BE579605A - - Google Patents

Description

       

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    "PREPARATION OF POLYCARBONATES".

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   The present invention relates to the preparation of polycarbonates and more particularly relates to improved processes for obtaining high molecular weight aromatic polycarbonates. The invention is particularly concerned with the formation of polycarbonates of bis-phenols, such as those obtained by the phosgenation of alkylidene bisphenols.



   Polycarbonates can be obtained, for example, by adding phosgene to a liquid medium formed by mixing an aromatic diol, such as an alkylidene bisphenol (or other aromatic compound having two hydroxyl groups, for example two phenolic hydroxyl groups directly connected. to nuclear carbon atoms), an aqueous solution of an alkali metal hydroxide and optionally, but preferably, an organic solvent for the water-insoluble and chemically inert polycarbonate.



   A disadvantageous feature of these processes, which manifests itself especially with alkylidene bisphenols, such as bisphenol A, is the slowness with which high molecular weight polycarbonates are obtained. Thus, prolonged agitation of the phosgenated liquid reaction mixtures, prior to obtaining the desired high molecular weight polycarbonates, is often the rule. This may require stirring for 10 hours or more, which stirring may even take several days. Such long stirring times are clearly detrimental to the efficiency and economy of the process. The uniformity and quality of the product tend to vary.

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   By virtue of the present invention, high molecular weight polycarbonate can be prepared much faster, often within hours, for example within one to three hours of stirring after phosgenation.



   Thus, by virtue of the present invention, it is possible to shorten to an appreciable extent the time required for the formation of high molecular weight polycarbonates, particularly in comparison with the prolonged reaction times of 10 hours and more. . The quality and uniformity of polycarbonates are high.



   It has now been discovered that the rate of formation of high molecular weight polycarbonates is greatly accelerated and that other advantages, which will emerge from the remainder of the present description, are achieved by phosgenation of a reaction medium containing monophenate d. 'an aromatic diol. Thus, it has surprisingly been found that by appropriately controlling the alkalinity of a reaction medium (to which phosgene is added) the formation of high molecular weight polycarbonates can be accelerated. Proper adjustment or adjustment of alkalinity requires only the provision of a fraction of the stoichiometrically required amount of alkali to form the diphenate of the aromatic diol.



  The expression “monophenate of an aromatic diol” designates the compound obtained by mixing, in aqueous media, one mole of aromatic diol and one mole of an alkali metal hydroxide (sodium hydroxide), this aromatic diol monophenate being able to be represented stoichiometrically by the following formula:
MO - (Ar) - OH in which Ar is an aromatic ring, in particular a phenyl, diphenyl, alkylidene bisphenol or similar group.

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 ford. M denotes a monovalent metal, such as sodium or potassium, the two groups MO and OH being linked directly to the carbon atom of the aromatic nucleus.



   Thus, the result can be considered as that obtained by replacing one of the two hydrogen atoms of the phenolic hydroxyl groups with a monovalent metal.



   In general, mixing an aromatic diol with alkali metal hydride in a ratio of less than 2 moles of alkali metal hydroxide per mole of diol will result in a liquid medium containing monophenate. aromatic diol. Depending on the relative amount of alkali metal hydroxide, the proportion of aromatic diol which, for the purposes of this discussion, is to be considered to be present as the monophenate in the liquid medium will vary. When the amounts of aromatic diol and alkali metal hydroxide are equimolecular, the monophenate of the diol can be considered as the major form in which the aromatic diol is present.

   When the molar ratio of alkali metal hydroxide to aromatic diol is less than unity, the liquid mixture will contain monophenate and aromatic diol (dissolved to the extent of its solubility). On the other hand, when the alkali metal hydroxide and the aromatic diol are mixed in a ratio of between 1.1 and 1.9 moles of alkali metal hydroxide per mole of aromatic diol, the liquid mixture will consist mainly of aromatic diol monophenate and diphenate.



   Preferably, the reaction mixture contains, when initially phosgenic, in a controlled amount sufficient alkali to form the monophenate of the aromatic diol. In all probability, the reaction mixture

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 continues to contain diol monophenate for an appreciable portion of the phosgenation, i.e. usually for at least 30% and often for up to 80 or 90% of the phosgenation period. At least in the preferred embodiments of the invention, the total amount of sodium hydroxide or analogous alkali incorporated into the reaction mixture does not exceed two moles per mole of aromatic diol until this fraction at least phosgene is added.



   While most aromatic diols are essentially insoluble in water, their corresponding phenates, especially their monophenates, are soluble in water. Accordingly, the present invention which involves the use of monophenate can be characterized as relating to the phosgenation or other formation of polycarbonate from a liquid reaction medium, the aqueous phase of which contains monophenate of the aromatic diol.



   For the preparation of many high molecular weight polycarbonates, a heterogeneous liquid reaction medium, which comprises, for example, immiscible phases, in particular an organic phase and an aqueous phase, favorably influences the process. Heterogeneous liquid reaction media are suitable for carrying out the present invention with particular efficiency.



   Suitable heterogeneous liquid reaction media are obtained by using with water (as supplied by the use of an aqueous solution of an alkali metal hydroxide) an organic solvent insoluble in water. water, chemically indifferent or inert, which is preferably an especially good solvent for the polycarbonate produced. Partially halogenated aliphatic hydrocarbons, particularly suitable for this purpose,

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 normally liquid and substantially insoluble in water, especially chlorinated aliphatic hydrocarbons, such as chloroform, methyl chloride, methylene chloride, ethylene chloride, beta-beta'-dichloro ethyl ether, dichloride acetylene, dichloroethylene, and partially chlorinated propanes and butanes.



  Partially halogenated (chlorinated) aliphatic hydrocarbons having 1 to 4 carbon atoms and in which at least one carbon atom is connected to a hydrogen atom and to a halogen atom (chlorine) are most suitable.



  Other suitable solvents are tetrahydrofuran and cyclohexanone. Other organic liquids substantially insoluble in water, although not being especially good solvents for polycarbonate, including inert aromatic liquids, such as benzene, xylene, toluene, chlorobenzenes and the like. , can also be used.



   Among the high molecular weight polycarbonates possessing particularly precise properties, there may be mentioned those derived from alkylidene bisphenols, in particular from bisphenol A. The high molecular weight polycarbonates prepared by phosgenation of a reaction mixture formed from bisphenol A, d An aqueous solution of sodium hydroxide and a water-insoluble organic solvent for the polycarbonate, such as methylene chloride, are exemplary. These polycarbonates can be represented by the following structural formula:

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 EMI7.1
 where n has a large value, for example of or less
20 to 300.



   Rapid and efficient preparation of such high molecular weight aromatic polycarbonates is possible by the present invention. Other high molecular weight polycarbonates are also obtained with increased ease.



   To illustrate the preparation of high molecular weight alkylidene bisphenol polycarbonates, a liquid medium initially formed from an amount of alkali only sufficient to form bisphenol monophenate is phosgenated. This typically involves charging into a jacketed reactor a suitable solvent for the organic polycarbonate, insoluble in water, such as methylene chloride, and suitably proportioned amounts of bisphenol. A and sodium hydroxide, usually in the form of an aqueous solution of sodium hydroxide. By charging the reactor with less than two moles of sodium hydroxide, usually with an amount of between 0.1 and 1.8 moles of sodium hydroxide, per mole of bisphenol, the initial medium will contain bisphenol monophenate
AT.

   Other expedients are comparable in effect to loading sodium hydroxide and bisphenol A in the specified molar ratio. Thus, instead of loading the materials in question as such, the

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 Bisphenol monophenate can be preformed, or sodium hydroxide and bisphenol A can be mixed before being introduced into the reactor in the specified molar ratio and then charged to the reactor as an aqueous solution containing bisphenol monophenate and optionally suitably proportioned amounts of bisphenol and bisphenol diphenate.



   At least theoretically, the liquid reaction medium, as initially established, does not contain sodium hydroxide as such, but instead contains the bisphenol phenates.



   When the reaction medium is established and contains an appreciable proportion, at least about 3%, and even all of bisphenol A as its mono-phenate, phosgene (gaseous or liquid) is gradually added, usually at a rate of such that all of the phosgen is added within 30 to 200 minutes. Moderate agitation during phosgenation distributes the reagents and disperses the phases. Reaction temperatures are between 0 C and 50 C.



   In general, 2.5 to 4.0 moles or more of sodium hydroxide per mole of bisphenol A represents the total sodium hydroxide requirements necessary for complete conversion of bisphenol A to the desired product.



   Additional sodium hydroxide or an alkali analog of an inorganic nature is therefore added during the formation of the polycarbonate and, preferably, during the phosgenation. The rate of addition of alkali and the amount of alkali added depend, among other things, on the initial charge of alkali metal hydroxide and are preferably chosen so as to maintain specific conditions, such as those. described in more detail below.

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   Substantially complete utilization (substantially complete conversion to polycarbonate) of the bisphenol A charged to the reactor requires about 1.0 to 1.3 moles of phosgene per mole of bisphenol A. The rate of addition of phosgene is, therefore, adjusted so that the required amount is added within 30 to 200 minutes. Thus, bisphenol A monophenate is provided initially, by appropriately adjusting the ratio in which bisphenol A and alkali metal hydroxide are mixed, so as to establish the reaction medium to which phosgene is added. Until at least about 30% of the total phosgene requirement is added, the total amount of alkali metal hydroxide charged to the reaction medium is less than 2 moles per mole of bisphenol A charged.



   According to one embodiment of the present invention, the initial formation of bisphenol A monophenate is accomplished by mixing bisphenol A, methylene chloride or a similar organic solvent and an amount of sodium hydroxide in aqueous solution. sufficient so that the resulting mixture is at a pH of about 11. Pre-phosgenation or initiation of phosgenation is ensured by usually employing about 0.07 moles of sodium hydroxide per mole of bisphenol A. addition of phosgene, which takes 30 to 200 minutes, the reaction medium is maintained at a pH of between 10.8 and 11, by adding additional sodium hydroxide or an alkali anabgue.

   The pH is continuously controlled until an appreciable proportion of all the phosgene has been added, especially until at least about 30% of the phosgene has been added. After that, the remainder of the sodium hydroxide is charged in any suitable manner. The remainder of

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 the sodium hydroxide can be charged as quickly as possible or a pH control can be continued until such control is no longer possible (usually when about 60% of the phosgene has been added).



   Preferably, the remainder of the sodium hydroxide is completely added before the addition of the phosgene is complete.



   In this embodiment, approximately 4% of the bisphenol A is in the form of monophenate in the initial reaction medium. Most of the remaining bisphenol A is undissolved. In contrast, the monophenate is soluble in water and is undoubtedly present in the aqueous phase.



   Much greater proportions of bisphenol A may be initially present as the monophenate in the practice of the present invention. In addition, the remainder of bisphenol A can be present either as bisphenol A or as bisphenol A diphenate.



   Thus, according to another embodiment of the present invention, an initial reaction medium is established by forming a mixture of bisphenol A, a suitable organic solvent, such as methylene chloride, and an aqueous solution of sodium hydroxide, using 1.1 to 1.5 moles of sodium hydroxide per mole of bisphenol A. This amount of sodium hydroxide is sufficient for bisphenol A to be present as a mixture of its mono- and di-phenates. When using a ratio of 1.5 moles of sodium hydroxide per mole of bisphenol A, equimolecular proportions of bisphenol A monophenate and bisphenol A diphenate can be obtained in the initial reaction mixture.



   This medium is then phosgene- A certain time has -

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 Before the end of phosgenation, usually when 30-90% of the phosgene has been added, the rest of the required sodium hydroxide is added. All of the sodium hydroxide can be added at once, or this hydroxide can be added in several smaller fractions.



   In these embodiments, it is common practice to stir the reaction mixture gently after the addition of the phosgene. This agitation continues for only a few hours, usually for less than three hours and often for one to two hours. At the end of the stirring period, high molecular weight polycarbonates are obtained.



   The following examples illustrate how the present invention can be practiced.



   EXAMPLE I.-
68.4 g (0.3 mole) of bisphenol A (p, p'-isopropylidene bisphenol), 180 ml of methylene chloride and 100 ml were placed in a glass bottle with a capacity of 1 liter with five tubes. ml of water. A Beckman Zeromatic pH meter with a socket-type reference electrode and a standard glass electrode was immersed. in the contents of the container to measure the pH.



   Other tubing from the vessel was used for the introduction of metered amounts of gaseous phosgene and sodium hydroxide, as well as for the placement of a paddle stirrer and thermometer.



   The pH of the reaction mixture was then adjusted to 11, by introducing into the flask 7 ml of a 4N aqueous solution of sodium hydroxide. This quantity of sodium hydroxide is sufficient to convert approximately 4.5% of bisphenol A into its monophenate, so as to initially obtain a reaction medium containing sodium monophenate.

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 bisphenol A and bisphenol A. While the contents of the flask were stirred by rotating the stirrer at 300 rpm and maintained at 25 C by cooling in an ice bath, 33.6 g (0.34 mole) of gaseous phosgene dances in the liquid medium within
50 minutes at 0.66 g per minute.

   4N aqueous sodium hydroxide solution was added in amounts necessary to maintain the reaction mixture at a pH of 10.8-11 during the first 33 minutes of the addition of phosgene, the pH readings. being done on the pH meter. At this time, 50 ml of 4N sodium hydroxide solution was charged. The medium was then emulsified.



   The remaining amounts of phosgene and sodium hydroxide were added so that the end of their additions coincided. A total of 210 ml of 4N sodium hydroxide solution was charged. At the end of this period, the chlorine (chloroformate) content was less than 0.001% by weight of the polycarbonate, indicating that a high molecular weight polycarbonate was obtained.



   The emulsion persisted during stirring and was broken up by the addition of dilute hydrochloric acid. After separation of the organic phase, washing to the end of chloride ions, drying over anhydrous sodium sulfate and evaporation, a bisphenol A polycarbonate having a K value of 53 was obtained.



   EXAMPLE II. -
68.4 g (0.3 mole) of bis-phenol A, 180 ml of bisphenol A, 180 ml of methylene chloride, 100 ml of water and 105 ml of a 4N aqueous solution of sodium hydroxide.

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   Use of this amount of sodium hydroxide is sufficient for the bisphenol A to be dissolved in the aqueous phase as a mixture of bisphenol A monophenate and diphenate. The vial was immersed in an ice bath. and, during the reaction, the temperature was kept at 25 C.



   By rotating the agitator at a speed of
At 300 rpm, a total of 33 g (0.33 mol) of phosgene gas was added to the liquid mixture, over 50 minutes, at a uniform rate, except that around the middle of the addition of the phosgene , this addition was stopped for about 3-5 minutes, during which time 105 ml of a 4N aqueous sodium hydroxide solution was added. After the addition of this fraction of sodium hydroxide, the reaction medium was re-emulsified and the phosgenation continued.



   After stirring the reaction mixture for 2 hours after the addition of phosgene was complete, the polycarbonate did not contain detectable chloroformate chlorine. The obtained polycarbonate had a K value of 54.



   The procedure of Example II was repeated, on a larger scale, as follows:
EXAMPLE III. -
A steel tank with a capacity of 20 gallons, equipped with a jacket and an agitator, was charged with 26.4 liters of water, 6.8 kg (30 moles) of bis-phenol. A, and 3.3 kg (42.0 moles) of an aqueous solution of sodium hydroxide containing 50.97% by weight of sodium hydroxide. Using this amount of sodium hydroxide, a reaction mixture was obtained containing about 60% (Immoles) of the bisphenol A charged as monophenate and the remainder (12 moles) as bisphenol diphenate.

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 A. A nitrogen atmosphere was maintained in the vessel.



  After complete dissolution of bisphenol A (and therefore after its conversion to mono- or di-phenate), the reaction mixture was cooled to 25 ° C., circulating a cooling agent through the jacket of the tank. Then 18 liters of methylene chloride were added.



   While maintaining the temperature at 25 ° C and rotating the stirrer at 120 rpm, 1.671 kg (approximately 17 moles) of phosgene gas was added at a substantially constant rate over 36 minutes.



  The supply of phosgene was then interrupted for 10 minutes, during which 3.4 kg (42.0 moles) of an aqueous solution of sodium hydroxide containing 50.91% by weight of NaOH, taking care to maintain the temperature at 25 ° C. During this addition of sodium hydroxide, the mixture emulsified. The addition of phosgene was then resumed, adding an additional 1.699 kg (about 17.0 moles) of phosgene over 50 minutes, at a substantially constant rate.



   After addition of the phosgene, stirring was continued and temperature control was maintained as during phosgenation, for an additional two hours, during which all of the chloroformate had reacted and the formation of polycarbonate. high molecular weight ended. The emulsion was broken up by adding 36 liters of methylene chloride.



  The organic phase was separated, after which it was washed with water until there were no more chloride ions and the polycarbonate was precipitated as a granular product by adding normal heptane to methylene chloride solution.

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   The results of Examples II and III can be repeated, adding the second charge of sodium hydroxide after adding about 30, 40, 60, 70 or 80% of the total phosgene. However, a greater or lesser amount of sodium hydroxide is charged initially. When the second charge is added after adding 30% of the total phosgene, only 30% of the sodium hydroxide is initially charged.



   It will be noted that inorganic alkalis other than sodium hydroxide can be used. Thus, organic alkalis, especially water soluble alkalis, such as potassium hydroxide, lithium hydroxide, sodium carbonate and the like can be added or used in place of sodium hydroxide. or in admixture therewith or with each other.



   In accordance with the present invention, the production of high molecular weight aromatic polycarbonates by the phosgenation of a reaction medium containing the monophenate of an aromatic diol, such as a bis-phenol, is characterized by the low content. chlorine chloroformate from the reaction medium substantially throughout the period of polycarbonate formation. Thus, during substantially the entire reaction period, an appreciable but low chlorine concentration of chlorformate is present in the phosgene reaction medium, this concentration being less than approximately 2% and usually less than approximately 1% relative to the weight of polycarbonate. . This low chlorine content of chloroformate is, therefore, an indication of the execution of the present invention.



   The following examples show the concentration of chlorine chloroformate prevailing in the reaction medium during the preparation of high molecular weight polycarbonates.

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   EXAMPLE IV.-
In a glass bottle with a capacity of one liter with five nipples, equipped with a paddle stirrer, 68.4 g (0.3 mole) of bisphenol A, 180 ml of methylene chloride and 100 ml were charged. ml of water. A Backman Zeromatic pH meter with a standard socket and / or glass electrode type reference electrode was inserted or dipped into the contents of the vial to measure the pH. Other tubing from the flask was used for the introduction of metered amounts of gaseous phosgene and sodium hydroxide and to allow insertion of the stirrer and thermometer.



   The pH of the reaction mixture was then adjusted to 11 by the addition of 7 ml of a 4N aqueous solution of sodium hydroxide. Use of this amount of sodium hydroxide was sufficient to convert about
4,5 of bisphenol A in its monophenate. While the flask was immersed in an ice bath and its contents were maintained at a temperature of 25 C, while the stirrer was rotating at 300 revolutions per minute, 33.6 g (0, 34 mole) of phosgene gas over 50 minutes at 0.66 g per minute. Sodium hydroxide in 4N aqueous solution is then added in amounts sufficient to maintain the reaction mixture at a pH between 10.8 and 11 during the first 33 minutes of the addition of phosgene.

   At this time, 50 ml of 4N sodium hydroxide solution was charged. The mixture or reaction medium was then emulsified.



   After completion of the addition of phosgene and simultaneous but slow addition of the remainder of the sodium hydroxide so that the end of the addition of phosgene corresponds to the end of the addition of sodium hydroxide (d '' a total of 210 ml of hydroxide solution

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 4N sodium), stirring was continued for two hours.



  At the end of this period, the chlorine content of the chloroformate was 0.001% by weight of the polycarbonate.



   The emulsion which remained throughout the stirring was then broken up by the addition of dilute hydrochloric acid, after which the organic phase was separated, washed until it was free of chloride ions. , dried over anhydrous sodium sulfate and evaporated to obtain a bisphenol A polycarbonate having a K value of 53.



   During the addition of phosgene, samples were taken periodically from the reaction medium, the sample volume being 5-10 ml of / the organic phase during the addition of phosgene and 25 ml of the organic phase during the period of. agitation. In the case of emulsions, a large sample, usually 50 ml, was taken and broken up with dilute sulfuric acid.



   After dilution of the organic phase sample, it was washed until it was free of chloride ions, using distilled water, in a separatory funnel. The washed sample was then treated with 3 ml of pyridine in 40 ml of water and stirred vigorously for 5 minutes. It was then acidified with nitric acid and a standard Volhard titration was performed. The weight of the polycarbonate in the titrated sample was determined by treating the sample with concentrated ammonium hydroxide to dissolve any silver salt present before separation of the layers. Evaporation of the organic layer left a residue, which was dried and weighed.

   In this way, the chlorine content of chloroformate was as follows:

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 TABLE I
 EMI18.1
 
<tb> Minutes <SEP> elapsed <SEP> since <SEP> Chlorine <SEP> content <SEP> <SEP> of <SEP> chloro-
<tb>
<tb>
<tb> the <SEP> beginning <SEP> of <SEP> ad- <SEP> formate <SEP> in <SEP>% <SEP> in <SEP> weight <SEP> of
<tb>
<tb>
<tb> <SEP> edition of <SEP> phosgene.- <SEP> polycarbonate. <SEP> -
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 30 <SEP> 1.0
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> 50 <SEP> 0.1
<tb>
 
EXAMPLE V.-
In a glass bottle with a capacity of one liter, three tubes, fitted with a paddle stirrer, 68.4 g (0.3 mol) of bisphenol A, 180 ml of methylene chloride, 100 ml of water and 105 ml of 4N aqueous sodium hydroxide solution were placed.

   The flask was immersed in an ice bath and, during the reaction, the temperature was kept at 25 ° C.



   While rotating the stirrer at 300 rpm, a total of 33 g (0.33 mole) of phosgene gas was added to the liquid mixture, over the course of 50 minutes, at a uniform rate, if not It was that about the middle of the phosgene addition, this addition was stopped for 3-5 minutes, while 105 ml of 4N aqueous sodium hydroxide solution was added. After addition of this sodium hydroxide fraction, the reaction mixture emulsified and phosgenation was continued.



   After stirring the reaction mixture for 2 hours after the addition of phosgene was complete, a polycarbonate was obtained which did not contain detectable chloroformate chlorine. The polycarbonate, obtained recovered by the procedure described in Example I, had a K value of 55.



   During the addition of phosgene, samples were taken periodically from the reaction mixture and analyzed to determine their chlorine content of chloro-.

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 formate as described in Example IV. The results of the analyzes are as follows:
TABLE II.-
 EMI19.1
 
<tb> Minutes <SEP> elapsed <SEP> after <SEP> Content <SEP> in <SEP> chlorine <SEP> of <SEP> chlorol <SEP> beginning <SEP> of <SEP> formate <SEP> in <SEP >% <SEP> in <SEP> weight <SEP> of
<tb> addition <SEP> of <SEP> phosgene <SEP> polvcarbonate
<tb>
<tb> 12.5 <SEP> 0.0
<tb>
<tb> 25.0 <SEP> 0.0
<tb>
<tb> 37.5 <SEP> 0.2
<tb>
<tb> 50.0 <SEP> 0.5
<tb>
 
Considerable latitude is allowed under other reaction conditions.

   Temperatures to maintain a liquid reaction mixture and below the boiling point of the organic solvent are generally suitable. Typical temperatures range from 0 C to 50 C. Higher temperatures, for example, temperatures above the normal boiling point of the solvent (or temperatures above that at which substantial volatilization of the sol occurs). vant) are possible, if one makes use of etahches reactors or if one operates at a pressure higher than the atmospheric pressure.



   The total amount of sodium hydroxide or the like inorganic alkali used in forming any given polycarbonate substantially exceeds the stoichiometric amount. 2.5-4.0 moles of sodium hydroxide or the molar equivalent of another organic alkali are used per mole of aromatic diol, such as bisphenol A.



   Another consideration involved in carrying out the process is the ratio of water to organic solvents. 0.3 to 1.5 volume of organic solvent per volume of water is preferably employed. Ordinarily it

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 It suffices to use an amount of organic solvent sufficient to obtain a polycarbonate content of between 5 and 30% by weight of the organic phase at the end of the formation of the polycarbonate.



   Particularly useful organic solvents are the water-insoluble, normally liquid, chemically inert solvents in which the polycarbonate produced is soluble. Most important of these solvents are the partially halogenated and normally liquid aliphatic hydrocarbons, especially the chlorinated aliphatic hydrocarbons, such as chloroform, methylene chloride, methyl chloride, ethylene chloride, beta. beta'-dicyloroethyl-ether, ethylidene bichloride, dichlorethylene, trichlorethylene, and partially chlorinated propanes and butanes.



  Partially halogenated (chlorinated) aliphatic hydrocarbons having 1 to 4 carbon atoms and in which at least one carbon atom is connected to both a hydrogen atom and a halogen atom (chlorine), are suitable. specially. Partially halogenated more volatile derivatives of ethane and methane, such as methyl chloride, ethyl chloride, monochloro-difluoromethane, can be used, if care is taken to keep the solvent as it is. liquid in the reaction medium.



  Other substantially water-insoluble organic solvents in which the polycarbonates produced are soluble in an amount of at least about 5% by weight are also suitable.



   The best inorganic alkali is sodium hydroxide. However, other especially water soluble inorganic alkalis, such as potassium hydroxide, lithium hydroxide, sodium carbonate and the like can be used in place of the hydroxy hydroxide.

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 of sodium, alone or in mixtures.



   A wide variety of polycarbonates can be efficiently prepared by the process of the invention.



  One of the most important classes of polycarbonates is that of the polycarbonates of alkylidene bisphenols, such as:: polycarbonates of bisphenol A. The invention therefore relates to the preparation of polycarbonates by phosgenation of the following alkylidene bis-phenols and bis-phenols analogues:

   (4,4'-dihydroxy-dipheyl) -methane
 EMI21.1
 11- (4,4'-dihydroxy-diphenyl} -cyclohexane 2,2'-methylene bis (4-methyl-6-tert.butyl phenol) 2,2'-methylene bis (4-ethyl-6-tert.butyl phenol) 4,4'-butylidene bis (3-methyl-6-tert.butyl phenol) 4,4'-thiobis (3-methyl-6-tert.butyl phenol)
 EMI21.2
 1,1- (Y, Y'-dihydroxy-3,3 "-dimethyl-diphenyl) -cyclohexane 2 2- (2 2l.dihydroxy ...

   li -di-t erty-butyl-diphenyl) -propane 3, Y- (Y, 4'-dihydroxy-diphenyl) -hexane 1,1- (4,41-dihydroxy-diphenyl) -l-phenyl-ethane 2, 2- (4,4'-dihydroxy-dipheyl) butane 2,2'- (4,4'-dinhydroxy-diphenyl) pentane
 EMI21.3
 3 3 '- (44' -dihydroxy-.diphenyl) ..pentan e z2t- (44'-dihydroxy-diphenyl) -3-methyl-butane 2,2 '- (Y,%' - dihydroxy-diphenyl) -hexane 22 '- (4.4'-dihydroxy-phenyl) -! + - methyl-pentane 2,2'- (4,4'-dihydroxy-diphenyl) -heptane 4,4'- (4,4'-dihydroxy-diphenyl) -heptane 2,2- (4,4'-dihydroxy-diphenyl) -tridecane 2,2-bis (3,5-dichloro-4-hydroxy phenyl) -propane 2,2-bis (tetrachloro hydroxy phenyl) -propane 2 , 2-bis (3-chloro-4-hydroxy phenyl) -propane
 EMI21.4
 2,2-bis (3,3'-dimet] yi-y, y '% dihydroxy-diphenyl) -propane

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 Furthermore,

   polycarbonates can be prepared using mixtures of two or more of these alkylidene bisphenols.



   In addition to bisphenol polycarbonates, it is also possible to prepare polyhydroxy- and in particular di-hydroxy-benzenes or naphthalene polycarbonates.



  As typical compounds, the following may be mentioned: catechol, resorcinol, quinol, orcinol, mesorcinol, dihydroxy. xylol, thymoquinol; Naphthalene diols, such as 1,3-dihydroxy-naphthalene, 1,8-dihydroxynaphthalene. 16-dihydroxynaphthalene, 2,7-dihydroxynaphthalene; dihydroxydiphenyls such as 2,5-dihydroxydiphenyl, 2,2'-dihydroxydiphenyl, 2,4'-dihydroxydipheyle, 3,3'-dihydroxydiphenyle, 4,4'-dihydroxydiphenyle, 3,4-dihydroxydiphenyle.



   Mixed polycarbonates can also be prepared in accordance with the present invention from combinations of aromatic diols and various polyhydric diols, particularly aliphatic, or cycloaliphatic diols, or alternatively from aralkyl diols.



  Thus, a mixture of bisphenol A or an analogous alkylidene bisphenol and an aliphatic or cycloaliphatic diol can be phosgenated, so as to produce a substantially linear polycarbonate having separate alternating aromatic and aliphatic groups. by carbonate bonds. As examples of cycloaliphatic diols, mention may be made of the following 1,2-cyclohexanediol, 1,3-cy-clohexanediol, 1,4-cyclohexanediol, 1-methyl-cyclohexanediol-2,3, 1,2-cyclopentanediol, 1 , 3-cyclopentanediol, 3,3'-dihydroxydicyclopentyl ether, hydrogenated alkylidene bisphenols such as 4,4'-dihydroxydicyclohexyl-2,2-propane and 1,2-dihydroxy-4-vinylcyclohexane.



   Among the aliphatic dihydric compounds or aliphatic diols, mention may be made of dihydric alcohols

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 saturated acyclics (glycols), such as ethylene glycol, propanediol-1,2, butanediol-1,3, butanediol-2,3, butanediol-1,2, butanediol-1,4, diethylene glycol, triethylene glycol, tetraethylene glycol, dipropylene glycol, tripropylene glycol, dibutylene glycol, tetrabutylene glycol, and olefinically unsaturated dihydric alcohols such as 3-butene-1,2-diol. Polyglycols containing 1 to 4 ether linkages and / or up to 12 carbon atoms, as well as the corresponding thioglycols, such as thiodiglycol, ethylene thiodiglycol, etc. are also included.

   The aralkyl diols, in which the hydroxyl groups are attached to the alkyl substituents are also useful in place of or in combination with the aliphatic or cycloaliphatic diols. Among these compounds, there may be mentioned xylylene glycols, such as phthalyl alcohol, metaxylylene glycol, paraxylylene glycol; dimethylxylylene glycols, such as alpha, alphat-dihydroxy-durene and styryl glycol.



   In order to prepare mixed polycarbonates, for example polycarbonates derived on the one hand from an aromatic diol and on the other hand from a cycloaliphatic or aliphatic diol, the ratio in which the respective diols are employed may vary. Thus, the aromatic diol can constitute from 25 to 90 mole% of the mixture of diols.



  Other polycarbonates can be derived from mixtures of diols, in which the aromatic diol constitutes only 5 to 10 mol% of all the diols.



   Although the present invention has been described primarily with reference to the phosgenation of aromatic diols alone or in admixture with other diols, bishaloformates and especially bischloroformates can be used. Thus, bischloroformate of bis-

 <Desc / Clms Page number 24>

 phenol A can be used in place of or in admixture with phosgene, to provide high molecular weight polycarbonates, by reaction with a mixture of bisphenol A and an alkali metal hydroxide solution.



  Mixed polycarbonates can be prepared from diethylene glycol bis-chloroformate and bis-phenol A.



   The present invention is thus applicable to the preparation of polycarbonates by a type of reaction which can be regarded as directly or indirectly reacting (or consuming) a series of carbonic acid halide (preferably chloride) groups, such as those provided by phosgene (or another carboxylic halide) or by a bischloroformate (or another bishaloformate, such as bromofluoro- or iodoformates) and a series of hydroxyl groups, at least part of which is provided directly or indirectly by an aromatic diol, so that a multiplicity of carbonate bonds is formed in the polycarbonate.



  Generally speaking, this overall effect can be illustrated as follows:
 EMI24.1
 In this relation n is equal to 2 or more and x has a large value.



   Considered from this point of view, the formation of polycarbonates by the process according to the invention is the consequence of the interaction between polyfunctional compounds, which unite (directly or indirectly) reactive carbonic acid halides and groups. phenolic hydroxyls.



   Polycarbonates can, for example, be obtained from an aromatic diol and a bis-

 <Desc / Clms Page number 25>

 haloformate of a diol by the following reaction:
 EMI25.1
 In this reaction, x has a high value, while R and R 'denote the same or different organic groups, R' having an aromatic character. In this way, an organic compound having a reactive hydroxyl group and a reactive carbonic acid halide group (eg, a mono chloroformate of an organic diol) can be used as a source of the groups giving rise to the reaction. forming a series of carbonate bonds and hence a polycarbonate.



   It is also not essential that the organic compounds having the carbonic acid halide groups be preformed. In fact, these groups can also be formed in situ. Thus, organic diols, in particular bisphenols can, when they are phosgenated (that is to say when phosgene is passed through an alkaline aqueous solution of a bisphenol), give rise to the formation of polycarbonates. This can be regarded as a reaction of phosgene with alcoholic or phenolic hydroxyl groups, in the presence of an alkali, with as an intermediate stage the formation of carbonic acid chloride (chloroformate) groups of the bisphenols.



   In accordance with the present invention, in a preferred embodiment thereof, polycarbonates are prepared from a reaction medium formed of an organic diol, especially a bisphenol, an aqueous solution of an inorganic alkali. and a water-insoluble organic solvent, in which the polycarbonate is soluble, completing the formation of the polycarbonate in a

 <Desc / Clms Page number 26>

 emulsified reaction medium. Surprising results are obtained when the formation of the polycarbonate in the emulsion is completed. One of the most notable advantages is the surprising increase in the rate of formation of high molecular weight polycarbonates.

   The emulsion has the effect of greatly accelerating the formation of high molecular weight polycarbonates, reducing the reaction time to a minor fraction, i.e. to less than 1 / 5th of what would normally be. this reaction time.



   The emulsion or the emulsified reaction medium is a synthetic medium generated by altering the normal state of the reaction medium by various measures, some of which will be explained in more detail below.



  One of the dominant characteristics of the state which the reaction medium assumes when it is emulsified is the dispersion of a good fraction of its aqueous phase, usually at least 50% by weight or more, in the form of fine droplets in the water. the organic phase. No appreciable portion of the aqueous phase thus dispersed as a discontinuous phase in the continuous organic phase of the emulsion separates readily, when the emulsion is allowed to stand under quiet conditions, in less than an hour. Often it takes several hours and even days for the emulsion to break down on standing. Breaking up the emulsion may require positive measures, such as acidification, for example by adding hydrochloric acid.

   When the reaction mixture is emulsified, in accordance with preferred practices, as described below, the emulsion occupies a major part of the reaction medium. Thus, while prior to organic phase emulsification (if phase separation is permitted under conditions

 <Desc / Clms Page number 27>

 quiet) can occupy half the volume, the emulsion will occupy more than 75% and often 90% or more of the total volume of the reaction medium.



   The emulsified part of the reaction medium is a thick pasty mass which resembles whipped cream while, however, exhibiting a firmer texture.



  Usually, this paste is very sticky and adheres to a glass rod which is dipped in and removed from it.



   When phosgenating a reaction medium formed from bisphenol A, an aqueous solution of sodium hydroxide and methylene chloride, to obtain high molecular weight polycarbonates, reaction times of 10 hours to several days.



  Thus, while low molecular weight products are formed in shorter times, these extended times are necessary for obtaining polycarbonates having high molecular weights. When the formation of polycarbonates is completed in an emulsified reaction medium, a few hours, usually less than 3 hours, and often 1 to 2 hours, suffice.



   In practice, a reactor is charged with bisphenol A, an aqueous solution of sodium hydroxide and methylene chloride or a similar water-insoluble organic solvent. While stirring the reaction medium, phosgene is gradually added thereto, for example at a rate such that this addition takes 30 to 200 minutes. In this way, the reaction medium is charged with 1.0 to 1.3 moles of phosgene per mole of bisphenol A.



   As soon as it is formed, in the reactor and during the phosgenation, the reaction medium has a heterogeneous character]. The stirring serves to disperse the respective phases.

 <Desc / Clms Page number 28>

 tives and ensures this heterogeneous character. If moderate stirring is not carried out, the medium separates into a heavy organic phase consisting mainly of methylene chloride and polycarbonate, and into an aqueous phase containing the water-soluble constituents of the reaction medium, which constituents may include sodium hydroxide, sodium chloride and water soluble bisphenol A derivatives, such as bisphenol A phenates.



   During the addition of phosgene, a reaction or reactions apparently occur which lead to the formation of polycarbonates. However, high molecular weight polycarbonates are not immediately obtained. On the contrary, polycarbonates of low molecular weight apparently first form, even with continuous stirring of the reaction medium after the addition of phosgene, the chlorine content of chloroformate in the reaction medium remains for a long time. extended to a level which indicates that high molecular weight polycarbonates do not form rapidly.



   According to the discovery of the present invention, the formation of high molecular weight bisphenol A polycarbonates is catalyzed or accelerated, unexpectedly, by altering the physical character of the heterogeneous reaction mixture in the reactor, causing changing this mixture from a state in which phase separation is easily possible to that of an emulsion in which no phase separation occurs within a short period of time on standing. When the reaction medium is converted into an emulsion , the disappearance of the chloroformate chlorine from the reaction medium is greatly accelerated and high molecular weight bisphenol A polycarbonates are formed.

 <Desc / Clms Page number 29>

 



   In its normal state, the reaction mixture is heterogeneous during and after phosgenation, this mixture comprising an organic phase (consisting mainly of the solvent and the constituents soluble in it) and an aqueous phase (consisting mainly of water. and constituents soluble in water, such as caustic alkali, sodium chloride and water-soluble derivatives of bisphenol A, such as phenates of bisphenol A).



  On standing and without stirring, this reaction mixture rapidly (within a few minutes) breaks down into two distinctly distinct phases, the respective volumes of which correspond approximately to the volumes of water and water-insoluble organic solvent charged. in the reactor.



   Moreover, when this reaction medium is emulsified, it is converted into a thick pasty mass, which resembles whipped cream. The emulsion persists, as soon as it has formed, for a considerable time, that is to say for several hours and even for several days. It does not separate quickly into two large volume phases. On the contrary, the volume of the emulsion occupies the major part of the volume of the reaction medium. A small settleable aqueous phase can be present with the emulsion, but its volume is small compared to the quantity of liquids charged to the reactor.



  The emulsion occupies a much larger fraction of the total volume of the reaction mixture than the organic phase normally encountered. It is not extraordinary that by volume is between 1.5 and 5 times that of the normal organic phase which separates on standing.



   The organic constituents of the reaction mixture, primarily the organic solvent and constituents soluble therein, especially polycarbonate, form the continuous phase of the emulsion. In this continuous organic phase, are dispersed, with extr.

 <Desc / Clms Page number 30>

 ordinary, innumerable small spheres, which constitute the discontinuous phase and which consist of water and water soluble compounds. Microscopic examination of this emulsion, as it forms and initially exists in the reaction medium, shows that the small spheres are less than 5 microns, for example 0.5 to 5 microns, and predominantly there 2 microns in diameter.

   In general, these spheres are extraordinarily uniformly dispersed in the continuous phase and are typically very uniform in size.



   Various measures can be used to transform the heterogeneous unemulsified reaction medium into an emulsion. One of the most efficient techniques, which constitutes a preferred embodiment of the present invention, is to vigorously agitate a relatively small portion of the reaction medium, when at least part of the phosgenation has taken place, by vigorously agitation. stirring using a stirrer rotating at speeds of the order of several tens of thousands of revolutions per minute.



  When vigorous agitation of this nature is carried out, it is ordinarily found in less than a minute that the characteristics of the fraction are radically modified and that the desired emulsion is formed. By bringing this emulsified material into contact with the reaction medium, the entirety of this medium emulsifies, usually within a few minutes to 1 hour. Moderate agitation, such as that applied during phosgenation, facilitates this emulsification.
A suitable procedure is to prick and emulsify a small portion of the reaction medium.

   However, a small fraction can be emulsified by isolating and vigorously stirring in the reaction medium a small fraction thereof, for example by /

 <Desc / Clms Page number 31>

 insertion of an apparatus, which isolates and agitates the small fraction in the remainder of the reaction medium. The latter may optionally surround the fraction isolated and stirred by the apparatus in question. It is also possible to vigorously agitate a localized fraction of the reaction medium, to ensure proper emulsification.



   Moreover, the small amount of emulsified material need not necessarily be derived from the specific reaction medium which ultimately initiates emulsification. Thus, in batch operation, a small emulsified fraction of a preceding charge will serve to initiate the emulsification of a subsequent charge.



   Very small amounts of emulsified material will effectively initiate emulsification of the main reaction medium. Amounts of about 0.5% emulsified material per volume of reaction medium are sufficient. Of course, larger amounts of emulsified material can be emulsified. In general, the emulsified material is used in amounts between 1 and 5% by volume of the main medium.



   Other conditions should preferably be observed to facilitate the emulsification of the reaction medium, when the small emulsified fraction is incorporated therein. Thus, it is recommended not to stir the reaction medium during the addition of the emulsified fraction. Preferably, the reaction medium should be separated into its two main phases, as will occur if no agitation takes place (eg, organic phase and aqueous phase), when the emulsion is added.



   As soon as the emulsion is added, the medium is stirred moderately in the same way as during the phosgenation. Thus in many procedures the agitation ordinarily applied to form the reaction medium.

 <Desc / Clms Page number 32>

 nel main is interrupted, the emulsion is added and agitation is then resumed.



   On the other hand, it is also frequently preferable to add the emulsion to a main reaction medium which has been phosgenated to an extent of between 5 and 17%, preferably between 6 and 10% of stoichiometric excess of. phosgene. In other words, an amount of between 5 and 17 mol% of excess phosgene (based on the amount of phosgene needed to form the polycarbonate from the organic diol and alkali used) is added. to the reaction medium before the addition of the emulsion. However, it is possible to add the emulsion to a phosgenic medium to a greater or lesser degree.



   The following example illustrates the process for emulsifying the reaction medium and obtaining polycarbonates of high molecular weight.



   EXAMPLE VI.-
33.6 g (0.84 mol) of sodium hydroxide and 310 ml of water are charged in a three-necked flask with a capacity of one liter, equipped with a paddle stirrer.



  After dissolution of the hydroxide, 68.4 g (0.3 mol) of bisphenol A are added, which is allowed to dissolve. To the mixture obtained, 180 ml of methylene chloride are then added.



   While stirring the mixture using the stirrer rotating at 300 rpm, 33.6 g (0.34 mole) of phosgene are gradually added over the course of 50 minutes.



  The temperature of the mixture is maintained at 25 ° C. The chlorine content of the chloroformate is at this moment 6% relative to the weight of polycarbonate.



   A small fraction (50 ml) of the mixture presently in the vial is withdrawn from it and emulsified in a beaker, shaking vigorously, for 1

 <Desc / Clms Page number 33>

   timer using a Brookfield stirrer rotating at 10,000 revolutions per minute.



   The resulting emulsion is introduced into the flask with the agitator turned off, after which the agitator is started by rotating it at 300 revolutions per minute for two hours. At the end of this period, the chlorine content of chloroformate is 0.001% based on the weight of polycarbonate. The contents of the vial turn into an emulsion shortly after the addition of the emulsified fraction.



   This emulsion is then broken up by adding dilute hydrochloric acid, after 4uoi the organic phase is separated, washed until it is free of chloride ions, dried over anhydrous sodium sulfate and evaporated, so that one obtains a high molecular weight bisphenol A polycarbonate having a K value of 58.



   By way of comparison, it takes 10 to 24 hours of moderate stirring, in the absence of the emulsion, to reduce the chlorine content of chloroformate to 0.001% and to obtain a polycarbonate of molecular weight (value K) comparable.



   In the previous example, the molar ratio of sodium hydroxide and / or phosgene to bisphenol A employed was changed, using 2.8 to 3.5 moles of sodium hydroxide and 1.5 to 1.3 moles of phosgene per mole of bisphenol A with comparable results.



   It is also possible to use comparable mechanical agents to emulsify the reaction mixture or, preferably, a part of it.



   On a larger scale, the procedure of Example 6 was carried out as follows.



   EXAMPLE VII.-
A container with a capacity of 20 gallons, equipped

 <Desc / Clms Page number 34>

 with a jacket and a stirrer and kept under a nitrogen atmosphere was charged with 13.3 liters of water, 3.285 kg (42.2 moles) of a very pure aqueous solution of hydroxide of sodium containing 51.1% by weight of NaOH, 3.42 kg (15 moles) of bisphenol A and 9.0 liters of methylene chloride. Only half of the sodium hydroxide was added until all of the bisphenol A was dissolved and during this time no more methylene chloride was added.



   After cooling the contents of the vessel to 25 ° C. by circulating a liquid coolant through the jacket, 1.66 kg (16.77 moles) of phosgene gas was added at a substantially constant rate, in within 60 minutes, rotating the agitator at 120 revolutions per minute. A small sample (about 1 liter) of the reaction mixture was taken and emulsified by vigorous stirring, for about 1 minute, with a Bnookfield stirrer rotating at 10,000 rpm.



   This emulsified sample was returned to the vessel, the agitator of which had been turned off and the contents of which had separated into its two predominant phases.



  Emulsification of the reaction mixture then proceeded with resuming normal stirring for two hours.



  By this time, the formation of the polycarbonate was substantially complete, and all of the chlorine in the chloroformate had reacted.



   The emulsion was broken up and the mixture was made into a composition with easily separable phases, comprising an aqueous phase and an organic phase (mainly consisting of methylene chloride containing dissolved polycarbonate), by addition

 <Desc / Clms Page number 35>

 of 18 liters of methylene chloride. After separation of the phases, the organic phase was washed until it was free from chloride ions with water and the polycarbonate was isolated from methylene chloride by adding heptane, so as to precipitate granular polycarbonate.



   Rather than mechanically emulsifying part of the feed, from which the emulsification of the entire feed is then carried out, it is also possible, as indicated in the following example, to ensure emulsification by vigorous stirring of the entire mixture. reaction.



   EXAMPLE VIII.-
In a one liter flask, fitted with three tubes and equipped with a stirrer, 33.6 g (0.4 mole) of sodium hydroxide and 310 ml of water were charged. After dissolving the hydroxide 68.4 g (0.3 mole) of bisphenol A was added and dissolved. To this mixture was added 180 ml of methylene chloride.



   While rotating the stirrer at a speed of 300 revolutions per minute, 33.6 g (0.34 mole) of phosgene were added uniformly over the course of 50 minutes. The temperature of the mixture was maintained at 25 ° C. After the addition of the phosgene, the chlorine content in the chloroformate was 6% based on the weight of the polycarbonate.



   The resulting reaction mixture was transferred to a large capacity vessel, where it was vigorously stirred for one minute with a Brookfield stirrer rotating at 10,000 rpm.



  The resulting emulsion was stirred gently for two hours, after which it contained 0.001% by weight of chloroformate chloride, based on the polycarbonate.



   The polycarbonate recovered by the procedure of Example VI had a K value of 58.



   On a larger scale, the process of emulating

 <Desc / Clms Page number 36>

 Theification of Example VIII is best carried out by localized violent stirring. This consists, for example, in subjecting part of the interfacial region of the two phases of the reaction medium to violent stirring.



  Thus, violent agitation of the entire reaction medium is not essential. Emulsification of the reaction medium can take place before the completion of the phosgenation. Thus, although this is not advisable, part of the phosgenation or the addition of phosgene can take place in an emulsified reaction medium. When gaseous or liquid phosgene is added to the reaction mixture, the reaction medium can be emulsified even while the addition of phosgene is continuing. However, emulsification should not take place until at least one third of the total amount of phosgene has been added. The best emulsification and formation of polycarbonate occurs when emulsification occurs after the addition of phosgene.



   Other techniques for emulsifying the reaction medium can / be applied.



   One of these techniques, illustrated by Example IX, consists in carrying out the emulsification by controlling the way in which the sodium hydroxide or the analogous organic alkali is incorporated into the reaction medium. Thus, during a batch phosgenation, only half of the total amount of NaOH required (1.2 to 1.4 moles of NaOH per mole of bisphenol A) is initially charged into the reactor and the phosgenation is initiated. When the addition of 30 to 85% of the phosgene (about 0.3 to 0.9 moles of phosgene per mole of bisphenol A) is complete, the remainder of the sodium hydroxide is added. During this reaction, or a few minutes after this reaction, the reaction medium undergoes, surprisingly, an emulation.

 <Desc / Clms Page number 37>

 -sification. The addition of phosgene is then completed.



   EXAMPLE IX.-
68.4 g (0.3 mol) of bisphenol A, 188 ml of methylene chloride, 100 ml were introduced into a flask with a capacity of one liter, with three tubes, equipped with a paddle stirrer. of water and 105 ml of 4N aqueous sodium hydroxide solution. The flask was immersed in an ice bath and, during the reaction, the temperature was then kept at 25 ° C.



   While rotating the agitator at 300 rpm, a total of 33 g (0.33 moles) of phosgene gas was added to the liquid mixture over 50 minutes at a uniform rate, if this. was only halfway through the addition of phosgene, the latter was stopped for 3 to 5 minutes, to add 105 ml of 4N aqueous sodium hydroxide solution. During this exposure and after the addition of sodium hydroxide, the reaction mixture emulsified.



   After stirring the reaction mixture for 2 hours after the addition of phosgene was completed, the polycarbonate no longer contained detectable chloroformate chloride. The polycarbonate recovered by the process of Example VI had a K value of 53.



   By repeating the procedure of Example IX, but adding a second charge of sodium hydroxide when 30, 40, 60.70 and 80% of the total amount of phosgene had been added, comparable results were obtained, with emulsification and rapid production of a high molecular weight polycarbonate.



   The following example shows how the invention can be implemented in the manner described in Example IX, on a larger scale.

 <Desc / Clms Page number 38>

 



   EXAMPLE X.-
A 20 gallon capacity vessel, fitted with a jacket and stirrer, was charged with 26.4 liters of water, 6.84 kg (30.0 moles) of bisphenol A and 3 , 3 kg (42.0 moles) of an aqueous solution of sodium hydroxide containing 50.97% by weight of NaOH. A nitrogen atmosphere was maintained in the vessel. After complete dissolution of the bisphenol A, the reaction mixture was cooled to 25 ° C. by circulating a cooling agent through the jacket. Then 18 liters of methylene chloride were added.



   While maintaining the temperature at 25 ° C and operating the stirrer at ¯120 rpm, 1.671 kg (17.0 moles) of phosgene gas were added at a substantially constant rate over the course of 36 minutes. - your. The addition of phosgene was then stopped for 10 minutes, during which 3.4 kg (42.0 moles) of aqueous sodium hydroxide containing 50.91% by weight NaOH was added rapidly, taking care to maintain the temperature at 25 ° C. During this addition of sodium hydroxide, the mixture emulsified. The addition of phosgene was then resumed and 1.699 kg (17.0 moles) of phosgene was further added over 50 minutes at a substantially constant rate.



   After the addition of phosgene, the stirrer was restarted and temperature control resumed as during phosgenation, for 2 hours. During this time all of the chloroformate chloride was gone and the formation of polycarbonate continued and completed. The emulsion was then broken up by adding 36 hours of methylene chloride. After separation of the organic phase - and washing of the latter with water - until it is free of chloride ions, the polycarbona

 <Desc / Clms Page number 39>

 It was precipitated as a granular product by adding heptane to the methylene chloride solution.



   Still other means can be used to emulsify the reaction mixture and thereby accelerate the formation of high molecular weight polycarbonates.



  The following example illustrates one of these ways.



   EXAMPLE XI. -
In a one liter capacity flask with five tubes, 68.4 g (0.3 mole) of bisphenol A, 188 ml of methylene chloride and 100 ml of water were charged. A Beeman Zéromatiq ph meter with a tubular type reference electrode and a standard glass electrode was immersed in the contents of the vial to allow the pH to be measured. Other tubing from the vial was used to introduce gaseous phosgene and sodium hydroxide, as well as for the insertion of a thermometer and a stirrer.



   The pH of the reaction mixture was then adjusted to 11 by addition of 7 ml of a 4N aqueous solution of sodium hydroxide. While the flask was immersed in an ice bath and maintained at 25 ° C and while the stirrer was operated to moderate the contents of the flask, 33.6 g (0.34 mole) of phosgene gas was introduced into the flask. the liquid medium over 50 minutes at a rate of 0.66 g per minute. A 4N aqueous sodium hydroxide solution is then added in an amount necessary to maintain the pH of the reaction mixture at a value between 10, 8 and 11 during the first 33 minutes of the addition of phosgene.

   At this time, 50 ml of the 4N sodium hydroxide solution was charged to the vessel to cause the reaction medium to emulsify.

 <Desc / Clms Page number 40>

 



   After the end of the addition of phosgene, while slowly adding the remainder of the sodium hydroxide so that the end of this addition coincides with the end of the addition of phosgene (a total of 210 ml of 4N solution of (sodium hydroxide), stirring was continued for 3 hours, whereby a high molecular weight polycarbonate was obtained. This was recovered as described in detail in Example VI. This polycarbonate had a K value of 53 and a chlorine content of chloroformate of 0.001% based on the weight of the polycarbonate.



   The K values shown herein were obtained by weighing 0.2500g of the polycarbonate into a 50ml capacity flask and then adding 25ml of dioxane. Moderate heating in a steam bath with some agitation is used to achieve complete dissolution. After cooling to 25 ° C. and adding a sufficient quantity of dioxane to bring the level up to the calibration line carried by the volumetric flask, the solution is mixed well and filtered through a sintered glass filter, applying a minimum of vacuum . The viscosity of the filtrate is determined by transferring 10 ml fractions of the solution to a modified Ostwald viscometer, placed in a constant temperature bath of 25 ° C. for 5 minutes. The flux time at 25 C is determined.

   The dioxane is filtered and its efflux time is determined in the same way. Relative viscosity is the ratio of the flow time of the solution to the flow time of the solvent. The logarithm of the relative viscosity is determined and the K value to which it corresponds is formed by reference to a graph indicating the relationship between known K values and known relative viscosities.

 <Desc / Clms Page number 41>

 



   Considerable latitude is allowed under the other conditions of the reaction. Temperatures above the freezing point of the reaction mixture and below the boiling point of the organic solvent are suitable. Suitable reaction temperatures are between 0 C and 40 C. Somewhat higher temperatures, for example above the normal boiling point of the solvent (or above those at which substantial volatilization of the solvent occurs) , can be used if sealed reactors (autogenous pressure) or if pressures above atmospheric pressure are applied. The operation is currently carried out at atmospheric pressure.



   The total amount of sodium hydroxide or the like alkali mineral used for a given polycarbonate formation usually exceeds the stoichiometric amount. In the phosgenation of bisphenol A, for example, 2.5 to 4.0 moles of NaOH are used per mole of bisphenol A.



   Complete conversion of bisphenol A is preferred. Consequently, the other reagents, namely phosge and inorganic alkali, are used in quantities capable of directly providing a polycarbonate containing a minimum of bisphenol A or not containing it. However, it is not essential for obtaining high molecular weight products to convert all of the bisphenol A.



   The ratio of water to organic solvent in the reaction medium facilitates the formation of an emulsion, The relative volumes, which make the reaction mixture most suitable for emulsification, are of the order of 0.3 to 1.5 volume of organic solvent per mole of water.



  Each of the particular organic solvents will exhibit, within this range of values, a particular optimum value.

 <Desc / Clms Page number 42>

 re. With methylene chloride, the preferred value is about 0.5 to 0.8 volume of solvent per volume of water.



   Another factor which contributes to the emulsification of the reaction medium is the polycarbonate concentration.



  When the polycarbonate content is between 12 and 30% by weight of the organic solvent, emulsification takes place a little more easily than with more dilute polycarbonate solutions. Thus, it is preferable to use bisphenol A in an amount corresponding to about 10-30% by weight of the organic solvent.

 <Desc / Clms Page number 43>

 



   Although the invention has been described with reference to specific details of certain embodiments, it is understood that it should not be considered as limited to these details, many modifications being possible without departing from the scope of the invention. as defined in the following claims.



    CLAIMS.-
1.- Process for the preparation of high molecular weight aromatic polycarbonate, characterized in that a liquid reaction medium containing the monophenate of an aromatic diol or a source of such a monophenate is subjected to phosgenation.



   2. - A process for the preparation of high molecular weight aromatic polycarbonate by reacting in a liquid reaction medium a series of carbonic acid halide groups and a series of hydroxyl groups, at least part of which are phenolic hydroxyl groups of an aromatic diol, characterized in that monophenate of the aromatic diol is used in the reaction medium.



   3. - Process for the preparation of an aromatic polycarbonate of high molecular weight, characterized in that a liquid medium consisting of an aromatic diol and an alkali metal hydroxide is subjected to phosgenation and is limited, for a part substantial portion of the phosgenation period, the amount of alkali metal hydroxide to less than two moles of alkali metal hydroxide per mole of aromatic diol.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

4.- Process for the preparation of high molecular weight aromatic polycarbonate by reacting in a liquid medium a series of carbonic acid halide groups and a series of hydroxyl groups comprising the phenolic hydroxyl groups of a diol. aromatic, characterized in that a substantial part of the <Desc / Clms Page number 44> reacting in a liquid medium formed of an aromatic diol and an alkali metal hydroxide in the molar proportion of less than two moles of alkali metal hydroxide per mole of aromatic diol. 5. - Process according to claim 4, characterized in that the molar ratio is 0.1 to 1.8 moles of alkali metal hydroxide per mole of aromatic diol. 6. - Process for the preparation of aromatic polycarbonate of high molecular weight, characterized in that an aqueous liquid medium formed of an alkylidene bisphenol and an alkali metal hydroxide is subjected to phosgenation, the ratio of the alkali metal hydroxide of alkylidene bisphenol being less than 2.1, during a substantial part of the period of phosgenation. 7.- A process for the preparation of high molecular weight aromatic polycarbonate, characterized in that an aqueous liquid medium of an aromatic diol and an alkali metal hydroxide is subjected to phosgenation and the aqueous medium is maintained at a pH of about 10.8 to 11 a substantial part of the during a / period of phosgenation. 8. A process for the preparation of high molecular weight aromatic polycarbonate, characterized in that a liquid medium containing the monophenate of an aromatic diol and the diphenate of an aromatic diol is subjected to phosgneation. 9. - Process for the preparation of aromatic polycarbonate of high molecular weight, characterized in that a phosgenation is applied to an aqueous liquid medium formed of an aromatic diol and an alkali metal hydroxide in a molar ratio of more one mole and not more than 1.5 moles of alkali metal hydroxide per mole of aromatic diol. <Desc / Clms Page number 45> 10. - Process for the preparation of high molecular weight aromatic polycarbonate, characterized in that a liquid medium formed of an aromatic diol and an alkali metal hydroxide is subjected to phosgenation and an appreciable chlorine content of chloroformate, up to about 2% by weight of the organic constituents of the liquid medium, substantially throughout the duration of the phosgenation. 11.- Process for the preparation of high molecular weight aromatic polycarbonate, characterized in that a liquid medium consisting of an alkylidene bisphenol and an alkali metal hydroxide, water and an insoluble organic solvent is subjected to phosgenation. in water for the polycarbonate, while maintaining an appreciable chlorine content of chloroformate in the reaction mixture up to about 2% by weight of chlorine chloroformate based on the weight of the organic phase, substantially throughout the entire time phosgenation. 12. - Process for the preparation of high molecular weight aromatic polycarbonate, characterized in that phosgene is initially added to a liquid medium consisting of an aromatic diol and an alkali, the quantity of alkali n being only a fraction of that stoichiometrically required for the formation of the diol diphenate, and alkali is added to the reaction mixture before the addition of phosgene is complete. 13. - Process for the preparation of high molecular weight aromatic polycarbonate by phosgenation of an aromatic diol, characterized in that phosgene is added to a liquid medium consisting of an aromatic diol and of - a metal hydroxide. alkaline, the quantity of alkali metal hydroxide contained in the <Desc / Clms Page number 46> a liquid to which phosgene is added initially at a fraction of the amount sooichiometrically required to form the diphenate of the aromatic diol, and an additional amount of alkali metal hydroxide is added before the addition of the phosgene is complete. 14.- Process for the preparation of high molecular weight aromatic polycarbonate by phosgenation of an alkylidene bisphenol, characterized in that phosgene is added to a liquid medium consisting of bisphenol and an alkali metal hydroxide, the amount of d is limited. alkali metal hydroxide to less than that stoichiometrically required to form bisphenol diphenate in the liquid medium at the start of the addition of phosgene, and alkali metal hydroxide is added to the medium before completion of the addition. addition of phosgene. 15. - A process for the phosgenation of bisphenol A to obtain polycarbonate of high molecular weight, characterized in that phosgene is added to a liquid medium of bisphenol A and an alkali metal hydroxide, the quantity of d is limited. alkali metal hydroxide to less than that stoichiometrically required to form bisphenol A di-phenate in the medium at the start of the addition of phosgene, and an additional amount of alkali metal hydroxide is added to the medium before adding complete the addition of phosgene. 16. - Process for the preparation of polycarbonate, characterized in that phosgene is passed through a reaction mixture of alkylidene bisphenol, of an aqueous solution of hydroxide of an alkali metal and of a solvent. The organism of the water-insoluble polycarbonate, the passage of phosgene and the formation of low molecular weight polycarbonate are completed, a small amount of the emulsified reaction mixture is introduced into the medium. <Desc / Clms Page number 47> phosgene and the phosgene medium is thus emulsified, and high molecular weight polycarbonate is formed in the emulsified medium. 17.- Process for preparing polycarbonate by passing phosgene through a reaction medium of bisphenol A, an aqueous solution of alkali metal hydroxide and a solvent / organic for the water-insoluble polycarbonate, characterized in that when the passage of phosgen and the formation of a low molecular weight polycarbonate is completed, a small amount of the emulsified reaction mixture medium is brought into the phosgene medium and thus the phosgene medium is emulsified, and formed in the emulsified medium of high molecular weight polycarbonate. 18.- Process for the preparation of polycarbonate by passing phosgene through a reaction mixture of bis-phenol A, an aqueous solution of alkali metal hydroxide and a partially halogenated aliphatic hydrocarbon insoluble in water. water, this hydrocarbon serving as a solvent for the polycarbonate, characterized in that the passage of phosgene and the formation of a polycarbonate of low molecular weight are completed, a small quantity of emulsified reaction mixture medium is brought into the medium phosgene and thus the phosgene medium is emulsified, and high molecular weight polycarbonate is formed in the emulsified medium. 19. - Process for preparing polycarbonate by passing phosgene through a heterogeneous reaction mixture of alkylidene bisphenol, aqueous alkali metal hydroxide and an organic solvent insoluble in water for the polycarbonate, characterized in. in that the passage of phosgene is completed and a low molecular weight polycarbonate having an appreciable content is formed <Desc / Clms Page number 48> in chlorine of chloroformate, one emulsifies a heterogeneous medium of polycarbonate of low molecular weight, of water and of an organic solvent of the insoluble polycarbonate in water, the emulsified medium is incorporated into the reaction mixture so as to emulsify the latter and to form high molecular weight polycarbonate with a low chlorine content of chloroformate in the emulsified mixture. 20. - A process for preparing polycarbonate by passing phosgene through a heterogeneous reaction mixture of bisphenol A, aqueous alkali metal hydroxide and an organic solvent for the polycarbonate insoluble in water, characterized in that the process is completed. passage of phos- gen and forming a low molecular weight polycarbonate having an appreciable content of chloroformate chloride, emulsifying a homogeneous medium of low molecular weight polycarbonate, water and organic solvent of the insoluble polycarbonate. water, and the emulsified medium is incorporated into the reaction mixture, so as to emulsify this mixture and to form a high molecular weight polycarbonate with a lower chlorine content of chloroformate in the emulsified mixture. 21. - Process for the preparation of polycarbonate by passing phosgene through a heterogeneous reaction mixture of bisphenol A, aqueous alkali metal hydroxide and a partially halogenated and water-insoluble hydrocarbon serving as a solvent for the polycarbonate, characterized in. In that the passage of phosgene is completed and a low molecular weight polycarbonate having an appreciable chloroformate content is formed, a heterogeneous medium of low molecular weight polycarbonate, water and a mixture is emulsified. partially halogenated hydrocarbon, insoluble in water and serving as a solvent for the polycarbonate, the emulsified medium is incorporated into the <Desc / Clms Page number 49> reaction mixture, so as to emulsify this reaction mixture and form high molecular weight polycarbonate with lower chlorine content of chloroformate in the emulsified mixture. 22. - A process for preparing polycarbonate by passing phosgene through a heterogeneous reaction mixture of alkylidene bisphenol, aqueous alkali metal hydroxide and an organic solvent for the polycarbonate insoluble in water, characterized in that one completes passage of phosgene and forming a low molecular weight polycarbonate having an appreciable chlorine content of chloroformate, vigorously agitating and emulsifying a small fraction of the phosgene medium, and emulsifying the whole of the phosgene medium with the aid of the small fraction emulsified and high molecular weight polycarbonate is formed in the emulsified medium. 23. - Process for the preparation of polycarbonate by passing phosgene through a heterogeneous reaction mixture of alkylidene bisphenol, alkali metal hydroxide aquex and an organic solvent insoluble in water for the polycarbonate, characterized in after completing the passage of phosgene and forming a low molecular weight polycarbonate having an appreciable chlorine content of chloroformate, a small fraction of the phosgene medium is isolated, the small fraction is emulsified by vigorous stirring, the mixture is emulsified. phosgenic medium by incorporating the emulsified fraction therein, and the low molecular weight polycarbonate is converted to. Higher molecular weight polycarbonate with low chlorine content of chloroformate. 24; 0 Process for the preparation of polycarbonate by passing phosgene through a hetero reaction mixture. <Desc / Clms Page number 50> Rogen of alkylidene bisphenol, aqueous alkali metal hydroxide and an organic solvent of the water-insoluble polycarbonate, characterized in that the passage of phosgene is terminated and a low molecular weight polycarbonate having an appreciable content is formed in chloroformate, a small fraction isolated from the phosgene medium is emulsified, the reaction mixture is allowed to separate into its two main immiscible phases, the emulsified fraction is added to the mixture while its phases are thus separated, the resulting medium is stirred to emulsify and the low molecular weight polycarbonate is converted to higher molecular weight low chlorine chloroformate polycarbonate. 25.- Process for the preparation of polycarbonate by passing phosgene through a heterogeneous reaction mixture of bisphenol A, aqueous alkali metal hydroxide and partially chlorinated hydrocarbon, insoluble in water, serving as solvent for the preparation. polycarbonate, characterized in that the passage of phosgene is completed and low molecular weight polycarbonate having an appreciable content of chloroformate chloride is formed, a small isolated fraction of the phosgene medium is emulsified, the reaction mixture is allowed to separate into its two main immiscible phases, the emulsified fraction is added to the mixture while its phases are thus separated, the resulting medium is stirred so as to emulsify the medium and the low molecular weight polycarbonate is converted to higher molecular weight low chlorine polycarbonate of chloroformia. 26. A process according to claim 25, charac- terized in that during emulsification the phase <Desc / Clms Page number 51> The continuous emulsified reaction medium consists of the partially chlorinated hydrocarbon, while the discontinuous phase consists of the aqueous component in the form of small spheres with a diameter of less than 5 microns. 27. - Process for preparing polycarbonate, in substance, as described above.