GB2099006A

GB2099006A - Manufacturing of aromatic polysulphones and polyketones

Info

Publication number: GB2099006A
Application number: GB8212422A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1981-05-26
Filing date: 1982-04-29
Publication date: 1982-12-01
Also published as: GB2099006B

Abstract

Manufacture of an aromatic polysulphone or polyketone by producing the polymer as a solution or dispersion in trifluoromethane sulphonic acid using the sulphonic acid as a reaction solvent or dispersant and as a polymerisation catalyst, providing for phosphoric acid (preferably H3PO4) to be present in said solution or dispersion, e.g. by adding it (or reactants which form it) to the solution or dispersion and/or by forming it during polymerisation, removing trifluoromethane sulphonic acid by distillation from the solution or dispersion so as to leave a solution of the polymer in the phosphoric acid and recovering the distilled trifluoromethane sulphonic acid, and isolating the polymer from its solution in phosphoric acid.

Description

SPECIFICATION Manufacture of aromatic polysulphones and polyketones The present invention relates to a process for the manufacture of aromatic polysulphones and polyketones.

It has been found that certain aromatic polysulphones and polyketones may be produced by electrophilic processes in which trifluoromethane sulphuric acid is used as a reaction solvent or dispersant and as a polymerisation catalyst.

One example of such processes is that for the manufacture of an aromatic polysulphone which comprises reacting under substantially anhydrous conditions at least one compound of formula

wherein -Y- is a direct link, -0-, -Ph-O- (where -Ph- is p-phenylene) -CF2-, -CR1 R2 where R1 and R2 which may be the same or different are each a fully fluorinated alkyl radical, or

where -X- and -X'- which may be the same or different are each a direct link, -0--CF2-, or-CR1R2 where R1 and R2 are as defined above, and Z is-CO-, SO2, -CF2- or-CR1R2- where R1 and R2 are as defined above, with a sulphonating agent and trifluoromethane sulphonic acid.

The trifluoromethane sulphonic acid acts as a polymerisation catalyst and is normally used in a large excess that it also serves as a reaction solvent or dispersant. The preferred sulphonating acid is concentrated sulphuric acid. Such a process has the advantage that it does not employ aromatic sulphonyl mono- or di-halides (which may be expensive or difficult to obtain) which have previously been used in electrophilic reactions for the manufacture of aromatic polysulphones.

A typical example of this reaction is that employing diphenyl ether, trifluoromethane sulphuric acid and concentrated sulphuric and which can be controlled to yield an aromatic polysulphone having predominantly "all-para" repeats units of formula

Another example of such processes is that for the manufacture of an aromatic polyketone which comprises polymerising at least one aromatic acyl halide of formula

where W is halogen, preferably F or Cl, and -0- is a direct link, --00-, --SS-, or

where p is 1 or 2, q is 1 or 2, r is O or 1, -G- is a direct link, -0-, or-S-, -G'- is a direct link, -0-, -S-, -CO-, SO2, or -C(CF3)2-, and -Q- is -CO-, SO2, or -C(CF3)2-, in the presence of trifluoromethane sulphuric acid. Again the trifluoromethane sulphonic acid acts as a polymerisation catalyst and is normally used in excess so that it also serves as a reaction solvent or dispersant. Such a process has the advantage that it avoids the use of the highly corrosive and physiologically harmful liquid HF/BF3 system previously employed in the commercial production of aromatic polyketones by an electrophilic process.

A typical example of this reaction is that employing 4-phenoxy benzoyl chloride which yields an aromatic polyketone having the repeat units of formula

While the use of trifluoromethane sulphuric acid in such processes is clearly potentially very attractive, it has to be said that this substance is expensive. Consequently for such processes to be viable as commercial operations, it is desirable for the trifluoromethane sulphuric acid to be easily and cheaply recoverable so that it can be recycled.

I have now discovered a process whereby trifluoromethane sulphonic acid may be readily and cheaply recovered from such processes so that it is available for re-use in the polymerisation reaction.

According to the present invention there is provided a process for the manufacture of an aromatic polysulphone or polyketone which comprises producing the aromatic polysulphone or polyketone as a solution or dispersion in trifluoromethane sulphuric acid using said sulphonic acid as a reaction solvent or dispersant and has a polymerisation catalyst, providing for phosphoric acid to be present in said solution or dispersion, removing trifluoromethane sulphuric acid by distillation from the solution or dispersion so as to leave a solution of the polymer in the phosphoric acid and recovering the distilled trifluoromethane sulphuric acid, and isolating the polymer from its solution in phosphoric acid.

The process of the present invention is effective because the aromatic polysulphone or polyketone is readily soluble in phosphoric acid. Consequently trifluoromethane sulphonic acid may be distilled off from the reaction medium (e.g. under reduced pressure) so as to leave a stable solution of the polysulphone or polyketone in phosphoric acid (which will of course probably contain a little residual trifluoromethane sulphuric acid), from which the polymer may be readily isolated-e.g. by pouring the solution into water or aqueous alkali whereupon the polymer precipitates as a solid which may be appropriately washed and dried. The recovered trifluoromethane sulphuric acid can then be recycled.

The phosphoric acid can be any one or more of the commonly available phosphoric acids, e.g.

orthophosphoric acid (H3PO4), pyrophosphoric acid (H4P2O7) metaphosphoric acid (HPO3) or hypophosphoric acid (H4P2O6). Of these, orthophosphoric acid (H3PO4) is preferred.

The presence of the phosphoric acid in the solution or dispersion of the polysulphone or polyketone in trifluoromethane sulphuric acid may, e.g., be provided for by adding the acid directly to the solution or dispersion, or by adding reactants to the solution or dispersion which form the acid-for example P2O5IH2O in the case of orthophosphoric acid.

Alternatively, at least some of the phosphoric acid may be present as a result of being formed during the polymerisation reaction. For example, in the reaction for the manufacture of an aromatic polysulphone employing a sulphonating agent (such as concentrated sulphuric acid) and trifluoromethane sulphuric acid described above, it may be beneficial to add P2O5, acting as a dehydrating agent, before and/or during the reaction as this can often increase the molecular weight of the resulting polymer. Consequently orthophosphoric acid (H3PO4) will automatically be present in the solution or dispersion of the polymer in trifluoromethane sulphonic acid as a result of being formed (from P205 and water) during the polymerisation reaction. Optionally, further phosphoric acid (or the reactants therefor) may be added.

The present invention is now illustrated by the following example.

Example Diphenyl ether (34.0 g, 0.2 mole) was weighed into a 3-necked flask (capacity 250 ml) fitted with a stirrer, internal thermometer and reflux condenser (protected with a drying tube), under a nitrogen blanket. 150 ml of trifluoromethane sulphuric acid were added and the mixture cooled to -250C with solid carbon dioxide. A solution of analar 98% w/w sulphuric acid (20.0 g, 0.2 mole) in 100 ml trifluoromethane sulphuric acid was added dropwise from the tap funnel into the stirred solution (the total amount of trifluoromethane sulphuric acid added therefore being about 250 ml). The mixture was stirred for 1 hour 20 minutes without heat being applied by which time its temperature had risen to 8bC and its colour had become deep red.The tap funnel was removed and 12.5 g (0.087 mole) P205 powder added (using a powder dispenser) through the free neck of the flask. The stirred mixture was heated to 800C (using an oil bath) and maintained substantially at this temperature for 26.5 hours.

Samples of about 1 7 g of the mixture were periodically removed with a clean syringe, each solution being injected into water to yield a white lace-like precipitate which was filtered off. Each precipitate was washed with water and methanol and dried in a vacuum oven. Nmr spectroscopy (200 M Hz) showed each precipitated solid to be an aromatic polysulphone consisting predominantly of the repeat units having the formula

The results of the sampling were as follows: : Time of sampling Weight ofsample RV of resulting polymer 2 hours 17.0 g 0.14 3 hours 1 7.2 g 0.22 4 hours 17.8 g 0.19 5 hours 17.0 g 0.24 6 hours 1 6.8 g 0.27 7 hours 1 6.9 g 0.35 8 hours 17.1 g 0.36 10 hours 16.9 g 0.33 11 hours 16.7 g 0.45 26.5 hours 17.0 g 0.60 (RV as used herein refers to reduced viscosity measured at 25"C on a solution of the polymer in dimethyl formamide containing 1 g of polymer in dimethyl formamide containing 1 g of polymer in 100 cm3 of solution).

The total weight of sample solution removed was thus 170.4 g.

The remainder of the reaction mixture was subjected to vacuum distillation to remove trifluoromethane sulphuric acid, the conditions being as follows: Time Pressure Head temp Pot temp Bath temp (min) (mum) (oc) (oc) (oc) start 5 54 62 78 5 4 58 67 96 15 5 60 72 96 20 5 61 72 96 25 6 61 75 96 35 5.5 65 78 96 45 3 65 82 104 55 7 64 85 104 65 10 69 91 110 75 5 70 92 110 95 7 80 95 120 The amount of distillate obtained was 199.7 g. This was redistilled at atmospheric pressure to yield 171 g of trifluoromethane sulphuric acid (b.p. 156-1 590C), the recovery from the available reaction mixture (after sampling) therefore being about 60%.

The residue from the vacuum distillation was substantially a solution of polymer in orthophosphoric acid (produced from the P205 and the water formed during the reaction). The solution was worked up as per the samples to yield 30.5 g of polymer having RV 0.36 and consisting predominantly of the repeat units having the formula set out above.

Claims

1. A process for the manufacture of an aromatic polysulphone or polyketone which comprises producing the aromatic polysulphone or polyketone as a solution or dispersion in trifluoromethane sulphonic acid using said sulphuric acid as a reaction solvent or dispersant and as a polymerisation catalyst, providing for phosphoric acid to be present in said solution or dispersion, removing trifluoromethane sulphuric acid by distillation from the solution or dispersion so as to leave a solution of the polymer in the phosphoric acid and recovering the distilled trifluoromethane sulphonic acid, and isolating the polymer from its solution in phosphoric acid.

2. A process according to claim 1 wherein the phosphoric acid provided is orthophosphoric acid (H3PO4).

3. A process according to either claim 1 or claim 2 wherein at least some of the phosphoric acid is provided by adding the acid directly to the solution or dispersion or by adding reactants to the solution or dispersion which form the acid.

4. A process according to any one of the preceding claims wherein at least some of the phosporic acid is provided as a result of being formed during the polymerisation reaction.

5. An aromatic polysulphone or polyketone when produced by a process according to any one of the preceding claims.