DE1173250B - Process for the production of pure, grainy polycarbonates with a high bulk weight - Google Patents

Description

Process for the production of pure, granular polycarbonates of high bulk density The invention relates to a process for the production of pure granular polycarbonates high bulk density from solutions of alkylidenebisphenol polycarbonates in part halogenated aliphatic hydrocarbons having 1 to 4 carbon atoms, where the polycarbonate solutions with a monohydric alcohol up to the cloud point diluted, let the diluted solutions stand for 5 to 60 minutes and then continue precipitates with monohydric alcohol.

Alkylidenebisphenol polycarbonates, e.g. B. bisphenol A (p, p'-isopropylidenediphenol) polycarbonates, can, for example, by treatment of an aqueous sodium hydroxide solution Bisphenol A can be produced with phosgene, the polycarbonates during their Formed from the powder in the form of low bulk density and low purity precipitate aqueous solution.

Often, however, the addition of a water-insoluble, organic one Solvent, such as normally liquid, partially halogenated (especially chlorinated) hydrocarbons, of particular advantage for the reaction medium. In In these cases, the polycarbonate is obtained in the form of a solution.

For many purposes, e.g. B. as molding compounds, the alkylidenebisphenol polycarbonates used in the form of granular solids.

The transport and storage of solutions is complex, especially since the solvent often means waste for the consumer of the polycarbonate.

Granular solids are better for storage and handling as solutions, since paper bags or cardboard boxes can be used for solids, while metal drums are required for solutions. The separation of granular alkylidenebisphenol polycarbonates from the organic solvents is therefore advantageous.

In addition, it is very desirable to have pure granular polycarbonates high bulk density. The formation of lighter flaky polycarbonates is to avoid, because small amounts trapped or otherwise in the Polycarbonates of solvents present are disadvantageous.

If you evaporate the solvent of such solutions or with If water vapor drives off, a hard or tough elastic mass remains behind Purity harder to handle than granular alkylidene bisphenol polycarbonates.

There are already other polycarbonates made from ethers, such as dihydroxydiphenyl ether, and phosgene in solution of pyridine had been prepared from these solutions precipitated by dilution with n-hexane. The polycarbonate obtained was none pure granular solid with a high bulk density.

According to the invention, alkylidenebisphenol polycarbonates are in the form of pure granular solids of high bulk density, often in the range between 220 and 400 kg / m3 and more, which are almost free of entrapped organic Solvents are.

According to the invention, the solution of the alkylidenebisphenol polycarbonate in the partially halogenated aliphatic hydrocarbon having 1 to 4 carbon atoms first carefully diluted to the cloud point with monohydric alcohol, whereby the formation of a separate one, by the appearance of a mist in the liquid recognizable solid phase begins.

When the mixture has reached the cloud point, it is left to 5 to 60 minutes, preferably 5 to 20 minutes, and stir gently.

During this time, some of the polycarbonate may turn out to be a solid cut off or fail.

Then the solution obtained (with or without precipitate) further diluted with the monohydric alcohol, and further polycarbonate precipitates.

So much monohydric alcohol is used that either all of it alkylidene bisphenol polycarbonate in solution, or usually at least 50% of the dissolved polycarbonate precipitate. This precipitate is then mechanically, z. B. separated by filtration, centrifugation or decanting.

According to the process of the invention, a precipitate is obtained that of fine-grained particles of unusually uniform size and easy to separate from the liquid by mechanical devices is.

It is advantageous to use alkylidenebisphenol polycarbonate solutions, which contain 1 to 6 percent by weight and more than 15 percent by weight polycarbonate.

The process of the invention can be carried out at temperatures between 0 and 50 "C to be carried out.

Besides methanol, the other, normally liquid monohydric alcohols, Ethanol, n-propanol, isopropanol, allyl alcohol, n-butanol, isobutanol, secondary butanol, n-amyl alcohol, isoamyl alcohol, n-hexyl alcohol and mixtures thereof can be used. The monohydric alcohols used may be the alkylidenebisphenol polycarbonate does not dissolve and dissolve with the polycarbonate solution, at least to the extent that it does Do not mix them when used in the precipitation.

The total amount of alcohol required to precipitate almost all of the polycarbonate is about half the volume of the polycarbonate solution. In general is the cloud point of the polycarbonate solution is reached when the solution is treated with an amount of alcohol which makes up about half of its own volume (40 to 60 percent by volume), diluted became.

Solutions of alkylidene bisphenol polycarbonates are according to the invention in partially halogenated (especially chlorinated) aliphatic hydrocarbons having 1 to 4 carbon atoms, e.g. B. chloroform, methyl chloride, ethylene chloride, Acetylene dichloride, dichloroethylene, partially chlorinated propane and butane and in particular Methylene chloride, is used.

Furthermore, alkylidenebisphenol polycarbonate solutions are used, the z. B. derived from the following Alkylidenbisphenolen: (4,4'-Dioxy-diphenyl) -methane, Methylene-bis- (4-methyl-6-tert-butyl-phenol), methylene-bis- (4 <thyl-6-tert-butyl-phenol), 4,4'-butylidene-bis (3-methyl-6-tert-butyl-phenol), 2,2- (2,2'-dioxy-4,4'-di-tert-butyl-diphenyl) -propane , 2,2- (4,4'-Dioxy-diphenyl) -butane, 2,2- (4,4'-Dioxy-diphenyl) -pentane, 3,3- (4,4'-Dioxy-diphenyl) -pentane , 2,2- (4,4'-Dioxy-diphenyl) -3-methyl-butane, 2,2- (4,4'-Dioxy-diphenyl) -hexane, 2,2- (4,4'-dioxy- diphenyl) -4-methyl-pentane, 2,2- (4,4'-dioxy-diphenyl) -heptane, 4,4- (4,4'-dioxy-diphenyl) -heptane, 2,2- (4,4'-dioxy-diphenyl) -tridecane , 2,2-bis- (3,5-dichloro-4-oxypheny]) propane, 2,2-bis (tetrachloro-oxyphenyl) propane, 2,2-bis (3-chloro-4-oxyphenyl) propane.

Solutions of alkylidene bisphenol polycarbonates can also be used that are derived from two or more alkylidenebisphenols or from a mixture derived from Alkylidenbisphenolell and aliphatic diols.

The methylene chloride solutions of bisphenol polycarbonate used according to the invention were made according to the following known procedure: In an 11 capacity glass three-necked flask, 0.3 mol of bisphenol A, 0.84 mol of sodium hydroxide, 310 cc of water and 180 cc of methylene chloride were added and the mixture was then mixed with gentle stirring and at a temperature that was kept at about 25 "C, gaseous phosgene gradually passed in until 0.34 mol had been added.

After the phosgene addition was complete, the reaction mixture became stirred for a further 2 hours. The resulting reaction mixture separated into two Phases. The heavier phase, i.e. H. the methylene chloride solution of the polycarbonate, was separated and washed free of chloride ions with water. Example The polycarbonate solutions were used to maintain the polycarbonate concentrations recorded in the table required amounts of methylene chloride diluted. 200 cc proportions of these solutions were made at about 25 "C with gentle stirring gradually with methanol up to the cloud point offset. The dilution with methanol was then discontinued, but it became more Stirred for 60 minutes. Then the remaining methanol was added.

The precipitated polycarbonate was then filtered off and heated dried at 110C in an oven. A finely divided, unusual one was obtained uniform and granular high density polycarbonate that is essentially solvent free was.

The table shows the corresponding test conditions and results. Polycarbonate amount of added Concentration of methanol (cma) density of Poly- search in the solution up to the carbonate Weight residual turbidity (kg / m3) percentage point l 5.7 60.3 1 40 193.8 2 9.8 56.5 43.5 443.8 3 17.3 43.0 1 57 365.3 After precipitation, the precipitate in experiment 2 had a less good granular shape than in experiments 1 and 3.

Claims (2)

Claims: 1. Process for the production of pure granular polycarbonates high bulk density from solutions of alkylidenebisphenol polycarbonates in part halogenated aliphatic hydrocarbons having 1 to 4 carbon atoms, d a - characterized in that the polycarbonate solutions with a monovalent Alcohol diluted to the cloud point, the diluted solutions 5 to 60 minutes lets stand and then continues to precipitate with monohydric alcohol. 2. The method according to claim 1, characterized in that as monohydric alcohol methanol is used. Considered publications: German Auslegeschrift F 13040 IVd139c (announced June 21, 1956); announced documents of the Belgian Patent 559 191.