WO1999011694A1

WO1999011694A1 - Catalyst system for producing polyalkylene carbonates

Info

Publication number: WO1999011694A1
Application number: PCT/DE1998/002368
Authority: WO
Inventors: Christel Rom; Karl-Heinz Schimmel; Erika Wagenknecht; Sylvia Kogut
Original assignee: Buna Sow Leuna Olefinverbund Gmbh
Priority date: 1997-08-28
Filing date: 1998-08-14
Publication date: 1999-03-11
Also published as: DE19737547A1; EP1012202A1

Abstract

The invention relates to a catalyst system consisting of at least two dicarboxylic acids which can be aliphatic, aromatic or a mixture of the two and which can be combined using a divalent inorganic zinc salt. The inventive catalyst system can be used in the co-, ter-, and block-polymerisation of one or several epoxides with carbon dioxide in a continuous or batch operation to achieve higher yields, especially for commercial use. The resulting polymers are free from by-products to a large extent and are 99 % pure.

Description

Catalyst system for the production of polyalkylene carbonates

The invention relates to a catalyst system for the production of polyalkylene carbonates by co-, ter- and block copolymerization of epoxides with carbon dioxide.

It is known that carbon dioxide can be converted to polymers containing carbonic acid ester groups by anionic polymerization with epoxides. These polymers are known as polyalkylene carbonates or as aliphatic polycarbonates.

S. Inoue et al. already described this polymerization reaction in 1969 (Polymer Letters Vol. 7, pp. 287-292). Zinc and aluminum alkyls reacted with water were used as the catalyst.

These catalyst systems have also been used in US 3,585,168, US 3,900,424 and US 3,953,383.

Further catalyst variants are tin compounds, which are described in EP 0 228 037.

Diethylzinc / phenoisystems are also known and have been described by Inoue et al. (Macromolekules, 4, 658, 1971; Macromolecules, 169, 69, 1973) were also examined.

By Soga et al. (Macrom. Chem. 178, 893, 1978) acetates of the transition metals chromium, cobalt, zinc, nickel, tin and magnesium were used as catalysts for the copolymerization of epoxides and carbon dioxide.

The above-mentioned catalyst systems have considerable disadvantages. When using diethyl zinc, for example, due to its extreme sensitivity to air and water, complex security measures are required. The catalyst efficiencies are max. 2 to 10 g polymer / g catalyst. For acceptable sales, relatively large amounts of catalyst for the action required, which in turn must be removed from the reaction mixture with great effort.

Soga et al. also described zinc carboxylates, made from zinc oxide and various dicarboxylic acids with and without supporting inert metal oxides, as highly effective for the copolymerization of epoxides and carbon dioxide. A number of dicarboxylic acids have been tested for the synthesis of this catalyst system. Only adipic acid and glutaric acid proved to be suitable in principle, the activities achieved being only slightly higher than in the systems mentioned above.

US Pat. No. 5,026,676 describes an improved process for the preparation of zinc carboxylates for the copolymerization of epoxides with carbon dioxide. A catalyst activity of approximately 22 grams of product per gram of catalyst used was achieved. However, this turnover is not yet sufficient for a commercially viable application. In addition, the catalyst systems mentioned still produce too many by-products, such as, for example, the cyclic monomer. This cyclic monomer has a negative influence on the product properties. For example, it seriously lowers the glass point of the polyalkylene carbonate and thus changes certain processing properties and thus disadvantageously also possible applications.

The aim of the invention is to find a catalyst system for the co-, ter- and block copolymerization of one or more epoxides with carbon dioxide, which does not have the disadvantages mentioned.

The object of the invention is to make the catalyst system so multifunctional that it is suitable for carrying out a copolymerization, a terpolymerization as well as for a block copolymerization of one or more epoxides with carbon dioxide. It is also an object of the invention to develop a suitable process for the preparation of this catalyst system, so that a high activity of the catalyst and thus economically sensible polymer conversions with high product purity and interesting property profile for a variety of application options can be achieved.

Surprisingly, the catalyst system according to the invention, consisting of an inorganic zinc compound which is brought into contact with a mixture of at least two dicarboxylic acids, leads to above-average yields of polymers with an excellent degree of purity.

The zinc compounds include, for example, zinc carbonate, zinc hydroxycarbonate, zinc oxide, zinc hydroxide, zinc sulfate and other divalent zinc compounds. Zinc hydroxycarbonate, zinc oxide and zinc hydroxide are preferably used.

The dicarboxylic acid mixture consists of at least two dicarboxylic acids, which can be present aliphatic or aromatic or as a mixture thereof. The dicarboxylic acids can be mixed with one another in any ratio, preferably combinations of three are to be used.

In particular, the aliphatic dicarboxylic acids from C ₂ -C10 and the aromatic dicarboxylic acids phthalic acid, terephthalic acid, preferably isophthalic acid, are suitable. Mellitic acid is also advantageous in small amounts. A special effect with regard to the resulting product properties can also be achieved by adding small amounts of monocarboxylic acids. Monocarboxylic acids of C -C-io, in particular those with an odd C number, can preferably be used for this.

Preparation of the catalyst

In the presence of an aprotic solvent, a mixture of zinc oxide (> 99%) or another zinc compound mentioned above with a mixture of at least two finely ground (<15 ηm) dicarboxylic acids are in a three-necked flask, the molar fraction of the zinc compound in this mixture always <0.5 must be submitted. The liquid monocarboxylic acids are slowly added via a dropping funnel. The solvent used should form an azeotrope with water or be immiscible with it, since the water of reaction formed must be removed.

The three-necked flask is equipped with a stirrer, reflux cooling, water separator and gas inlet valve. The gas space is then flushed several times with nitrogen. The reaction mixture is stirred for 90 minutes at room temperature, then the temperature is raised to 53 ° C. and held for about 3 hours with vigorous stirring.

It is also possible to carry out the reaction at 25 ° C. for about 7 hours, also with vigorous stirring. Depending on the composition of the dicarboxylic acid mixture, reaction temperatures between 15 ° C. and 80 ° C. and reaction times of up to 10 hours are possible.

After the reaction time, if appropriate after cooling, the solid is filtered off and dried in a drying cabinet under vacuum at 120 ° C. for 12 hours. The product is a fine white powder and can be stored in tightly closed containers for a long time. After a longer storage period, it is advisable to temper the catalyst again in a vacuum drying cabinet at 120 ° C. for 5 hours before use.

In order to test the effectiveness of the catalyst, the following procedure can be followed.

The catalyst and a suitable solvent, in which the resulting polymer advantageously dissolves, are placed in a pressure reactor rinsed several times with carbon dioxide. The solid catalyst can be metered in as a suspension with the solvent, for example via a lock, or it is filled in dryly before the solvent through a metering opening. The epoxy is then charged. Finally, the reaction mixture is saturated with carbon dioxide with stirring for 30 minutes. Then the reaction quickly brought to the appropriate polymerization temperature. If necessary, carbon dioxide must be replenished during the reaction. After the reaction is complete, the reaction mixture is cooled and let down, the catalyst is separated off mechanically or removed by washing with dilute sulfuric acid. The resulting polymer is finely divided with a suitable precipitant, such as ethanol and dried. The residual solvent content in the polymer must not exceed 5 ppm.

The mass of the resulting polymer is determined by weighing and expressed as the activity of gram of polymer per gram of catalyst, based on the mass of the catalyst used.

The results obtained should be made clear using a few examples.

example 1

For the preparation of the catalyst, 0.45 mol of zinc hydroxide was mixed intensively with 0.4 mol of glutaric acid, 0.07 mol of succinic acid and 0.01 mol of mellitic acid in toluene and then stirred at 60 ° C. for 6 hours. After cooling, the solid was suction filtered and then dried in vacuo at 120 ° C. for 12 hours.

When 16 g of catalyst were used on 400 ml of propylene oxide, which was polymerized with CO ₂ at a pressure of 36 bar and 72 ° C., 460 g of polymer with a purity of 99% were obtained. This corresponds to a catalyst activity of 28.75 g polymer per 1 g catalyst.

Example 2

0.5 mol of zinc oxide was reacted with 0.3 mol of adipic acid and 0.3 mol of glutaric acid. Methylene chloride was used as the solvent. The reaction mixture was stirred at room temperature for 8 hours and then refluxed for 1 hour. The catalyst was worked up as already described in Example 1. 3.5 g of catalyst were used for the copolymerization of 80 ml of propylene oxide with carbon dioxide. The conversion based on the propylene oxide used was 81%. This results in a catalyst activity of 27 g polymer per 1 g catalyst.

Example 3

In a 10 liter pressure reactor, 70 g of a catalyst system prepared by refluxing in toluene from 0.5 mol isophthalic acid, 0.1 mol adipic acid, 0.1 mol succinic acid, 0.3 mol propionic acid and 0.9 mol zinc oxide were used .

6000 ml of methylene chloride and 1500 ml of ethylene oxide were added and then saturated with CO _{2 for} 30 minutes. The reaction mixture was kept at 60 ° C. for 6 hours with vigorous stirring. After cooling and relaxing, the polymer solution was worked up as described above. A conversion based on the ethylene oxide of approximately 80% was achieved. This corresponds to a catalyst activity of 30 g polymer per 1 g catalyst.

Example 4

A carboxylic acid mixture consisting of 0.2 mol of succinic acid, 0.3 mol of adipic acid and 0.1 mol of mellitic acid was mixed intimately with zinc hydroxycarbonate and boiled in toluene under reflux. The temperature was kept at 65 ° C. and the reaction time was 6 hours. The catalyst was worked up as described in Example 1.

19 g of catalyst were used for the polymerization of 400 ml of ethylene oxide with CO ₂ . A conversion based on ethylene oxide of 77% was achieved. This corresponds to a catalyst activity of 28.5 g polymer per 1 g catalyst.

Example 5

To produce a catalyst which was used for the terpolymerization of propylene oxide with ethylene oxide and carbon dioxide, 0.4 mol of glutaric acid, 0.1 mol of succinic acid and 0.01 mol of propionic acid were used as the acid mixture, and 0.45 mol of zinc oxide was used as the zinc compound . The acid component and the zinc oxide was refluxed in toluene for about 5 hours, suction filtered and dried in a vacuum drying cabinet at 130 ° C. for 8 hours.

For the terpolymerization of 150 ml propylene oxide and 150 ml ethylene oxide

13.5 g of catalyst were used for carbon dioxide. 382 g of randomly distributed polymer were obtained. The polymer contained approx. 65% polyethylene carbonate. A catalyst activity of 28 g polymer per 1 g catalyst was thus achieved.

Example 6

Propylene oxide and ethylene oxide were block copolymerized with carbon dioxide, the propylene oxide and 60% of the catalyst which corresponded to that of Example 5 being introduced. The polymerization was carried out under usual conditions. After 3 hours, the ethylene oxide and the remainder of the catalyst were metered into the reactor under pressure. The reaction was complete after a total of 5.5 hours. 360 g of polymer were obtained. When using a total of 12.5 g of catalyst, this corresponds to a catalyst activity of 28.8 g per 1 g of polymer.

Claims

claims

1. Catalyst system for the production of polyalkylene carbonates by co-, ter- and block copolymerization of one or more epoxides with carbon dioxide in a batch or continuous procedure, characterized in that the catalyst mixture consists of at least two dicarboxylic acids which are aliphatic or aromatic or as a mixture thereof can be present and an inorganic zinc compound, which are brought together, the dicarboxylic acids can be mixed in any ratio and the mole fraction of the zinc compound in the catalyst system must always be <0.5.

2. Catalyst system according to claim 1, characterized in that the aliphatic dicarboxylic acids have the C number from C ₂ to C-io and the aromatic dicarboxylic acids are phthalic acid, terephthalic acid or preferably isophthalic acid.

3. catalyst system according to claims 1 and 2, characterized in that the inorganic zinc compound is zinc carbonate, zinc hydroxycarbonate, zinc oxide, zinc hydroxide, zinc sulfate or another divalent zinc salt.

4. catalyst system according to claims 1 to 3, characterized in that the dicarboxylic acids monocarboxylic acids of the C numbers Ci to C10 can be added.