ι ₀ ι _3h p: 136 ° C). The unreacted styrene can also take over the task of evaporative cooling according to the invention and possibly even replace the entire solvent entirely, depending on the intended conversion and the viscosity which is still under control.

In this process, the first reaction zone, which according to the invention is essentially not supposed to work backmixing, is expediently formed at least partially and in any case at the end of this zone as a tubular reactor. The tube reactor can be subdivided into a plurality of tube sections arranged one behind the other, with all or part of the tube section having mixing elements in the form of fixed internals (so-called static mixers). Part of the pipe section can be designed as an empty pipe without a heat exchanger. Another pipe section can have a heat exchanger. It goes without saying that an arrangement in which a stirred kettle is initially provided, which is used to produce a prepolymer which is then polymerized to the end with further monomer in a tubular reactor, can also be used as the embodiment according to the invention. It is crucial that the butadiene monomer used to form the rubber is practically completely converted before the reaction mixture enters the second reaction zone, where styrene is added for the matrix polymer. This is achieved in a manner known per se by means of a reaction space which does not allow jerk mixing, ie by means of the pipe section arranged at least at the end of the first zone.

If desired, the discharge from this zone is mixed with styrene in the second reaction zone after termination of the live chain ends with a customary quenching agent, ie a protic compound; the addition of a solvent for polystyrene, the boiling point of which is above 130 ° C., is, as said, not absolutely necessary for the use of the invention.

The second reaction zone, in which the free-radical polymerization is to proceed until phase inversion, can be designed as a back-mixing unit (unit with Ruhr boiler - behavior) and, according to the invention, has an assigned evaporator, i.e. trained as a reflux condenser

Heat exchanger and a downstream heat exchanger, αer does not generate a return.

According to the invention, the two solvents and, in each case, unreacted styrene in the second reaction zone are still distilled off together, but are separately condensed and used again at the relevant point in the process sequence.

The weight of added styrene is l.a. at least 3 times the weight of the rubber or block copolymer. The mixture is radicalized in a manner known per se, optionally with the addition of radical initiators, to the extent that the phase inversion is exceeded. The turnover here is l.a. set to a value between 5 and 60, preferably 7.5 and 55% by weight. The solids content is e.g. 10 to 60, preferably 15 to 50%. According to the invention, the heat of polymerization is essentially removed by evaporative cooling, so that a polymerization temperature is established which corresponds approximately to the boiling point of the higher-boiling solvent, e.g. between 130 and 180 ° C, depending on the pressure.

The reaction mixture obtained in the second reaction zone is then polymerized in accordance with the invention in at least one further reactor (third reaction zone) until the desired end conversion. Depending on the solvent content, the third reaction zone strives for a styrene conversion of 70 to 90%. As a reac In addition to stirred tanks, gates are also suitable here, as are the tower reactors known from styrene polymerization, which can be regarded as reactors with more or less pronounced plug flow. Fully filled (ie operated without a gas space) cycle reactors or tubular reactors are also suitable. The polymerization temperature here is between 140 and 200 ° C, for example.

The monomer which has not yet reacted at the end of the third reaction zone and the accompanying solvent are separated off from the polymer in a customary manner by so-called degassing and returned to the second reaction zone.

The (in the stirred tank: average) residence time in the individual reaction zones is, for example, 0.1 to 3, advantageously 0.2 to 1.5 hours in the first, 0.3 to 3, advantageously 0.5 to 2 hours in the second and 0.5 to 5, advantageously 1 to 3 hours in the third reaction zone.

This method can advantageously be operated continuously throughout. By choosing a non-aromatic solvent in rubber production, undesired transfer reactions are avoided and this solvent (in which the impact-resistant polystyrene would be essentially insoluble at a higher solids content) can be separated from the reaction mixture easily and economically. The reaction speed of the radical polymerization taking place is only slightly influenced and there is not an uneconomical amount of solvent being circulated.

The procedure in detail (see figure):

The first reaction zone, in which the anionic polymerization takes place, consists at least in part of one or more non-backmixing reactors (A and B, as well as possibly further tube elements, not shown), in which a plug flow is thus maintained. Suitable reactors are tubes or tube bundles, which are preferably equipped with static mixers. Pipes or shell-and-tube heat exchangers with commercially available static mixers (e.g. SMX or SMXL-

Mixers from Sulzer and so-called Kenics mixers or SMR reactors). These mixers are described, for example, in Chem. Eng. Commun., Vol. 36 pp. 251-267 or Chem. Eng. Technol. 13 (1990), pp. 214-220. It is also possible to use a continuously operated tank reactor (CSTR) instead of a first tubular reactor (A - see figure), but then a tubular reactor must be used in any case Follow plug flow to ensure that the butadiene used is practically quantitatively converted. In the Abbil ^¬ dung arrangement shown with two tube reactors (A and B) can be extended by splitting on more than two pipe sections and also enables the continuous production of block copolymers by prior to or into each reactor further monomers and optionally further initiator be dosed. The reaction in the first reaction zone can take place adiabatically, partially adiabatically or isothermally.

The second reaction zone essentially consists of a Ruhr boiler Rl with a fractional evaporator (heat exchanger) Kll and a downstream condenser (heat exchanger) K12.

In this second reaction zone, at least one styrene monomer is polymerized in the presence of the rubber from the first reaction stage and preferably an aromatic solvent until phase inversion. This reaction zone thus serves to set the desired particle morphology of the chewing nut (cf. Echte, I.e.).

The aforementioned heat exchangers K1 and K12 are used for the fractionation and condensation of the vapors. The heat exchanger Kll should be dimensioned and operated in such a way that the unreacted styrene and the aromatic (high-boiling) solvent are separated off in Kll and immediately returned to the second reaction zone (the reactor Rl - see Fig.), While the low-boiling point Solvent remains in vapor form and is fed to the heat exchanger K12 for condensation; the heat exchanger Kll is thus a component which is said to have a certain fractionation effect, similar to a column, which in the usual way, e.g. is achieved by internals, full body or simply corresponding length.

During the K12 period, the low-boiling solvent is then separated off and collected in a tank which, ia after appropriate reprocessing (cleaning and drying), is returned to the first reaction zone. Small amounts of non-aromatic, low-boiling solvent in the discharge from the second reaction zone can be tolerated. The discharge from this reaction zone is further polymerized in a further, third reaction zone (Ruhr kettle R2) before the polymer solution is finally freed of (“degassed”) low-molecular constituents in a suitable surface evaporator (degasser E). The advantage of the process according to the invention is that a single polymerization cascade with only monomeric feedstocks can be produced continuously and in solution with modified impact materials.

Another advantage is the possibility to convert existing plants, in which the required rubber has previously had to be dissolved in styrene, with relatively little effort, i.e. upstream of a continuous rubber production and thus significantly improve its economy.

The production of impact-resistant polystyrene is described in more detail below with the aid of the illustration.

In the first reaction zone (pipe sections A; B) as

Rubber e.g. a styrene-butadiene block copolymer can be produced. For this purpose, dried and stabilizer-free styrene, dried solvent (e.g. cyclohexane) and a suitable initiator solution (e.g. sec-butyllithium) are continuously added to reactor A, e.g. a double-jacket tube reactor equipped with SMXL mixers (manufacturer: Sulzer AG; W terthur; Switzerland), metered, which practically completes the conversion, i.e. at the end of which there is no monomeric styrene menr. Butadiene and, if necessary, initiator solution are added between reactor A and reactor B. Also in reactor B, e.g. also a double-walled tube reactor equipped with SMXL mixers is polymerized practically until conversion is complete. The living chain ends are broken off with a protective demolition agent (e.g. l-propanol). This is also expedient in a short pipe section, which is however omitted from the illustration.

By including additional pipe sections to which styrene is added and polymerized and, if necessary, coupling, three-block or star block copolymers can be obtained in the usual way. The number of reactors (pipe sections) depends on the desired composition of the rubber. According to the feed sequence, linear block copolymers, for example of the type (AB) _n , ABA, BAB, can also be obtained by coupling with suitable coupling agents, the corresponding star block copolymers. If a pure butadiene rubber is to be produced, a single reactor (for example pipe section B) is sufficient, which has all the necessary features (static mixer; heat exchanger). All monomer feeds are expediently cooled to a temperature below room temperature, for example 0 to 20 ° C. The rubber solution is drawn off continuously at the end of the first reaction zone and if necessary without further ado, that is to say at the temperature prevailing at the end of reaction zone 1, into a Ruhr kettle with a sieve cooler (R1) attached. The concentration of the rubber solution, ie the amount of solvent to be selected initially, can be varied within wide limits. However, the amount of solvent is limited downwards by the viscosity of the solution and upwards by economic considerations. Solids contents of 5 to 60% by weight are expedient, but preferably 20 to 45% by weight.

Styrene and optionally aromatic solvent (for example ethylbenzene) are added to the Ruhr kettle R1 and polymerized at a temperature of 100 to 220 ° C., preferably 120 to 180 ° C. If the temperature to be maintained is below the normal boiling point of the solvent (Kpιoι _3h p), it may be necessary to work under reduced pressure to achieve sufficient cooling. Otherwise, atmospheric or superatmospheric pressure of a suitable pressure range (boiling point of styrene or solvent) is suitable.

The amount of styrene added should be at least 3-fold

Amount by weight based on the rubber. The conversion m Rl is selected so that the phase inversion takes place in this reaction zone, which means that dispersed rubber particles are formed in a polystyrene matrix. The desired size of the rubber particles is set in a known manner by a suitable choice of the shear conditions (cf.

The solvent separated from the reaction zone 1 in the second heat exchanger of the evaporator becomes more careful

Cleaning and drying (drying agents such as aluminum oxide or molecular sieve) are fed back to reaction zone 1.

The reaction mixture from the Ruhrkessel Rl is continuously drawn off and polymerized in a further reactor R2, a Ruhrkessel up to the desired conversion (about 65 to 90%), the desired thermoplastic molding material being obtained in the form of a (concentrated) melt-like solution. If higher viscosity is to be expected, it may make sense to use a hydraulically filled circuit reactor, a tower reactor or a tubular reactor with static fittings instead of the Ruhr boiler: Success does not depend on whether the reactor R2 works with jerk mixing, ensures plug flow or has a mixture characteristic in between. The reaction enthalpy (residual heat) can of course also be removed by evaporative cooling in a Ruhr boiler, provided that sufficient solvents are available; Furthermore the technical solutions that are introduced in the technology of styrene polymerization are suitable (eg tower reactors with built-in coolers that reach between the arms of the Ruhr; cooling jacket).

The polymer solution finally obtained is degassed at 190 to 320 ° C. in a conventional device (extruder or a conventional apparatus, as is usually used for degassing polymers). The vapors drawn off essentially consist of unreacted styrene and the aromatic solvent. The vapors are appropriately condensed and can be l.a. be fed directly to the reactor R1.

According to the invention, “rubber” is understood to mean any anionically producible polydiene, including statistical, linear or star block copolymers with a sharp or smeared transition of the type (AB) _n , ABA, BAB or (AB) _m X, (BA) _m X, ( ABA) _m X, (BA-) _m X, where X is the residue of a multifunctional coupling agent and A is a block of vinyl aromatic monomer and B is a block of a diene, n is an integer from 1 to 6 and m is an integer from 2 to 10 means.

Both Block A and Block B can contain statistical butadiene and styrene. Preferred block copolymers are those of styrene, α-methylstyrene, butadiene and isoprene. The glass transition temperatures of the diene-containing segments of the rubber produced should be below -20 ° C, in particular below -40 ° C. The statistical structure is achieved by copolymerization of styrene and butadiene with the addition of small amounts of Lewis bases such as dimethyl ether, tetrahydrofuran, diethylene glycol dimethyl ether, alkali metal salts of primary, secondary and tertiary alcohols or by tertiary amines such as Pyridm, tributylamm. These connections are m amounts of 0.1 to 5 vol .-% used. Alcoholates such as potassium tetrahydrolmaloate are required in an amount of 3 to 20 mol%, based on the initiator used.

The block lengths are characterized by a molecular weight of the blocks in the range from 1,000 to 500,000 and preferably in the range from 20,000 to 300,000. The block length can be set for each individual block by choosing the ratio of initiator and monomer and, if necessary, by so-called initiator splitting. This means the division of the initiator along the reaction zone 1. The total styrene content in the rubber is 0 to 85% by weight, preferably 0 to 60% by weight and particularly preferably 0 to 45%. The 1,2-vmyl content should be less than 30 wt .-%, based on the weight fraction of the diene block.

Multifunctional compounds such as aldehydes, ketones, esters, anhydrides or polyfunctional epoxides can be used to couple the rubbers.

Mono- or multifunctional alkali metal alkyls or aryls can be used to initiate anionic polymerization. For reasons of value for money and manageability, primarily organolithium compounds are used. Ethyllithium, propyllithium, isopropyllithium, n- or sec-butyllithium, t-butyllithium, phenyllithium, hexyldiphenyllithium, hexamethylenedilithium and butadienyllithium or isoprenyldilithium may be mentioned as examples. The dosage depends on the desired molecular weight, but is generally in the range from 0.002 to 5 mol%, based on the monomers.

Proton-active substances or Lewis acids such as water, alcohols, aliphatic or aromatic carboxylic acids and weak mineral acids, e.g. Carbonic acid or boric acid.

In addition to styrene, other vinylaromatic compounds are suitable as monomers for the production of the impact-resistant thermoplastic molding compositions, as stated at the beginning. Instead of styrene, α-methylstyrene, tert-butylstyrene, vinyltoluene, p-methylstyrene and mixtures of the compounds mentioned are particularly preferably used.

Lubricants, stabilizers or mold release agents can be added as an aid in free-radical polymerization. Examples

Preliminary note

When manufacturing the rubber, care must be taken that the reaction temperature and residence time are chosen so that the conversion is practically complete. The residual butadiene content at the end of the pipe section should not be more than 1000 ppm, since otherwise crosslinking reactions are to be expected in the subsequent styrene polymerization, as mentioned at the beginning. raw materials

The following are provided for the production of the rubber:

freshly distilled, anhydrous styrene; distilled and dried over alumina cyclohexane; butadiene dried over molecular sieve; sec. -Butyllithium, 1.2% in n-hexane / cyclohexane in a volume ratio of 1: 9.

The monomer required for the production of the polystyrene portion was not specially cleaned.

A mixture of 10% by weight of methanol and 90% by weight of ethylbenzene was used to terminate the butadiene polymerization (removal of the living chain ends).

Tests: Notched impact strength according to DIN 53453 on notched standards. Yield stress according to DIN 53 455 on test specimens according to ISO 3167.

The polymerization plant (see Fig.)

Reactor A, which, however, was not used in Example 1 below, consists of a 1 m long heatable tube of nominal size 50 (DN 50) with commercially available static mixers (SMX mixers, FabriKat Sulzer), which therefore has a content of approximately 1. Has 7 liters and can be fed to the monomer (St), solvent LM1 and initiator (In). Reactor B consists of a similar 3 m long tube. Butadiene (Bu) can be supplied either at the entrance of B or both at the entrance of A and B. Styrene (St) can be fed to reactor A as needed to produce a styrene-butadiene block copolymer. It is understood that in the event that e.g. an S-B-S three-block polymer is to be produced, the reactor B must also be supplied with styrene in addition to butadiene.

Reaction chamber R1 is a 30 liter Ruhr kettle equipped with an anchor stirrer with an attached reflux cooler and a downstream cooler, as shown in the figure. The reaction mixture can be discharged from the boiler R1 by means of a gear pump P1 and conveyed into the boiler R2. The boiler R1 contains the rubber coming from A and B, the solvent LM2, the vapors produced during the degassing (vapor line Br), the required amount of monomer (St) and optionally additives such as, for example Lubricant (Z) metered in, but can only be added in R2.

The boiler R2, like Rl, is equipped with an anchor stirrer and 5 has a volume of 50 1. It can be operated either with evaporative cooling (not shown in the figure) or with jacket cooling. Downstream is a gear pump P2, from which the reaction mixture can be discharged in the usual way and fed to a degassing device E. A 10 tube bundle heat exchanger is used for this purpose, which sits on an evacuable pot. A further gear pump P3 is provided for the product discharge, with a downstream nozzle plate and a granulating device.

15 Example 1

In this experiment, pure polybutadiene is used as the rubber. Reactor A is not required for this and is bypassed.

20th

35 ml of initiator solution, 1 kg of butadiene and 8 kg of cyclohexane are fed to the tube reactor B, which is heated to 65 ° C., and polymerized. After the chain termination (30 ml / h terminating agent), the residual butadiene content is 470 ppm.

25

The rubber solution obtained from A, the condensed vapors (7 kg / h consisting of 87.5% styrene and 12.5% ethylbenzene in addition to small amounts of cyclohexane and hexane) and 9.5 kg fresh styrene are conveyed in Rl. The stirrer speed

30 carries 70 rpm. The reaction temperature is 145 ° C, the average residence time 65 min. A solids content of 35% is reached. The reaction mixture is conveyed to R2, in which it is reacted at 154 ° C. and an average residence time of 120 min up to a solids content of 60%.

35

The reaction mixture is degassed and the product is granulated. The notched impact strength is 6.5 kj / m ² , the yield stress is 35 MPa.

Example 2

40

0.23 kg of styrene and 8 kg of cyclohexane were introduced into A every hour. B was charged with monomer and initiator as described in Example 1., so that a styrene-butadiene block copolymer was formed. The reaction temperature in A and B was 45 65 ° C. After chain termination, the residual butadiene content is 7 6118

15

240 ppm. The impact strength is 7.5 kJ / m ² , the yield stress is 31 MPa.

Example 3

A mixture of 7.4 kg of cyclohexane, 350 g of styrene and 31.2 ml of initiator solution is added to reactor A, which is at a temperature of 60 ° C. 955 g of butadiene and 14 ml of initiator solution are added to reactor B, which is heated to 65 ° C. The living chains are broken off after the reactor B with 30 ml / h of stopping agent. The rubber solution has a residual butadiene content of 420 ppm. The notched impact strength is 8.5 kJ / m ² , the yield stress is 36 MPa.

Claims

claims

1. Process for the continuous production of impact-modified styrene polymers containing a te lchenform, by grafting ιr.ιt styrene contractl cn made Polybutad enkautscnuK or a styrene-butadene block copolymers as a disperse phase in a polystyrene matrix, the polymerization of styrene present of the rubber produced immediately before the styrene polymerization, dadurcr. Kennze chnet that the process is carried out a train in at least three reaction zones, where

polymerized at least one first reaction zone butadiene and, if desired, styrene, essentially without an anionic mixture, to give a complete conversion to a rubber,

the polybutadiene or styrene-butadiene block rubber obtained is fed to a second reaction zone immediately or after the addition of a terminating or coupling agent, with the addition of a quantity of styrene which is sufficient to achieve phase inversion to be polymerized radically until phase inversion and the polymerisation - Warm on at least partially by sieving and a third reaction zone with as much styrene as is required to form the impact-modified styrene polymer, which leads to radicalization of the polymerization.

2. The method according to claim 1, characterized gekennzeicnne in that the first reaction zone e solvent with a boiling point (at atmospheric pressure) of below 130 ° C is used.

3. The method according to claim 1, characterized geκennzeιchnet that n solvent in the first reaction zone with a boiling point (ßi atmospheric pressure) below 130 ° C and in the second and / or third reaction zone e aromatic solvent with a boiling point (be atmospheric Pressure) of over 130 ° C is used.

4. The method according to claim 1, characterized in that the first reaction zone is divided into pipe sections, wherein at least one pipe section has mixing elements in the form of fixed internals, at least one (possibly further) pipe section is designed as an empty pipe without a heat exchanger and at least one (possibly another) pipe section is provided which has a heat exchanger.

5. The method according to claim 1, characterized in that the heat of polymerization liberated in the second reaction zone is substantially removed by evaporative cooling.

6. The method according to claim 2, characterized in that the second reaction zone for condensing the vapors are assigned at least two successive heat exchangers (coolers) which are dimensioned, arranged and temperature-controlled so that

unreacted styrene in the first heat exchanger and possibly the high-boiling added before the second reaction zone

Solvent condensed and returned to the second or third reaction zone and

The low-boiling solvent added before the first reaction zone is condensed in the second cooler and, if necessary after cleaning and drying, is returned to the first reaction zone.

7. The method according to claim 1, characterized in that a circulation reactor with static mixers or a Ruhr kettle is provided as the second reaction zone.