Modifiers for anionic polymerization

Details Modifiers for anionic polymerization Modifiers for anionic polymerization

2001-11-06

2003-06-24

Davis, Brian (Department: 1621)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

Polymers from only ethylenic monomers or processes of...

C564S306000, C564S346000, C564S431000, C564S434000, C564S453000, C564S454000, C564S457000, C564S461000, C564S462000, C564S503000, C564S504000, C564S508000

Reexamination Certificate

active

06583246

ABSTRACT:

FIELD OF THE INVENTION
The invention provides modifiers for the anionic polymerization of conjugated dienes or of conjugated dienes with vinylaromatic compounds.
BACKGROUND OF THE INVENTION
It is known that the anionic polymerization of conjugated dienes, optionally in combination with other unsaturated compounds such as vinylaromatic compounds, is performed in the presence of a so-called modifier in order, for example, to regulate the concentration of vinyl groups in the polymer since, inter alia, the glass transition temperature and thus other properties such as rolling resistance and wet-skid resistance, which are important when making tires, can be affected via the vinyl concentration of the polymer.
Anionic polymerization is performed in a known manner in an inert organic solvent such as aliphatic or aromatic hydrocarbons, in the presence of organoalkali metal compounds, in particular alkyl lithium compounds, as initiators.
As mentioned, in particular during anionic polymerization, polar modifiers such as ethers and tertiary amines, which function as Lewis bases, are added to the reaction mixture in order to have an effect on the microstructure of the polymers. In this connection, reference is made to EP-A 0 304 589, DE-A 4 234 827, U.S. Pat. No. 4,022,959 and U.S. Pat. No. 5,906,956.
Known polar modifiers have either only ether structures (e.g. tert.-butoxyethoxyethane) or only tert.-a mine structures (e.g. N,N,N′,N′-tetramethylethylene diamine) or are used in the form of cyclic compounds which have a combination of ether and tert.-amine structures (e.g. N-methylmorpholine).
The known above-mentioned polar modifiers, which are bidentate polar Lewis bases, are in particular still worthy of improvement, which relates e.g. to the ratio of modifier to initiator, the build-up of uniform chain statistics at low and at high temperatures and the incorporation of higher concentrations of vinyl groups in the polymer. In addition, known modifiers have the disadvantage that the vinyl concentration falls off drastically at high polymerization temperatures and is thus, subject to a temperature-sensitive microstructure regulation, such that block styrene is often incorporated and that larger amounts of modifier as compared with initiator are required during the preparation of polymers containing large amounts of vinyl units. Another disadvantage is the low boiling point of known modifiers and the poor separation from solvents which is associated with this.
SUMMARY OF THE INVENTION
Thus, the object of the invention was to provide modifiers for the anionic polymerization of conjugated dienes or of conjugated dienes with vinylaromatic compounds which do not have the disadvantages mentioned and, in particular, exhibit advantages with regard to the mode of preparation of the modifier and of microstructure regulation when using very small amounts of modifier and in addition enter into thermally stable coordination with the active anionic chain-ends.
DETAILED DESCRIPTION OF THE INVENTION
Thus, the invention provides modifiers for the anionic polymerization of conjugated dienes or of conjugated dienes with vinylaromatic compounds which are characterized in that they are based on aminoethers of the formula
in which
R
1
and R
2
are identical or different and represent alkyl groups with 1 to 10, preferably 1 to 4 carbon atoms, cycloalkyl groups with 5 to 8, preferably 5 to 6 carbon atoms, aryl groups with 6 to 10, preferably 6 carbon atoms, and aralkyl groups with 7 to 15, preferably 7 to 9 carbon atoms,
X represents
wherein R
3
and R
4
are defined in the same way as R
1
and R
2
and p represents an integer from 1 to 6, preferably 1 to 3,
m is an integer from 1 to 6, preferably 1 to 3, and
n is an integer from 1 to 6, preferably 1 to 3.
According to the present invention, those modifiers with the formulae given below are preferably used:
Modifiers according to the present invention can be prepared, for example, by processes described in the literature (e.g. EP-A 47 67 85, U.S. Pat. No. 3,400,157, U.S. Pat. No. 3,426,072, U.S. Pat. No. 3,480,675 and U.S. Pat. No. 3,957,875).
Modifiers according to the present invention may be used individually or in any combination at all with each other.
Obviously, modifiers according to the present invention may also be used together with randomizers or modifiers disclosed in the literature. Potassium compounds with the following formulae, for example, may be mentioned: R
1
OK, R
2
COOK, R
3
R
4
NK, wherein R
1
, R
2
, R
3
and R
4
are alkyl groups with 1 to 20 carbon atoms, cycloalkyl groups with 3 to 20 carbon atoms, alkenyl groups with 2 to 20 carbon atoms, aryl groups with 5 to 20 carbon atoms or phenyl groups.
Examples of R
1
OK are potassium salts of monohydric and polyhydric alcohols such as methanol, ethanol, n-propanol, isopropanol, tert.-butyl alcohol, tert.-amyl alcohol, hexanol, cyclohexanol, 2-butenol, 4-methylcyclohexanol, 3-cyclopentenol, 3-hexenol, allyl alcohol, 1,3-dihydrohexane, 1,5,9-trihydrotridecane, benzyl alcohol, phenol, catechol, pyrogallol or 1-naphthol.
Examples of R
2
COOK are potassium salts of monobasic or polybasic carboxylic acids such as lauric acid, palmitic acid, stearic acid, sebacic acid, phenylacetic acid, benzoic acid, phthalic acid or 1,8,16-hexadecanetricarboxylic acid.
Examples of R
3
R
4
NK are potassium salts of secondary amines, in particular potassium salts of dimethylamine, di-n-butylamine, methyl-n-hexylamine, di(3-hexenyl)amine, diphenylamine or dibenzylamine. In this connection, reference is made to U.S. Pat. No. 5,550,200, U.S. Pat. No. 3,294,768, EP-A 0,603,886 and U.S. Pat. No. 3,674,760.
In addition, modifiers according to the present invention may be mixed with modifiers which contain either only nitrogen or only oxygen as the heteroatom, e.g. with N,N,N′,N′-tetramethylethylenediamine, trialkylamines, N-methylmorpholine, N-phenylmorpholine, tetrahydrofuran, dioxan, diethylene glycol dimethyl ether and/or diethyl ether as are described e.g. in EP-A 0 304 589, DE-A 4 234 827, U.S. Pat. No. 4,022,959, U.S. Pat. No. 5,906,956.
The most suitable mixing ratio in a particular case can easily be determined by appropriate preliminary trials and is governed, inter alia, by the desired ultimate use of the polymers and by the desired structure for the microstructure.
Tridentate modifiers according to the present invention, which have a combination of tertiary amine groups and ether structural units, are used to prepare polymers based on conjugated dienes or copolymers based on conjugated dienes and vinylaromatic compounds.
Polymerization or copolymerization of the monomers mentioned is performed in the conventional way in a suitable solvent in the presence of organoalkali metal compounds as initiators, preferably alkali-lithium compounds such as methyl lithium, ethyl lithium, isopropyl lithium, n-butyl lithium, sec.butyl lithium, n-hexyl lithium, tert.octyl lithium, n-decyl lithium and aryl lithium compounds such as phenyl lithium, naphthyl lithium, 4-butylphenyl lithium, 4-phenylbutyl lithium and cyclohexyl lithium, wherein n-butyl lithium and sec.-butyl lithium are more preferred. The amount of lithium catalyst is governed by the type of organolithium compound and the molecular weight of the polymer being prepared.
Suitable inert organic solvents are: hydrocarbons with 5 to 12 carbon atoms, e.g. pentane, hexane, heptane and octane, and also their cyclic analogues. In addition, aromatic solvents, such as benzene or toluene, are also suitable. Obviously, mixtures of the previously described organic solvents may also be used.
Anionic polymerization is performed, as is well-known, at temperatures in the range 5° C. to 130° C.
The amount of organoalkali metal compounds is governed in particular by the molecular weight, which it is intended to set for the polymers. The most beneficial amount can easily be determined in preliminary trials.
Suitable conjugated dienes which can be used in the polymerization procedure are e.g.: 1,3-pentadiene, 2,3-dimethyl-1,3-butadiene, 2-ethylbutadiene, pipe

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