DE2447349A1 - PROCESS FOR THE PRODUCTION OF ALIPHATIC POLYCARBONATES AND ALIPHATICAROMATIC COPOLYCARBONATES - Google Patents

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Process for the production of aliphatic polycarbonates and aliphatic-aromatic copolycarbonates

The present invention is a process for the production of aliphatic polycarbonates and aromatic-aliphatic copolycarbonates with terminal aliphatic hydroxyl groups by reaction of aliphatic di- or polyhydroxy compounds and optionally monohydroxy compounds with phosgene and / or carbonic acid diesters of aliphatic and / or aromatic dihydroxy compounds with elimination of hydrogen chloride in a more homogeneous manner Phase, which is characterized in that the reaction in the presence of catalytic amounts of aromatic heterocyclic nitrogen bases or «whose salts are in carried out a temperature range between 40 C and 200 ° C

It is known to use dihydroxy compounds in the presence of at least equimolar amounts of pyridine as hydrogen chloride to condense binding agent at temperatures between 0 ° C and room temperature with phosgene to polycarbonates. (DBP 971 777; H. Schnell, Polym «Reviews Vol. 9, Chemistry and Physics of Polycarbonate, John Wiley & Sons, 1964 p. 11).

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The prior art also includes condensing dihydroxy compounds in the melt with phosgene to form polycarbonates. However, this process has the disadvantage that high temperatures have to be used in order to obtain sufficiently high molecular weight products in economically justifiable times. At high temperatures, however, chlorocarbonic acid esters formed as intermediates decompose into CO ₂ and alkyl halides or HCl and olefins and / or hydroxyl groups still present react with HCl to form alkyl halides. These side reactions lead to halogen or olefin alcohols, which act as chain terminators and lower the yield and molecular weight. (H. Schnell, Polym. Reviews Vol. 9, Chemistry and Physics of Polycarbonate, John Wiley & Sons, 1964 p. 10).

It has also been suggested (U.S. Patents 3,359,242; 3,432 and 3,433,756), initially either mixtures of di- and monohydroxy compounds with phosgene or dihydroxy compounds with chloroformic acid esters of monohydroxy compounds at relatively low temperatures (e.g. 120 ° C) to condense to mixed mono- and dicarbonates and then the polycondensation in the transesterification process with the use of alcohols for the purpose of converting the remaining chlorocarbon groups in the presence of catalysts to be completed at temperatures up to 280 ° C. Products are obtained in this cumbersome way with low chlorine content, but you have to accept various disadvantages. So falls as a significant by-product Amount of dialkyl carbonates, which means a loss of yield. It is also at the high temperatures a certain decrease in molecular weight during the initial esterification stage inevitable, especially if catalysts are used

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which, such as titanates, can already be proven to be at Temperatures of 130 - 150 ° C cause carbon dioxide to be split off from carbonates. After all, it's after this Process not possible to produce polycarbonates which exclusively contain hydroxyl end groups, as a result the transesterification process requires - some of the hydroxyl groups are blocked by the alkyl carbonate group. The process products are therefore suitable for further polycondensation reactions such as the reaction with diisocyanates due to their inadequate OH functionality not suitable.

It has now been found that aliphatic in a simple manner Polycarbonates with low chlorine content, high and reproducible hydroxyl end group functionality and precisely adjustable molecular weights obtained when the polycondensation of the di- or polyhydroxy compounds with phosgene or chlorocarbonic acid esters at moderately elevated temperatures in the presence of only catalytic Amounts of aromatic heterocyclic nitrogen bases or salts thereof.

This is all the more surprising since chlorocarbonic acid esters, which are also formed as an intermediate in the condensation with phosgene, easily split off carbon dioxide under the influence of such nitrogen bases even at relatively low temperatures (above about 50 ° C.) and convert to alkyl halides. (Compt. Rend. 200 , 1768 (1936)). If this secondary reaction also took place in the process according to the invention, then polycarbonates would have to be obtained as process products which carry chloroalkyl end groups to a considerable extent.

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The polycarbonates of the process of the invention, on the other hand, are characterized by significantly lower chlorine contents, than they would without the addition of the catalyst according to the invention would be achieved.

Suitable starting materials for the process of the present invention are on the one hand phosgene and the chlorocarbonic acid esters of aliphatic and aromatic dihydroxy compounds such as ethylene glycol, diethylene glycol, polyethylene glycols, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 2,2-dimethylpropanediol-1,3, 2-ethyl-propanediol-1,3, 2-ethylhexanediol-1,3, thiodiethylene glycol, cyclohexanediol-1,4, cyclohexanedimethanol-1,4 and 1, 3 * m- and p-xylylene glycol, 2,2-bis- (4-hydroxycyclohexyl) -propane ,, tetrachloro-p-xylylene glycol, also the oxethylation and oxypropylation products of dihydric alcohols and phenols such as bisoxäthyIbisphenol A, bisoxachäthyltetrachlorobisphenol-A or bisoxachäthyltetrachlorobisphenol-tetron , Hydroquinone, resorcinol, bisphenol A, 2,2-bis- (4-hydroxy-3,5-dichlorophenyl) propane, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide _S) 4,4'-dihydroxydiphenyl sulfone , cv _s <"L'Bis" (4-hydroxyphenyl) diisopropylbenzene, on the other hand aliphatic Dih Hydroxy compounds as mentioned above, monohydric alcohols such as methanol, ethanol, propanol, isopropanol, butanol, cyclohexanol, octanol, 2-ethylhexanol and dodecanol, and finally polyhydric alcohols that function as branching agents such as glycerol, trimethylolethane, trimethylopropane, pentaerythritol and hexanetriol.

All nitrogen bases can be used as catalysts, which contain the nitrogen atom in an aromatic 5- to 6-membered ring and also have no functional groups have more (e.g. Nl ^ - or OH groups) ,, those with phosgene,

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Chlorinated esters or carbonates under the reaction conditions enter into firm ties. In addition to the nitrogen atom, other heteroatoms can also be present in the Such as oxygen, sulfur or a second nitrogen. The heterocycle can also be condensed with other aromatic heterocycles or aromatic carbocycles.

Examples of such catalysts to be used according to the invention are: pyridine, quinoline, isoquinoline, picoline, acridine, pyrazine, pyridazine, pyrimidine and the corresponding benzoheterocycles, where the benzene ring can be substituted with inert groups such as alkyl, carbalkoxy, halogen, etc., oxazines, Thiazines such as phenothiazine, triazines such as 2,4,6-trimethyltriazine, alkyl, alkoxy, carbalkoxy or halogen-substituted compounds of this type such as 2-methylimidazole and the corresponding benzoheterocycles such as benzimidazole, benztriazole and benzothiazole. Preferably pyridine, quinoline, picoline, imidazoles, benzimidazoles, pyrazoles, triazoles and benzotriazoles are used, "You are in amounts of 0.01 to 5 wt .-%, preferably 0.1 to 2% _f based on the solid polycarbonate employed.

The catalysts used according to the invention are of course immediately converted into their hydrochlorides in the reaction mixture converted. On the other hand, many of the nitrogen bases mentioned are dependent on their base strength and the temperature at a dissociation equilibrium between the salt form and the free base. It is therefore possible without impairing the effects according to the invention, instead of the free ones. Use bases of their salts,

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e.g. hydrochloride, hydrobromide, sulfate, nitrate or those salts from which the hydrochlorides can easily form in the reaction mixture, e.g. formates, acetates, Phosphates, carbaminates or picrates.

The polycarbonates can be produced in solvents, but preferably in the melt. When working in solution, the procedure is that the diol to be reacted is in a solvent at room temperature dissolves, adds the amount of phosgene required for a certain molecular weight, after conversion of the phosgene A vacuum is applied and the condensation is completed with a slow increase in temperature.

In some cases it is advisable to use a low-boiling solvent after the solvent has reacted Remove phosgene and complete the condensation in the melt »

The solvents used should be inert under the conditions of the polycondensation and, if possible, the polycondensation product Dissolve »Suitable are e.g. hydrocarbons such as benzene, toluene, diisopropy! benzene and diphenylmethane, Halogenated hydrocarbons such as methylene chloride, chloroform, chlorobenzene, dichlorobenzene and chloronaphthalene as well as ethers such as diisopropyl ether and anisole.

The simplest, however, is the precondensation of the diol with phosgene (if necessary in the melt) with sufficient low temperature or under sufficient pressure so that no phosgene can escape.

The catalyst is either added to the starting material in each case added after the precondensation at the latest,

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Instead of phosgene, the polycondensations can also use prefabricated chlorocarbonic acid esters of corresponding hydroxy compounds can be carried out. Necessary is this process variant 'when alternating copolycarbonates to be built on the basis of various diols.

The reaction temperatures to be observed are relatively low. Even at room temperature is in liquid systems a rapid evolution of hydrogen chloride can be observed. After the precondensation, however, higher temperatures (approx. up to 200 ° C) required to remove the last residues of hydrogen chloride. The preferred temperature range lies between 50 and 175 ° C, with higher viscosity also above. The hydrogen chloride is used to avoid side reactions either by applying a vacuum or by blowing in an inert gas such as nitrogen as quickly as possible aborted. In this way, if necessary after the condensation, the main amount of the catalyst used can also be used with sufficient Volatility, such as that exhibited by pyridine, can be easily removed.

The process according to the invention can be carried out batchwise as well as continuously.

The yields of polycarbonates are usually almost quantitative. The molecular weight and the end functionality of the process products are determined by the molar ratio of the starting compounds precisely adjustable.

In general, the proportions used are such that polycarbonates with a molecular weight of 400-20,000, preferably 800-5000, particularly preferably 1200-2500, arise.

When using trifunctional and polyfunctional hydroxy compounds branched polycarbonates are obtained. Monofunctional hydroxy compounds, on the other hand, act as chain limiters useful. An addition of such compounds

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leads to polycarbonates, some or all of their end groups are saturated with the rest of these monohydroxyl compounds.

Those producible by the process according to the invention Products can serve as plasticizers or lubricants; however, they are used as ¥ calibrated segments for the manufacture of Polyurethanes of particular technical interest because they only have low chlorine content and their OH numbers are above that Quantity ratio of the starting products can be easily adjusted and reproduced.

Unless otherwise stated, the figures given in the following examples are parts by weight or percentages by weight to understand.

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Example 1a

278 g (2.8 mol) of phosgene are passed into a suspension of 354 g (3 mol) of 1,6-hexanediol in 600 ml of methylene chloride at 5 ° C. over the course of 2 hours. The mixture is stirred for 11/4 hours while the temperature rises to 15 ° C. until the odor of phosgene has disappeared. The solvent and some of the hydrogen chloride are removed under reduced pressure to 20 torr and 0.4 ml of pyridine is added. In the course of 7 1/2 hours, the temperature is allowed to rise continuously from 20 ° C. to 100 ° C. until the initially strong evolution of hydrogen chloride has ended. The residue obtained is a colorless, crystalline polycarbonate of a waxy consistency. The OH number is 49 - 50, the total chlorine content 0.26 %>, -. Content of saponifiable and inorganic chlorine: 0.035 %. Yield: 425 g (98 % of theory),

Example 1b (comparative experiment)

In parallel to the above experiment, a batch is allowed to run without the addition of a catalyst at the same temperature control.

At the same point in time at which the reaction is ended in example 1a, a sample is also analyzed here.

Their total chlorine content is still 1.6%, the content of saponifiable and inorganic chlorine is 1.3 %. The elimination of hydrogen chloride is only complete after a further 13 1/2 hours of reaction time at 100.degree. The total chlorine content is then 0.31 % _t that of saponifiable and inorganic chlorine is 0.081 %; OH number = 48; Yield 425g.

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Example 2a (comparative experiment)

118 g (1 mol) of 1,6-hexanediol are suspended in 500 ml of methylene chloride and 92 g (0.94 mol) of phosgene are passed into this suspension at 0 "-20 ° C. over the course of about 1 hour with stirring. The hexanediol goes After a further half hour, all the phosgene has reacted and the solvent and hydrogen chloride formed are stripped off in a water jet vacuum at 20-30 Torr After 5 hours the chlorine content of the reaction mixture is 2.00 %, a further 5 1/2 hours at 100 ° C bring the evolution of HCl to a practically complete standstill. Nevertheless, the reaction product contains 0.53% chlorine, of which 0.22% are saponifiable.

Example 2b

As in Example 2a, the precondensate becomes the reactant under the same conditions and proportions manufactured.

0.4 g of pyridine are added to the precondensate from which solvent has been removed and the procedure is continued as in Example 1a. .4 hours later 90 ° C are reached at 16 Torr, and the evolution of hydrogen chloride has ceased. After 5 hours the chlorine content is 0.27%, of which only 470 ppm represent saponifiable and inorganic chlorine.

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Example 2c

The experiment is carried out as in Example 2b, but the temperature is increased even more slowly, namely steadily up to 70 ° C. over the course of 12 hours. Then no more hydrogen chloride evolution can be observed. The chlorine content is 0.23 %, of which 680 ppm is inorganic and saponifiable. 142.5 g of a white, solid polycondensate, that is 99 % of theory, with an OH number of 54-55 (calculated from the molar ratio of the products used: 53-54) are obtained.

Example 3

Analogously to Example 1a, 1 mol of a precondensate is produced. 20 g each of the product from which the solvent has been removed are filled into tubes that have gas inlet pipes reaching to the bottom and all of them in a large heating bath immerse.

With the exception of one comparative sample, various catalysts are added to the individual samples, namely in such Amounts that the molar proportion, based on nitrogen, is approximately the same in all cases. Then within Heated to 100 ° C for about an hour, a steady stream of nitrogen of 3-4 bubbles / s through the tubes passed through and the time from heating to the end of the evolution of hydrogen chloride measured by in Periodically with a damp pH paper or an indicator solution checks whether the exhaust gas from the tube is still contains acidic components. The result of these tests is summarized in the following table:

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catalyst

Time Cl (Hours) 8th 0.68 2-3 0.22 4th 0.23 5-6 0.23 .8th 0.65 3-4 0.25 8th 1.8 5-6 0.34 8th 0.54

a)

b) 0.08 g imidazole

c) 0.08 g triazole

d) 0.14 g benzotriazole

e) 0.16 g N-methyl

pyrrolidone

f) 0.09 g pyridine

g) 0.1 g of pyrrolidone
h) 0.14 g of quinoline
ü) 0.14 g of benzamide

These experiments show that the heterocyclic aromatic nitrogen bases have a clearly accelerating effect, the other aromatic but not heterocyclic nitrogen compounds and non-aromatic nitrogen heterocycles is missing. The uncatalyzed comparison sample also needs at least twice the time to the end of the Evolution of hydrogen chloride.

Example 4

In a melt heated to .50 - 60 ° C of 118 g (1 mol) of 1,6-hexanediol, which is located in a tubular reactor, phosgene is slowly introduced with stirring so that as little as possible escapes, and as quickly as possible cooled without the mixture solidifying. After absorbing 4 - 6 g of phosgene, the temperature can rise 30 - 35 ° C. It reached 10 ° C after about 30 g and 0 ° C after the calculated amount (93 g)

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are directed. The mixture is kept at this temperature for about 1-2 hours, no more phosgene is present, most of the hydrogen chloride is blown out with nitrogen, 0.4 g of benzimidazole is added as a catalyst and the mixture is heated to 90-100 ° C., with a vigorous stream of nitrogen flowing through the reaction mixture is directed. After 4-5 hours at 100 ° C, the temperature is increased to 150 160 ° C for 1 hour. The clear yellowish melt solidifies on cooling to give 143 g of an almost colorless solid polycondensate, corresponding to a yield of more than 99 % of theory, with a chlorine content of 0.28 % (of which 0.05 % saponifiable and inorganic chlorine) and an OH -Number of 56 (calculated 54).

Example 5a

A mixture of 22.0 g of 2,2-dimethyl-1,3-propanediol (0.21 mol) and 70.6 g of bisphenol A-bischlorocarbonic acid ester (0.20 mol) is melted, mixed with 0.3 g of pyridine and polycondensed within 6 1/2 hours with stirring at a pressure of 17 Torr with evolution of hydrogen chloride. The temperature is increased from 67 to 175 ° C during this time. The result is a highly viscous, difficult to stir melt. 78.0 g (99 %) of a colorless, translucent and very hard copolycarbonate with a chlorine content of 0.32 % (of which 302 ppm of saponifiable and inorganic chlorine) are obtained.

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Example 5b (comparative experiment)

It is carried out with exactly the same approach and the same conditions as in Example 5a, but no catalyst is used added. After 175 ° C have been reached, the low viscosity melt still develops hydrogen chloride. Further 18 hours at this temperature bring only a slight increase in viscosity with continued evolution of hydrogen chloride. The experiment is terminated and yields a brownish solid resin.

Chlorine content: 7.4 % (thereof 5.8 % saponifiable and inorganic chlorine)

Example 6

A mixture of 46.0 g (0.20 mol) of 2,2-dimethylpropanediol-1,3-bis-chlorocarbonic acid ester and 22.0 g (0.21 mol) of 2,2-dimethylpropanediol-1,3 is melted , mixed with 0.3 g of pyridine and polycondensed within 6 1/2 hours at 17 Torr and a temperature rising from 53 ° C to 152 ° C until the evolution of hydrogen chloride ceases. A colorless, viscous melt is obtained which immediately solidifies in crystalline form on cooling. (M.p .: 105-109 ° C). Yield: 52.5 g (98 % of theory)

Chlorine content: 0.22 % (of which 480 ppm saponifiable and inorganic chlorine)

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Claims (1)

Patent entitlement Process for the production of aliphatic polycarbonates or aromatic-aliphatic copolycarbonates with terminal ends aliphatic hydroxyl groups by reaction of phosgene and / or bischlorocarbonic acid esters of aliphatic and / or aromatic dihydroxy compounds with predominantly polyfunctional alcohols, optionally additionally polyfunctional ones Alcohols and / or monofunctional alcohols in a homogeneous phase with elimination of hydrogen chloride, characterized in that that the reaction at 40-200 ° C in the presence of catalytic amounts of aromatic heterocyclic Performs nitrogen bases or their salts. LeA 16 012 609816/0890