CS232759B1 - Method of polymer preparation with carboxyl end groups - Google Patents

Description

The invention relates to a process for the preparation of carboxyl-terminated polymers by reacting solutions of living polymers, in particular conjugated dienes and / or vinylaromatic compounds containing acids, in particular maleic anhydride and phthalic anhydride.

Live polymers prepared by the action of initiators based on organometallic alkali metal compounds have active carbanions at one or both ends of the chains, convertible in a known manner into other functional groups.

In preparing oligomers or polymers with carboxyl end groups, the living polymers are generally reacted with carbon dioxide (VB 921 803, NSR DAS 1520 468, GDR 139 661, US 3,274,147, US 3,281,335, JAP Pat 70/11153, JAP Depending on the reaction conditions, ketones and tertiary alcohols are also formed in addition to the main product, whereby the carboxyl group content and the functionality of the polymer decrease while simultaneously increasing the molecular weight of the polymer (Wyman, DP et al., J. Pat. Polym Sci (A2, 4545 (1964)).

Optimal conditions for obtaining polymers with carboxyl groups consist in carrying out the reaction at low temperatures, a high excess of carbon dioxide and its high local concentration, at low concentrations of living polymer solutions, and ideally mixing the polymer solution with gaseous carbon dioxide. These reaction conditions are disadvantageous from the point of view of the economics of the carboxylation process of living polymers with carbon dioxide gas, and, as a rule, theoretically possible carboxyl group content is not achieved.

Another possibility to prepare polymers with carboxyl groups is to convert living polymers by reaction with cyclic anhydride carboxylic acids. However, it is known from DE-A-2 061 157 that the reaction of living polymers with cyclic monoanhydrides involves the linkage of the polymer chains with anhydride while opening the ring and adding them to the carbonyl groups of the anhydride. In non-polar solvents, only chain joining takes place, and the polymer chains are free of reactive end groups.

In the presence of polar solvents, such as ethers, although the reaction leading to the termination of the active chain ends to form terminal functional groups is facilitated, the chain linking is not completely suppressed, so that polymers exhibit reduced carboxylic acid content and increased molar mass (NSR DOS 2,061,157, p. 20, Table IV.). Even with an excess of anhydride, for example maleic anhydride, phthalic anhydride or succinic or malonic anhydride, chain-linked polymers are obtained. Also, NSC DAS 1 520 548 describes the coupling of living polymers with cyclic anhydrides.

Thus, according to the prior art, it is not possible to prepare polymers with carboxylic end groups by reacting living polymers with cyclic anhydrides having a carboxyl group content or functionality close to the theoretical value and having a molar mass corresponding to the original living polymer.

These drawbacks of the prior art are alleviated or eliminated in the process for preparing carboxyl-terminal polymers

by reacting groups of solutions of living polymers, in particular conjugated dienes and / or vinylaromatic compounds containing lithium atoms with cyclic carboxylic anhydrides, in particular maleic anhydride and phthalic anhydride, according to the invention, which is added to the living polymer solution before addition sodium or potassium tertiary alkoxide, preferably potassium tertiary butyl alcohol, wherein the molar ratio of alkoxide to lithium is at least 1: 1, preferably 1: 1 to 1.25: 1, the reaction of the anhydride with the living polymer is at a temperature of 263 to 323 K, preferably at 293 to 298 K, and the molar ratio of anhydride to lithium is at least 1: 1.

The amount of alkoxide to be added depends on the number of active centers, but at least a molar ratio of alkoxide to lithium of at least 1: 1 should be maintained. Higher dosages of alcohoxide do not hurt, although high molar ratio of alkoxide to lithium is sufficient 1: 1 to 1: 1.25.

Suitable cyclic carboxylic anhydrides are aliphatic or aromatic monoanhydrides, especially maleic anhydride and phthalic anhydride. The anhydride is metered in at least a stoichiometric amount relative to the lithium introduced into the system by the initiator.

The preparation of living polymers with organolithium initiators takes place under conditions which are known and characteristic of the anionic polymerization. Solvents which are indifferent to the lithium compounds are used, for example n-hexane, n-heptane, benzene or toluene.

The polymerization is carried out at temperatures of from 198 to 423 K, preferably at 273 to 323 K, at atmospheric or elevated pressure. In order to adjust the desired molar mass, a stoichiometric amount of initiator is used in solution polymerization, preferably with a stoichiometric amount of initiator.

They produce polymers having a molar mass of between 1000 and 10,000 g / mol.

Generally known dilithium or polyfunctional organolithium compounds can be used as initiators, for example dilithiobutane, dilithium oligomers of conjugated dienes or reaction products of dilsopropenylbenzene with secondary butyllithium.

In the presence of the initiator solutions as monomers can be polymerized in particular conjugated dienes such as 1,3-butadiene, isoprene, 2 or 3 _J ^^^ i ^ e ^ 1 ^^ ^^ H ^I L L, 3-butadiene, or vinylaromatic compounds such as styrene, alphamethylstyrene or dlvinylbenzene.

An advantage of the process according to the invention is that the conversion of the living polymers of conjugated dienes and / or vinyllarnates by reaction with cyclic carboxylic anhydrides into reactive end group polymers is carried out in a high yield of these groups. The efficiency of introducing reactive groups and their high content in the polymer is substantially increased. Chain coupling reactions in the derivatization of living polymers with cyclic anhydrides are also avoided and polymers with almost theoretical carboxyl group content can be prepared.

The method of the invention is further elucidated by the following example of a specific embodiment, wherein samples 1 and 2 serve for comparison with the prior art method.

Example

In a known manner, living polybutadiene was prepared using an oligoisoprendilithium solution having an oligomerization degree of 6 in benzene and the following formulation:

1,3-butadiene 108.0 g benzene 490.0 ml oligoisoprendilithium 216.0 mmol temperature 283.0 K initiator dosing time 2,0 h time to respond 0.5 h

After the preparation of the living polybutadiene solution was completed, the solution was divided into two portions. To one of them was added potassium tert-butyl alcohol in a molar ratio of K: Li = 1: 1, the other was further processed without treatment. One part of the solution not containing potassium tertiary butyl alcohol is carboxylated by mixing with a 20% solution of maleic anhydride in tetrahydrofuran at a maleic anhydride: Li = 1: 1 molar ratio (sample number 1), the other part carboxylated with a 20% solution of phthalic anhydride in. tetrahydrofuran at an anhydride: Li = 1: 1 molar ratio (sample # 2J).

Similarly, a solution containing potassium tertiary butyl alcohol was carboxylated under the same conditions with maleic anhydride in tetrahydrofuran (sample no. 3) and phthalic anhydride in tetrahydrofuran (sample no. 4). The reaction conditions and results are summarized in the following table.

Sample no. 1 2 3 4 lithium in living polymer (mmol) 54.00 54.00 54.00 54.00 potassium tertiary butyl alcohol (g) - - 6.07 6.07 maleic anhydride (g) 5.3 - 5.3 - phthalic anhydride (g) - 8.00 - 8.00 temperature (K) 298,00 298,00 298,00 298,00 content of carboxyl groups (%) 4.01 3.94 8.91 8.78

The carboxylated polymers are obtained as a white solid gel and are converted to the carboxylic acids with ether-dissolved hydrochloric acid, whereby the polybutadiene with carboxyl end groups is completely dissolved again and lithium chloride is separated. Excess hydrogen chloride is neutralized with solid sodium and collected by centrifugation together with lithium chloride. After stabilizing the polymer solution with 1 part by weight of 2,6-di-tert-butyl-p-cresol, the solvent is removed in a vacuum rotary evaporator.

The carboxyl group content was determined by acldometric titration.

Claims (1)

SUBJECT Process for preparing carboxyl-terminated polymers by reacting solutions of living polymers, in particular conjugated dienes and / or vinylaromatic compounds containing lithium atoms with cyclic carboxylic anhydrides, in particular maleic anhydride and phthalic anhydride, characterized in that tertiary anhydride is added to the living polymer solution BACKGROUND OF THE INVENTION sodium or potassium alkoxide, preferably potassium tertiary butyl alcohol, wherein the molar ratio of alkoxide to lithium is at least 1: 1, preferably 1: 1 to 1.25: 1, the reaction of the anhydride with the living polymer is at a temperature of 263 to 323 K preferably at 293 to 298 K, and the molar ratio of anhydride to lithium is at least 1: 1.