CZ236499A3 - Process for preparing polymers from vinyl aromatic compounds by dispersion polymerization - Google Patents

Abstract

A process for preparing vinylaromatic compounds polymers the dispersion comprises performing the present polymerization dispersant and catalyst obtainable from A) of the transition metal complex of subgroups II to VIII, B) of the reagent forming a cation and C) if desired, aluminum compounds.

Description

Process for preparing polymers from vinylaromatic compounds by dispersion polymerization

Technical field

The invention relates to a process for preparing polymers of vinyl aromatic compounds in dispersion in the presence of metallocene catalyst systems. The polymers thus obtainable can be used to make fibers, films and moldings.

BACKGROUND OF THE INVENTION

The polymerization of styrene in the presence of metallocene catalyst systems results in polymers of high stereoregularity and is described in detail in, for example, EP-A 0 210 615. Due to its high crystallization, syndiotactic polystyrene has a very high melting point of about 270 ° C, high tensile strength and stiffness. , dimensional stability, low dielectric constant and high chemical stability. The mechanical properties profile is maintained even above the glass transition temperature.

In metallocene-catalyzed styrene polymerization, crystallization of the resulting syndiotactic polystyrene often occurs at a conversion value of only about 10 ··. This leads first to the formation of bearings on the walls and then to an extreme viscosity during the polymerization, which makes processing and heat dissipation in the reaction more difficult, especially on an industrial scale.

A number of techniques have been tried to solve this problem using special reactors or extruders.

Pat. EP-A-0 535 582 discloses a process for the preparation of syndiotactic polystyrene in a stirred bed of solids which is capable of reducing but not preventing deposits on the walls. The reactor had to be equipped with a special stirrer to create a homogeneous fluidized bed. Temperature control is accomplished by partial evaporation of styrene by depressurization using a comprehensive vacuum control system.

Pat. EP-A-0 584 646 and EP-A 0 389 939 disclose the preparation of syndiotactic polystyrene in self-cleaning twin-screw extruders or blenders without dead spaces. In both processes, due to the sudden increase in frictional forces at higher conversion values and engine power required to continue the operation, polymerization is carried out not to complete conversion, but only to a value where the monomer-saturated polymer powder does not agglomerate during subsequent process steps.

In the case of anionic initiation, the dispersion polymerization technique is known. It is used to prepare small polystyrene particles, as described, for example, in Journal of Polymer Science, Part A, Polymer Chemistry, Volume 34 (1996), pages 2633-2649. The choice of dispersant for stabilizing the dispersion is essential.

DE-A 43 30 969 describes a process for preparing polystyrene mixtures by polymerizing styrene in an organic liquid in the presence of a styrene-butadiene block copolymer and a metallocene catalyst system. However, in a preferred embodiment, pressures of 5 to 20 bar are required; otherwise, the resulting polymers have a very low molecular weight of about 30,000 g / mol.

• ·

SUMMARY OF THE INVENTION

SUMMARY OF THE INVENTION It is an object of the present invention to provide a process for preparing syndiotactic vinylaromatic polymers using metallocene catalysts which does not have the above disadvantages and can be carried out in conventional stirred reactors at low viscosities.

It has been found that this object is achieved by conducting metallocene-catalyzed polymerization of vinylaromatic monomers in dispersion using styrene / diphenylethlenediene block copolymers as dispersants.

Particularly suitable vinylaromatic compounds are those of formula I

where

R is hydrogen or C ₁ -C ₄ alkyl;

R to R ^R 'are independently hydrogen, C - _C? alkyl, C _f - _{C h} -aryl or halogen or two adjacent radicals together are a cyclic group having 4-15 atoms, for example C ·, - CR cycloalkyl, or fused ring systems.

It is preferred to use the vinylaromatic compounds of formula I in which:

R 'is hydrogen.

Particularly suitable substituents R ² to R ⁶ are hydrogen,

C 1 -C ₄ alkyl, chloro or phenyl, biphenyl, naphthalene or anthracene. The two adjacent radicals may also be cyclic groups having from 4 to 12 carbons, so that the compounds of formula I may be, for example, naphthalene derivatives or anthracene derivatives.

Examples of such preferred compounds are:

styrene, p-methylstyrene, p-chlorostyrene, 2,4-dimethylstyrene, 4-vinylbiphenyl, 2-vinylnaphthalene or 9-vinylanthracene.

Mixtures of different vinylaromatic compounds may also be employed, in which case one component may also carry additional hydrocarbon radicals on the phenyl ring, such as vinyl, allyl, methallyl, butenyl or pentenyl groups, preferably vinyl groups. However, it is preferred to use only one vinylaromatic compound.

Particularly preferred vinylaromatic compounds are styrene and p-methylstyrene.

The preparation of the vinylaromatic compounds of formula I is known per se and is described, for example, in Beilstein 5, 367, 474, 485.

Suitable dispersants are block copolymers having at least one pulp block B and at least one block S comprising a copolymer of vinylaromatic monomer of formula (I) and 1,1-diphenylethylene or aromatic ring substituted derivatives thereof, including those substituted with alkyl of up to 22 atoms carbon, as described, for example, in DE-A 44 20 917.

Suitable examples are block copolymers with blocks S and

B of the general structures (SB) _{r 1} , SBS, BSB, X [(SB) J

X [(B-Skk X, S-B-S), ", X (B-S-B), where X is a radical

M-functional condensing agent or m-functional initiator, n is an integer from 1 to 5 and m is an integer from 2 to 20.

In principle, all dienes are suitable as the diene component for block B, although those having conjugated double bonds such as butadiene, isoprene, dimethylbutadiene and phenylbutadiene are preferred. The diene block may be partially or fully hydrogenated or non-hydrogenated. The molecular weights of the Mw of the blocks B are generally from 10,000 to 500,000, preferably from 50,000 to 350,000, and particularly preferably from 70,000 to 250,000 g / mol.

The S blocks consist of a copolymer of a vinylaromatic monomer of formula (I) and 1,1-diphenylethylene or a ring-substituted derivative thereof, including those substituted with up to 22 carbon atoms, preferably 1 to 4 carbon atoms such as methyl, ethyl, isopropyl, n-propyl and η-, iso- or tert-butyl. However, the use of unsubstituted 1,1-diphenylethylene alone is particularly preferred. The proportion of diphenylethylene in block S is from 15 to 65% by weight, preferably from 25 to 60% by weight. The molar ratio of units derived from 1,1-diphenylethylene to units derived from vinylaromatic monomer is generally in the range from 1: 1 to 1: 25, preferably from 1: 1.05 to 1: 15 and particularly preferably in the range from 1: 1, 1 to 1: 10.

The copolymer block S preferably has a random distribution and has a molecular weight M _of generally from 20,000 to 500,000, preferably from 50,000 to 300,000. Especially preferred is the copolymer block S of styrene and 1,1-diphenylethylene.

The ratio of blocks S and B is generally in the range from 90: 10 to: 80, particularly preferably from 90: 15 to 65: 35. The transition of the blocks may be either sharp or gradual. The gradual transition is one where adjacent blocks B and S may also contain monomers of another block in the transition region.

Block copolymers can be prepared by conventional methods of anionic polymerization, as described, for example, in M. Morton, Anionic Polymerization, Principles and Practice, Academic Press, New York 1983. Anionic polymerization is initiated by the action of organometallic compounds. Preferred are alkali metal compounds, especially lithium. Examples of initiators are alkyllithium such as methyllithium, ethyllithium, isopropyllithium, η-, sec- or tert-butyllithium. It is particularly preferred to use n- or s-butyllithium. Suitable solvents are those inert to the organometallic initiator. Aliphatic or aromatic hydrocarbons are particularly suitable. Examples of suitable solvents are cyclohexane, methylcyclohexane, benzene, toluene, ethylbenzene and xylene.

To influence the polymerization parameters, a small amount of polar aprotic substances can be added to the solvents. Examples of suitable substances are ethers such as diethyl ether, diisopropyl ether, diethylene glycol dimethyl ether, diethylene glycol dibutyl ether or, in particular, tetrahydrofuran, as well as tertiary amines such as tetramethylethylenediamine or pyridine. The polar co-solvent is added to the nonpolar solvent in a small amount of from about 0.01 to about 5 volume percent. Tetrahydrofuran in an amount of from about 0.1 to 0.3% by volume is particularly suitable.

In a preferred embodiment of the new process, at least one branching monomer may be utilized.

The branching monomers which can be used are the compounds of the formula II • · [R ^a -] _p -M '

ICH

(III where

^And R is hydrogen, halogen or an inert organic radical having up to 20 carbon atoms, wherein when p> 2, each ^R may be identical or different and the two R radicals ^and can form a 3- to 8- membered ring together with the metal atom, which is and R ^a can also be a common complex ligand when M is a transition metal;

R is hydrogen, C ₁ -C ₄ alkyl or phenyl;

R ^c is hydrogen, C 1 -C ₄ alkyl, phenyl, chlorine or an unsaturated hydrocarbon radical of 2 to 6 carbon atoms;

M is carbon C, silicon Si, germanium Ge, tin Sn, boron B, aluminum Al, gallium Ga, nitrogen N, phosphorus P, antimony Sb, titanium Ti, zirconium Zr, hafnium Hf, vanadium V, niobium Nb, tantalum Ta, chromium Cr, molybdenum Mo, tungsten W, manganese Mn, iron Fe, ruthenium Ru, osmium Os, cobalt Co, rhodium Rh, iridium Ir, nickel Ni, palladium Pd, platinum Pt, copper Cu, zinc Zn or cadmium Cd is 2 to 6;

is 0 to 20;

is 0 to 4;

with the proviso that the sum of η + p corresponds to the valency of M.

• · · · ·

These monomers can be obtained, for example, by reacting the Grignard compounds of chloro (alkyl) styrenes with the corresponding carbon, metal or transition metal compounds, for example halogen compounds. Cases of reactions where M is silicon, germanium or tin are described in K.

Nakanishi, J. Chem. Soc. Perkin Trans I, 1990, p. 3362.

Particularly preferred branching monomer units are those of formula II in which M is carbon, silicon, germanium, tin or titanium, since they are readily obtainable. The m index is preferably from 0 to 8, particularly preferably from 0 to 4.

As branching monomers, for example, titanium [R ^a -] _p -Ti · (CH) containing monomers Ha may be used.

and titanium compounds IIb

Ti (CH

(lib), wherein R 1, R ^b , R ^c , m, n and p are as defined above,

The inert organic radical or radicals R 'is not of great importance in the process. Rather, it serves only to saturate the free valences M and can be selected for ease of availability. Examples of suitable radicals are aliphatic and cycloaliphatic radicals, aryl, hetaryly and aralkyl. Aliphatic radicals include alkyls, alkoxy compounds, alkenyls or alkynyls having, for example, from 1 to 2 or 20 carbon atoms. Cycloaliphatic radicals include cycloalkyls or cycloalkane radicals of 3 to 8 carbon atoms. Instead of methylene in alkyl or cycloalkyl, oxygen in the ether function can also be used. Examples of aryl are phenyl or naphthyl, it is also possible for two phenyls to be oxygen-linked. Examples of aralkyls are C7 -C20 aralkyls, which are based on a combination of phenyl and alkyl. Examples of hetaryl are pyridyl, pyrimidyl and furyl. These radicals may be further substituted, e.g., alkyl, alkoxy, halogen such as fluorine, chlorine or bromine, cyano, nitro, epoxy, carbonyl, ester, amides, ^{etc., and} two radicals R may also form a 3- to 6-membered a ring with an M atom, for example, where two radicals R ^a form an alkylene ring in which one or more CH ₂ groups may also be replaced with oxygen in an ether functionality.

When M is a transition metal, R ^d may also be a complex ligand bonded by a σ- or π- bond such as ethylene, allyl, butadiene or cyclopentadiene, mono- or polysubstituted cyclopentadiene such as methylcyclopentadiene or pentamethylcyclopentadiene, benzene, cyclohexadiene, cycloheptatriene, , cyclooctatetraene, cyclooctatriene, cyclooctadiene, carbonyl, oxalato, cyano, isonitrile, fulminato-C, fulminato-O, cyanato, dinitrogen, ethylenediamine, diethylenetriamine, triethylenetetramine, ethylenediamintetraacetate, nitrosyl, nitrosyl, nitrosyl, nitrosyl, nitrosyl, nitrosyl, nitrosylamino, nitroso, trifluorophosphane, phosphane, diphosphane, arsane, acetylacetonato.

· · · · · · · · · · · · · · · · · · · · · · · ·

R ^b is particularly preferably hydrogen or methyl, R ^c is hydrogen, C 1 -C 4 alkyl such as methyl, ethyl, propyl, isopropyl, n-butyl and isomeric butyls, phenyl, chlorine, or an unsaturated hydrocarbon radical of 2 to 6 carbon atoms such as is vinyl, allyl, methallyl, butenyl or pentenyl.

The branching monomer unit is typically utilized at a molar ratio of vinylaromatic monomer to branching unit of from 10,000,000: 1 to 10: 1.

According to the invention, transition metal complexes of subgroups II to VIII, preferably III to VIII, are used as catalyst component A). Particularly preferred are the metal complexes of titanium, zirconium and hafnium.

If the branching monomer unit of the formula II already contains a transition metal M, in particular titanium, then, depending on the concentration used, it can also be used simultaneously as a catalyst component A in addition to its function as a branching unit.

Particularly preferably, the catalyst components A) are metallocene complexes, especially those having the formula III

where

R 'to R ¹¹ are hydrogen, C - C ₁₀ alkyl, 5- to 7-membered cycloalkyl which may bear Ci - C _F, alkyl as substituents Cf. - Cn, aryl or arylalkyl, and wherein two adjacent radicals may, if desired, together form cyclic groups of 4 to 15 carbon atoms, for example, the fused ring system is [literally] of 4 to 12 carbons, or are Si (R). ¹²⁾ 3 where R ¹² is C _T - C ₁₀ alkyl, C ₆ - C ₅ aryl, or _C3 - Cio cycloalkyl,

M is a metal of Groups III to VI of the Periodic Table of the Elements or is a metal of the lanthanide group,

Z ¹ to Z ³ are hydrogen, halogen, C 1 -C 10 alkyl, C ₆ -C ₁₅ aryl, C 1 -C 10 alkoxy or C 1 -C ₁₅ aryloxy and

OF! up to ₅ are 0, 1, 2, 3, 4 or 5, the sum of Zj + z ₂ + of ₃ + z ₄ + of ₅ corresponds to a valency M minus 1.

Particularly preferred metallocene complexes of formula III are those in which

M is a metal from subgroup IV of the Periodic Table of the Elements,

i.e. titanium, zirconium or hafnium, especially titanium, and

Z ¹ to Z ⁵ are C 1 -C 10 alkyl, C 1 -C ₁₀ alkoxy or halogen.

Examples of such preferred metallocene complexes are:

pentamethylcyclopentadienyltitanium trichloride, pentamethyl · cyclopentadienophenyl · titanium · umtrimethyl and pentamethylcyclopentadienyltitanium trimethylate.

It is also possible to use the metallocene complexes described in EP-A 584 646.

Mixtures of these metallocene complexes may also be used.

• · • · · · ··· ·

Complex compounds of this kind can be synthesized by methods known per se, with the reaction of the corresponding substituted, cyclic hydrogen anions with the halides of titanium, zirconium, hafnium, vanadium, niobium or tantalum being preferred.

Examples of corresponding preparation methods are described, inter alia, in Journal of Organometallic Chemistry, 369 (1989), 359- 370.

As compound B, which forms cations, especially matalocenium ions, the catalyst system may include open chain or cyclic alumoxane compounds.

Suitable examples are open-chain or cyclic alumoxane compounds having the formulas IV or V;

-R (IV) or t-O-Al TV

R ¹³ (V) wherein R ¹³ is C 1 -C ₄ alkyl, preferably methyl or ethyl, when the integer is from 5 to 30, preferably from 10 to 25.

The preparation of these oligomeric alumoxane compounds is usually carried out by reacting a solution of trialkylaluminum with water and is described, inter alia, in EP-A 284 708 and US-A 4 794 096.

in the form of mixtures of both linear and cyclic chains

In general, the oligomeric alumoxane compounds are obtained.

- 13 molecules of different lengths, so k must be reported as an average value. The alumoxanes may also be present in admixture with other metal alkyls, preferably aluminum alkyls.

It has been found advantageous to use the metallocene complexes and the oligomeric alumoxane compound in amounts such that the atomic ratio between the aluminum of the oligomeric alumoxane and the transition metal of the metallocene complexes is in the range of 10: 1 to 10 ⁶ : 1, especially 10: 1 to 10 ^{That made the score 4} - 1.

Coordinating complex compounds selected from the group consisting of strong, neutral Lewis acids, ionic compounds having Lewis acid cations and ionic compounds having Bronsted acids as cations can also be used as the metallocenium ion-forming compound B).

Preferred strong neutral Lewis acids are compounds of formula VI

M ¹ X ¹ X ² X ³ (VI) where

M ¹ is an element of the main group III of the Periodic Table of the Elements, in particular boron B, aluminum Al or gallium Ga, preferably B;

X ^1, X ² and X ³ are hydrogen, C - C _n -alkyl, C ₆ - C ₅ aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl, each having 1 to 10 carbon atoms in the alkyl moiety and 6 to 20 carbon atoms in the aryl, or are fluorine, chlorine, bromine or iodine, especially haloaryls, preferably pentafluorophenyl.

Particular preference is given to compounds of formula VI in which X 1 is X 1 ^. X and X ⁽ are identical; preferably tris (pentafluorophenyl) borane. These compounds and the process for their preparation are known per se and are described, for example, in WO 93/3067.

Suitable ionic compounds having Lewis acid cations are those of formula VII [(Y ^{and +} ) Q1Q2. -Q _z ] ^{d +} (VII) where

Y is an element from the main groups I to VI or subgroups

I to VIII of the Periodic Table;

Qi to Q _z are radicals with a single negative charge, such as C - C ₂ alkyl, C ₆ - C ₁₅ aryl, alkylaryl, arylalkyl, haloalkyl or haloaryl each having from 6 to 20 carbon atoms in the aryl and 1 and 28 carbon atoms; in alkyl,

C 1 -C 10 cycloalkyl, which may be unsubstituted or substituted with C ₁ -C ₁₀ alkyl, or are halogen,

Ci - C ₂ -C 8 -alkoxy, C ₆ - C ₅ aryloxy, silyl or mercaptyl, such as trimethylsilyl, and is an integer of 1 to 6, z is an integer from 0 to 5, and d corresponds to the difference a - z, but it is more or equal to 1.

Particular advantages are achieved by carbonation cations, oxonium cations and sulfonium cations, as well as cations of transition metal complexes. Particular mention is made of triphenylmethyl, silver and

1,1'-dimethylferrocenyl.

Preference is given to noncoordinating counterions, especially boron compounds, as also mentioned in WO 91/09882, preferably tetrakis (pentafluorophenyl) borate.

Ionic compounds with Bronsted acids as cations and preferably also with similar non-coordinating counterions are also specified in WO 93/3067; a preferred cation is N, N-dimethylanilinium.

> Ft * «ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft ft e ft ft ·· ··· · * ··

It has been found that a molar ratio of boron from the metallocene ion-forming compound to the transition metal from the metal complex in the range of 0.1: 1 to 10: 1, preferably in the range of 1: 1 to 5: 1, has been found to be particularly suitable. .

The catalyst system utilized in the novel process may comprise as compound C) an aluminum compound, for example of formula VIII

A1R ¹⁴ R ¹⁵ R ¹⁶ (VIII) wherein

R ¹⁴ to R ¹⁶ are hydrogen, fluoro, chloro, bromo, iodo or

C 1 -C 2 alkyl, preferably C 1 -C ₈ alkyl.

Preferably R ¹⁴ to R ¹⁵ are identical and are C, - _C6 alkyl such as methyl, ethyl, isobutyl or n-hexyl, and ^{the ±} R is hydrogen.

The content of component C) in the catalyst system is preferably from 1: 2000 to 1: 1, preferably from 1: 800 to 1: 10 (the molar ratio of transition metal from compound III to Al from compound VIII).

Aromatic hydrocarbons, preferably those having 6 to 20 carbon atoms, and in particular xylenes, toluene and ethylbenzene, and mixtures thereof, are commonly used as solvents for the metallocene complexes.

The metallocene complexes may be used with or without a carrier.

Examples of suitable carrier materials are silica gels, preferably those having the formula SiO 2. bAlC 8 wherein b is a number from 0 to 2, preferably from 0 to 0.5; i.e. essentially aluminosilicates or silicon dioxide. The carriers preferably have a particle diameter of from 1 to 200 µm, preferably from 30 to 80 µm. These

- 16 • · · ·

Products are commercially available, for example, as silica gel 332 from Grace.

Other carriers include finely divided polyolefins, for example finely divided polypropylene or polyethylene, as well as polyethylene glycol, polybutylene terephthalate, polyethylene terephthalate, polyvinyl alcohol, polystyrene, syndiotactic polystyrene, polybutadiene, polycarbonates and copolymers thereof.

The molar ratio of the transition metal catalyst A) to the vinylaromatic monomer is generally from 1: 1000 to 1: 10 000 000, but preferably from 1: 2000 to 1: 1 000 000.

The process according to the invention is carried out as dispersion polymerization. The dispersant used may advantageously comprise aliphatic hydrocarbons, especially those having 4 to 10 carbon atoms, or mixtures of hydrocarbons. Examples are butane, pentane, hexane and heptane. The concentration of monomers to be polymerized in the dispersion medium is generally from 5 to 65 volume percent, preferably from 10 to 50 volume percent.

The dispersant is preferably used in an amount of from 0.1 to 10% by weight, particularly preferably from 1 to 8% by weight, based on the vinylaromatic compound used. It is preferably dissolved in the vinylaromatic monomer to be polymerized.

Polymerization conditions do not play an essential role. The polymerization is usually conducted at from 50 to 100 ° C at a pressure of from 0.05 to 30 bar, preferably from 0.1 to 20 bar. The polymerization is usually complete after 0.5 to 10 hours. It may be terminated by the addition of protic compounds, for example methanol, and the dispersion medium may be separated by filtration or evaporation and returned to the process.

The new process is technically simple and allows the preparation of vinylaromatic polymers having a high degree of syndiotacticity with low viscosity - less than 4 mPas in conventional stirred vessels. In addition, the polymers are obtained in a particular form. The resulting polymers are suitable for the production of fibers, films and moldings.

A preferred embodiment of this process is to prepare a solution of the dispersant in a vinylaromatic monomer at a concentration of 0.1 to 10 wt%, preferably from 1 to 8 wt%, based on each vinylaromatic compound, and heating the resulting solution, e.g. pentane, e.g. Deň: 29 ° C. Then. a calculated amount of catalyst component is added and the polymerization is carried out at 60-70 ° C and allowed to proceed to completion (about 1 hour) before being terminated with methanol.

The dispersion medium can be removed by filtration or evaporation and the resulting solid can be dried under reduced pressure. If desired, the polymer can be purified by conventional methods of plastics technology, for example by precipitation or washing with acids or alkalis.

DETAILED DESCRIPTION OF THE INVENTION

Purification of 1,1-diphenylethylene (DPE)

Crude DPE (Aldrich or prepared by reaction of phenylmagnesium bromide with acetophenone, acetylation with acetic anhydride and thermal removal of acetic acid) was distilled to 99.8% purity on a column having at least 50 theoretical plates (rectification column; for a larger amount with a Sulzer packed column). The distillate, which is usually pale yellow, was purified by filtration through a 20 cm allox column (alumina for Woelm chromatography, anhydrous), titrated with 1.5 N sec. The resulting product was completely colorless and could be used directly in anionic polymerization.

Purification of monomers and solvents

The cyclohexane (Η) used as solvent was dried over anhydrous alumina and titrated with sec-butyllithium adduct and

1,1-diphenylethylene until a yellow color is obtained. Butadiene (Bu) was distilled from triisobutylaluminium, 1,1-diphenylethylene (DPE) from sec-butyllithium (s-BuLi). A 0.5 molar solution of s-BuLi in cyclohexane was used as initiator. Styrene (S) was dried over alumina immediately before use.

All polymerizations were performed under purified nitrogen with strict exclusion of air and moisture. The reactors were prepared before loading for several hours with a solution of 1,1-diphenylehylene and sec-butyllithium in cyclohexane at reflux.

In the examples below, Bu is 1,3-butadiene,

S is styrene and DPE is 1,1-diphenylethylene. The ratios are by weight.

Preparation of Bu-S / DPE block copolymers

Disperser Dl

7.1 L of cyclohexane and a few drops (about 2 mL) of DPE were charged to a 10 L stirred reactor and titrated with a 0.278 molar sec-butyllithium solution until the mixture began to flush. After addition of 15.1 ml (4.2 mmol)

A 0.278 molar sec-butyllithium solution was added 1.6 L (19.4 mol) of 1,3-butadiene in portions (100 mL) over one hour at 70 ° C and the mixture was polymerized at 70 ° C for an additional hour. The molecular weights of the resulting polybutadiene block were determined on a sample by gel permeation chromatography (GPC), calibrated with polybutadiene:

M "= 248 000 g / mol, M _w / M _n = 1.28, M (maximum peak) =

226,000 g / mol). To the resulting polybutadiene block, 98.3 ml (0.56 mol) was added gradually over 15 minutes.

1,1-diphenylethylene and 259 ml (2.25 mol) of styrene and polymerization was continued at 70 ° C for a further 5 hours. After completion of the reaction, the reaction mixture was titrated with ethanol until it became colorless and was acidified with CO ₂ / water. The colorless solution was stripped of solvent under reduced pressure in an extruder to remove volatiles and the product was subjected to granulation.

GPC (polybutadiene calibration): two peaks: first peak (20%)

M (peak peak = 32,000 g / mol; second peak (80 L): peak peak at 260,000 g / mol).

Disperser D2

In a similar manner to the use of dispersant D1, 1.6 L of 1,3-butadiene, 98.3 ml were polymerized

1,1-diphenylethylene and 259 ml (2.25 mol) of styrene, the polymerization was initiated with 10 ml (2.78 mmol) of a 0.278 mol solution of sec-butyllithium.

GPC of polybutadiene block (polybutadiene calibration):

M. ,, = 441,000 g / mol, M _w / M "= 1.25,

M (peak peak) = 352,000 g / mol

GPC block copolymers (polybutadiene calibration): two peaks, first peak (20%) M (peak peak) = 61,000 g / mol; second peak (80%): peak peak at 411,000 g / mol.

Disperser D3

1.2 L (14.5 mol) of 1,3-butadiene, 73.6 ml (0.42 mol) of 1,1-diphenylethylene and 194 ml (1.69 mol) of styrene were polymerized in the same manner as for dispersant D1, polymerization was initiated with 7.5 ml (2.08 mmol)

0.278 molar solution of sec-butyllithium.

GPC of polybutadiene block (polybutadiene calibration): M _w = 379 000 g / mol, M _w / M _n = 1.30,

M (peak peak) = 324,000 g / mol

GPC block copolymers (polybutadiene calibration): two peaks, first, peak (30%) M (peak peak) = 57,000 g / mol; second peak (70%); peak peak at 394,000 g / mol.

Preparation of S / DPE-BU-S / DPE triblock copolymers

Disperser D4

1.08 l (13.1 mol) of 1,3-butadiene, 149.5 ml (0.85 mol) of 1,1-diphenylethylene and 252.4 ml (2.2 mol) were polymerized in the same manner as for dispersant D1. styrene, polymerization was initiated with 49.1 ml (13.7 mmol)

0.278 molar solution of sec-butyllithium. The polymerization was not terminated with ethanol, but instead was added within 5 minutes.

solution of 0.5 g of ethyl formate (condensing agent) in 10 ml of cyclohexane. Processing was described for dispersant 1.

GPC block copolymers (mixed calibration for polystyrene and polybutadiene 40:60): two peaks, first peak (10%)

M (peak peak) = 79,000 g / mol; second peak (90%); peak peak at 160,000 g / mol.

Example 1

250 ml of n-hexane and a mixture of 2.61 g of dispersant D1 in 104.2 g (1 mol) of styrene were introduced with stirring into a 2 liter stirred reactor and heated to 60 ° C. 8.16 ml of a 1.53 molar solution of methylamoxane (MAO) in toluene (obtainable from Witco), 2.08 ml of a 1.0 molar solution of diisobutylaluminium hydride (DIBAH) in cyclohexane (obtainable from Aldrich) and 9.5 mg were added. (0.04 mmol) of pentamethylcyclopentadienylthiatitanium trimethyl Cp * TiMe ₃ . After 5 minutes a milk dispersion formed. The viscosity of the dispersion remained below 1.4 mPas during the reaction time. After 2 hours, the polymerization was stopped by the addition of 10 ml of methanol and the reaction mixture was filtered off. The filter residue was washed with methanol and dried at 50 ° C under reduced pressure.

The amount of dispersant was 2.5% by weight, based on the amount of styrene used. The conversion, based on the amount of polystyrene used, was 331. The molecular weight M _w and the molecular weight distribution were determined by high temperature gel permeation chromatography GPC (135 ° C, 1,2,4-trichlorobenzene, standard polystyrene) as

M _w = 201 200, M _w / M _n = 1.9. Syndidotactic content determined by ¹³ C-NMR spectroscopy was 96%. The particle size ranged from 2 to 10 µm and was determined under a transmission microscope (Axiophot from Carl Zeiss) in a polymer sample suspended in immersion oil and placed between two flat slides.

Examples 2 to 5

Example 1 was repeated in each case with 2.5 wt. dispersants D2, D3 and D4 or a 1: 1 mixture of dispersant D1 and D2, based on the amount of styrene used. The results are summarized in Table 1.

Comparative example VI

Example 1 was repeated without using a dispersant. The resulting polymer precipitated after only 10 minutes. The conversion, based on the amount of polystyrene used, was only 16%.

Ex. Disper- gátor M _w [g / mol] M _w / M _n Viscosity [mPas] Conversion m Syndiotak- ticita [%] 1 Dl 201 200 1.9 1, 34 33 98 2 D2 467 400 2.5 2.11 63 95 3 D3 367 800 2, 3 1.96 59 97 4 D1 + D2 (each 1,25% wt.) 441 000 2.7 2.20 72 98

5 D4 501 300 2, 6 2.31 86 96 VI - 248 200 2.1 16 96

Claims (10)

A process for the preparation of polymers of vinyl aromatic compounds in dispersion, characterized in that it is carried out in the presence of a dispersant and a catalyst obtainable from A) a transition metal complex of subgroups II to VIII, B) a cation forming agent and C) if desired aluminum compounds, wherein the dispersing agent used comprises block copolymers having at least one diene block B and at least one block S comprising a copolymer of vinylaromatic monomer and 1,1-diphenylethylene or ring-substituted aromatic derivatives thereof, including those substituted with alkyls of up to 22 carbon atoms. A process according to claim 1, wherein the molar ratio of units derived from 1,1-diphenylethylene to units derived from vinylaromatic monomer in block S of the dispersant is in the range of 1: 1 to 1:25. The process according to claim 1 or 2, wherein the block copolymer comprises polybutadiene or polyisoprene in copolymerized form and the diene block B is partially or fully hydrogenated or non-hydrogenated. Process according to any one of claims 1 to 3, characterized in that the block S of the block copolymer consists of a copolymer of styrene and 1,1-diphenylethylene. Method according to one of Claims 1 to 4, characterized in that the dispersing agent is used in an amount of from 0.1 to 2.5. Up to 10% by weight, based on the amount of vinylaromatic compound used. Process according to one of Claims 1 to 5, characterized in that aliphatic hydrocarbons are used as dispersants. The method according to any one of claims 1 to 6, characterized in that the branching monomer unit comprising at least two vinylaromatic radicals is used in a molar ratio of vinylaromatic monomers to branching units of 10,000,000: 1 to 10: 1. Process according to any one of claims 1 to 7, characterized in that the catalyst component A) used is a metallocene complex of the formula III wherein: R ⁷ to R ¹¹ are hydrogen, C - C ₀ alkyl, 5- to 7-membered cycloalkyl which may bear Ci - C ₆ alkyl groups as substituents, C _e - _{C! 5-aryl} or arylalkyl, and where two adjacent radicals may if desired, together form cyclic groups having from 4 to 15 carbon atoms, or are Si (R ^{1 j} wherein R ¹ 'is C - _C alkyl, C _f) - Cis aryl or C - Cn , cycloalkyl, 2.ξ> Μ is a metal of Groups III to VI of the Periodic Table of Elements or is a metal of the lanthanide group, Z ¹ to Z ⁵ are hydrogen, halogen, C _L - Cio alkyl, C ₆ - C ₅ aryl, Ci - Cio alkoxy or C _- C ₅ aryloxy and Z 1 to z ₅ are 0, 1, 2, 3, 4 or 5, the sum of Z 1 + z ₂ + of ₃ + z ₄ + of ₅ corresponds to a valency M minus 1. The method according to claims 1 to 8, characterized in that the cation forming component B) used comprises cyclic or open-chain alumoxane compounds of formula IV or V R ¹³ O — Al R ¹³ R ¹³ p 13 ^K (IV), that - Al XR ^{13 R} (V), where R ¹³ is C 1 -C ₄ alkyl and m is an integer from 5 to 30. Method according to any one of claims 1 to 8, characterized in that the cation forming compound B) used is a coordination complex compound selected from the group consisting of strong, neutral Lewis acids, ionic compounds having Lewis acid cations and ionic compounds having Bronsted acids such as cations.