Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2001-11-14
2003-02-11
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S134000, C526S148000, C526S153000, C526S159000, C526S161000, C526S169000, C526S169200, C526S335000, C526S340200, C525S053000, C525S268000, C525S315000, C525S316000, C525S942000
Reexamination Certificate
active
06518379
ABSTRACT:
The present invention relates to a process for polymerizing dienes in a solvent comprising vinylaromatic monomers and to a process for preparing high-impact polystyrene, acrylonitrile-butadiene-styrene copolymers or methyl methacrylate-butadiene-styrene copolymers.
Various continuous and batchwise, solution or suspension processes are known for preparing high-impact polystyrene. In these processes, a rubber, usually polybutadiene, is dissolved in monomeric styrene which has been polymerized in a prereaction to a conversion of about 30%. The formation of polystyrene and the simultaneous decrease in the concentration of monomeric styrene results in a change in the phase coherence. During this event, known as “phase inversion”, grafting reactions occur on the polybutadiene, and these together with the intensity of stirring and the viscosity influence the nature of the dispersed soft phase. In the subsequent main polymerization, the polystyrene matrix is built up. Such processes carried out in various types of reactor are described, for example, in A. Echte, Handbuch der technischen Polymerchemie, VCH Verlagsgesellschaft Weinheim 1993, pages 484-89 and in U.S. Pat. Nos. 2,727,884 and 3,903,202.
In these processes, the separately prepared rubber has to be laboriously broken up and dissolved and the resulting polybutadiene rubber solution in styrene has to be filtered prior to the polymerization in order to remove gel particles.
Various attempts have therefore been made to prepare the necessary rubber solution in styrene directly by anionic polymerization of butadiene or butadiene/styrene in nonpolar solvents, for example cyclohexane or ethylbenzene, and subsequent addition of styrene (GB 1 013 205, EP-A-0 334 715 and U.S. Pat. No. 4,153,647) or by incomplete reaction of butadiene in styrene (EP-A 0 059 231, EP-A 0 304 088). The block rubber prepared in this way either has to be purified by precipitation or else the solvent and other volatile substances, in particular monomeric butadiene, have to be distilled off. In addition, owing to the high solution viscosity, only relatively dilute rubber solutions can be handled, which leads to high solvent, purification and energy costs.
U.S. Pat. No. 3,299,178 describes a process for polymerizing butadiene in styrene solution in the presence of a catalyst system comprising aluminum alkyls and titanium tetraiodide or titanium tetrachloride and iodine. However, a high halogen content leads to corrosion problems in the further processing of the rubber solution. The catalyst therefore has to be removed, which costs money.
WO 98/07765 and WO 98/07766 describe anionic polymerizations of butadiene in styrene. The anionic polymerization of styrene proceeds very quickly. For this reason, alkyls of alkaline earth metals, zinc and aluminum were used as retardant additives. The additives described have a retarding effect both on the polymerization of butadiene and on the polymerization of styrene. Without addition of randomizers, the anionic polymerization of a monomer mixture of styrene and butadiene initially gives a virtually pure homopolybutadiene block. To slow the subsequent styrene polymerization to a rate which can readily be controlled in industry, the additives have to be added in such amounts that the polymerization rate of butadiene is reduced too much and the overall process becomes uneconomical.
It is an object of the present invention to find a process for polymerizing dienes in a solvent comprising vinylaromatic monomers which leads to diene rubbers having a low incorporation of vinylaromatic monomers together with high butadiene conversions. The diene rubber solutions should as far as possible be able to be used directly, i.e. without removal of catalyst residues, degassing of unreacted dienes or precipitation of the diene rubber, for preparing impact-modified styrene polymers.
We have found that this object is achieved by a process for polymerizing dienes in a solvent comprising vinylaromatic monomers, wherein the polymerization is carried out in the presence of
a) an organometallic compound of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, or W as catalyst,
b) a Lewis acid as cocatalyst,
c) if desired, an alkylating agent and
d) if desired, a regulator.
The solvent preferably consists of from 85 to 100% by weight of vinylaromatic monomers and from 0 to 15% by weight of toluene, cyclohexane, methylcyclohexane, ethylbenzene or DECALIN® (decahydronaphthalene).
As catalyst, preference is given to using a metal chelate complex of Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, or W having at least one chelating ligand bound via two O atoms, two N atoms or one O atom and one N atom. The chelate complex preferably has one or two chelating ligands. Preferred catalysts are metal chelate complexes of the formula (I), (II) or (III)
where
R
1
, R
2
, R
3
, R
4
and R
5
are, independently of one another, hydrogen, unsubstituted or halogen- or alkoxy-substituted C
1
-C
20
-alkyl, C
7
-C
20
-arylalkyl, C
6
-C
22
-aryl or alkylaryl, C
3
-C
15
-cyoloalkyl or alkylcycloalkyl, C
1
-C
20
-alkoxy, C
3
-C
15
-cycloalkoxy, C
6
-C
22
-aryloxy or together with one or more of C
1
, C
2
, C
3
, O and N form a monocyclic, bicyclic or heterocyclic, aliphatic or aromatic ring system having from 3 to 15 ring atoms,
M is Ti, Zr, Hf. V, Nb, Ta, Cr. Mo, W.
X is an anion,
D is an uncharged donor ligand,
n is 1, 2, 3 or 4,
m is the valence of M,
k is an integer or fraction in the range from 0 to 10.
R
1
, R
2
, and R
3
can be, independently of one another, hydrogen, methyl, i-propyl, t-butyl, cyclohexyl, methoxy, ethoxy, i-propoxy, t-butoxy, cyclohexoxy, phenyl, 2,6-di-tert-butylphenyl, 2,6-di-tert-butyl-4-methylphenyl, phenoxy, 2,6di-tert-butylphenoxy, 2,6-di-tert-butyl-4-methylphenoxy and R
4
and R
5
can be, independently of one another, hydrogen, methyl, i-propyl, t-butyl, cyclohexyl, phenyl, 2,6-diisopropylphenyl, 2,6-di-tert-butylphenyl, 2,6-di-tert-butyl-4-methylphenyl.
Examples of suitable anions X are unsubstituted or halogen- or alkoxy-substituted C
1
-C
20
-alkoxides, C
3
-C
15
-cycloalkoxides, C
6
-C
22
-arylalkoxides, tetraalkylsilyloxy, dialkylamide, bis(trialkylsilyl)amide, halide, sulfonates such as triflates, cyanides, substituted or unsubstituted dialkyl or diaryl phosphates having from 1 to 20 carbon atoms.
Suitable donor ligands D in the formulae (I) to (III) are, for example, tetrahydrofuran, diethyl ether, pyridine, dioxane, tetraxnethylenediamine or triethylamine.
As chelating ligands, it is possible to use, for example, 2,2,6,6-tetramethylheptane-3,5-dione, 2,2,4,6,6-pentamethylheptane-3,5-dione, 1,3-diphenylpropane-1,3-dione, 1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)propane-1,3-dione, 3-phenylpentane-2,4-dione, 1,1,1-trifluoro-4-naphthylbutane-2,4-dione, 3-heptafluorobutyryl-(+)camphor, 1,1,1,2,2-pentafluoro-6,6-dimethylheptane-3,5-dione, tert-butyl salicylate, di-tert-butyl malonate, di(2,6-di-tert-butyl-4-methylphenyl)malonate in deprotonated form.
Particular preference is given to using a titanium compound as catalyst, in particular bis(2,2,6,6-tetramethyl-3,5-heptanedionato)Ti(IV) dichloride, (2,2,6,6-tetramethyl-3,5-heptanedionato)Ti(III) dichloride (THF adduct), (2,2,6,6-tetramethyl-3,5-heptanedionato)Ti(IV) triisopropoxide, (2,2,6,6-tetramethyl-3,5-heptanedionato)Ti(III) diisopropoxide (THF adduct), bis(2,2,6,6-tetramethyl-3,5-heptanedionato)Ti(IV) diisopropoxide or bis(1-(4-tert-butylphenyl)-3-(4-methoxyphenyl)-1,3-propanedionato)Ti(IV) diisopropoxide.
Particularly preferred complexes of the formula (I) are bis(2,2,6,6-tetramethyl-3,5-heptanedionato)titanium(IV) diisopropoxide and bis(2,2,6,6-tetramethylheptane-3,5-dionato)titanium(IV) dichloride.
Preference is given to using a cocatalyst which contains no ionically bound halogen. Examples of suitable cocatalysts are open-chain or cyclic aluminoxane compounds such as methylaluminoxane (MAO), boranes, preferably phenylboranes substituted by fluorine or fluoroalkyl groups, e.g. tris(pentafluorophenyl)borane, and borates such as tetrakis(pentafluorophenyl)borate of noncoordinating counterions, preferably N,N-dim
Demeter Jürgen
Gausepohl Hermann
Jüngling Stephan
Luinstra Gerrit
Moors Rainer
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