GB1559855A

GB1559855A - Manufacture of aromatic polymers

Info

Publication number: GB1559855A
Application number: GB2994976A
Authority: GB
Original assignee: Imperial Chemical Industries Ltd
Current assignee: Imperial Chemical Industries Ltd
Priority date: 1976-07-19
Filing date: 1976-07-19
Publication date: 1980-01-30
Also published as: JPS5312991A

Description

(54) MANUFACTURE OF AROMATIC POLYMERS (71) We, IMPERIAL CHEMICAL INDUSTRIES LIMITED, Imperial Chemical House, Millbank, London, SW1P 3JF, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to the manufacture of aromatic polymers and in particular to the manufacture of aromatic polyethersulphones and/or ketones.

In United Kingdom patent specification 1 417 664 it is disclosed that dialkali metal salts of bisphenols could be polymerised by heating with a substantially equimolar amount of certain aromatic dihalides in the absence of a diluent. It was also disclosed that the dialkali metal salts could be made by reaction of the bisphenol with a base, e.g. KOH, in a suitable solvent.

We have now found that a substantially equimolar mixture of a bisphenol and such a dihalide may be polymerised in the absence of a diluent by heating with an alkali metal carbonate.

Polymerisation of such bisphenol/dihalide mixtures by reaction with an alkali metal carbonate is disclosed in Canadian patent specification 847 963. It is suggested in the Canadian patent that the polymerisation proceeds via formation of the mono salt of the bisphenol and little bisphenate is produced.

In the process described in the Canadian patent a solvent such as sulpholane (tetramethylene sulphone) was employed. The use of such a solvent is undesirable on economic grounds (requiring expensive solvent recovery equipment) and also such solvents may give rise to coloured polymers.

Therefore according to the present invention we provide a process for the production of an aromatic polyethersulphone or ketone comprising heating to effect a polymerisation reaction a substantially equimolar mixture of a) at least one bisphenol of formula

in which Y is a direct link, oxygen, sulphur, --SO,,-, --COO-, or a divalent hydrocarbon radical and b) at least one aromatic dihalide of formula

in which X and X', which may be the same or different, are halogen atoms and are ortho or para to the groups Q and Q', Q and Q' which may be the same or different, are CO or -SO,-, Ar is a divalent aro- matic radical, and n is 0, 1, 2 or 3, with substantially 1 mole of an alkali metal carbonate per mole of bisphenol, or substantially 2 moles of an alkai metal bicarbonate per mole of bisphenol, said heating being carried out in the absence of a diluent for at least the initial part of the polymerisation reaction.

The halogen atoms X and X' are preferably chlorine, fluorine or bromine. Chlorine is preferred for cost reasons although the fluorides generally react faster. The halogen atoms are preferably para to the groups Q and Q'.

The aromatic radical Ar is preferably a divalent aromatic radical selected from phenylene, biphenylylene and terphenylylene.

Preferred dihalides have the formula

where m is 1, 2 or 3.

Examples of suitable dihalides include 4,4' - dichlorodiphenylsulphone 4,4' - difluorodiphenylsulphone 4,4' - dichlorobenzophenone bis - 4,4' - (4 - chlorophenylsulphonyl) biphenyl.

The process of the invention may employ only one aromatic dihalide so as to produce homopolymers. Mixtures of dihalides may also be employed so as to produce copolymers.

Examples of mixtures that may be employed include 4,4' - dichlorodiphenylsulphone with 4,4' - dichlorobenzophenone or bis - 4,4' - (4 chlorophenylsulphonyl)biphenyl.

Bisphenols that may be employed are those having the formula

where Y is as previously defined.

Preferred bisphenols include 4,4' - dihydroxybenzophenone 4,4' - dihydroxydiphenylsulphone 2,2,' - bis - (4 - hydroxyphenyl)propane 4,4' - dihydroxybiphenyl.

If desired some or all of the aromatically bound hydrogen atoms in the dihalide and/ or bisphenol may be substituted by inert groups such as alkyl or alkoxy (containing 1 to 4 carbon atoms).

Sodium and potassium carbonates and bi carbonates are the preferred alkali metal car carbonates although the sodium compounds give slower reactions, potassium carbonate is particularly preferred. The alkali metal carbonate is preferably anhydrous, if a hydrated carbonate is employed, the water should be removed, e.g. by heating under reduced pressure before high polymerisation temperatures are reached.

Where no diluent is employed throughout the polymerisation reaction the polymerisation temperature employed should be sufficiently high to keep the reaction mixture (including the polymer being formed) molten: thus as the reaction proceeds the temperature may need to be increased to keep the polymer formed molten. Generally when no diluent is employed polymerisation temperatures in excess of 250"C are required. The polymerisation temperature is preferably less than 400"C.

While it is preferable from economic and quality considerations to conduct the whole of the polymerisation reaction in the absence of a diluent, the reaction mixture in some cases becomes extremely viscous as poly merisation proceeds, for this reason the polymerisation reaction is initially carried out in such cases in theabsence of a diluent and then a suitable solvent is added during the course of the reaction. Preferred solvents are Nmethyl pyrrolidone, dimethyl sulphone and aromatic sulphones of the formula

where W is a direct link, an oxygen atom or two hydrogen atoms (one attached to each benzene ring) and Z and Z', which may be the same or different, are hydrogen atoms or phenyl groups.

The amount of alkali metal carbonate or bicarbonate employed should be substantially 1 mole per mole of bisphenol or 2 moles per mole of bisphenol respectively. A slight excess (e.g. up to 5 mol % excess-i.e. up to a total of 1.05 moles of carbonate per mole of bisphenol or a total of 2.1 moles of bicarbonate per mole of bisphenol) may be used. The use of larger amounts of alkali metal carbonate or bicarbonate is undesirable as it may cause cleavage of the polymer produced-thus giving rise to low molecular weight and/or branched products. The use of too little alkali metal carbonate or bicarbonate (less than 1 mole per mole of bisphenol or 2 moles per mole of bisphenol respectively) is undesirable as then only low molecular weight products may be obtained as a result of end stopping of the growing polymer chain by the effective excess of dihalide. The amount of alkali metal carbonate or bicarbonate should therefore preferably be between 1 and 1.05 moles of carbonate, or 2 and 2.1 moles of bicarbonate, per mole of bisphenoL The bisphenol and dihalide should be used in substantially equimolar amounts. An excess of one over the other leads to the production of low molecular weight products. However a slight excess, up to 5 mol Ós of dihalide may be employed if desired.

The polymerisation reaction when con ducted wholly in the melt in the absence of any diluent becomes very viscous as poly merisation proceeds, so that at least the latter part of the reaction is preferably carried out in an extruder.

The reaction may be terminated by mixing a suitable end stopping reagent, e.g. a mono or polyfunctional halide such as methyl chlor ide, t-butyl chloride or 4,4' - dichlorodiphenyl sulphone with the molten reaction mixture.

In the reaction, alkali metal halide is pro duced as a byproduct. This can be removed by comminuting the reaction product and leaching out the alkali metal halide with a suitable solvent, e.g. water.

Polymers prepared by the process of the present invention are particularly suitable for use in applications where the polymer is liable to be subject to high service temperatures.

Examples of such applications include electrical insulation, e.g. wire coatings, electrical connector mouldings, and cookware coatings.

The invention is illustrated by the following Example.

EXAMPLE 4,4' - dihydroxydiphenylsulphone (12.7 g, 0.05 moles), 4,4' - dichlorodiphenylsulphone (14.36 g, 0.05 moles) and anhydrous potassium carbonate (6.91 g, 0.05 moles) were charged to a 3-necked flask (capacity 100 cm3) fitted with a stirrer, air condenser and nitrogen inlet.

The mixture was heated on an oil bath to 200 C under a nitrogen stream without stir ring to effect melting. When the temperature reached 200"C the stirrer was started and the mixture stirred at 200"C for two hours.

The temperature was raised to 260"C when some frothing occurred and the mixture be came more viscous. After 3-1/2 hours at 260"C the temperature was increased to 280"C when more frothing occurred. After 1/2 hour at 280"C the temperature was raised to 296"C whereat the frothing gradually sub sided and the mixture became slowly more viscous. After a further 6 hours at 290"C the mixture was too viscous to stir and was left unstirred at 290"C for a further 3 hours.

Throughout the reaction the mixture remained a pale off-white colour. The mixture was then cooled and the polymer isolated by dissolution in dimethyl formamide and precipitation. The polymer was washed with water and dried to give a white powder of reduced viscosity 0.20 as measured at 25"C on a solution in dimethyl formamide, said solution containing 1 g of polymer per 100 cm3 of solution.

WHAT WE CLAIM IS:- 1. A process for the production of an aromatic polyethersulphone or ketone comprising heating to effect a polymerisation reaction a substantially equimolar mixture of a) at least one bisphenol of formula

in which Y is a direct link, oxygen, sulphur, 502-, O-, or a divalent hydrocarbon radical and b) at least one aromatic dihalide of formula

in which X and X', which may be the same or different, are halogen atoms and are ortho or para to the groups Q and Q', Q and Q' which may be the same or different, are CO or -SO,-, Ar is a divalent aro- matic radical, and n is 0, 1, 2 or 3, with substantially 1 mole of an alkali metal carbonate per mole of bisphenol, or with substantially 2 moles of an alkali metal bicarbonate per mole of bisphenol, said heating being carried out in the absence of a diluent for at least the initial part of the polymerisation reaction.

2. A process according to claim 1 wherein the halogen atoms X and X' in the aromatic dihalide are pare to the groups Q and Q'.

3. A process according to claim 1 or claim 2 wherein the halogen atoms X and X' in the aromatic dihalide are chlorine or fluorine.

4. A process according to any one of the preceding claims wherein the aromatic radical Ar in the aromatic dihalide is selected from phenylene, biphenylene and terphenylene.

5. A process according to any one of the preceding claims wherein the at least one aromatic dihalide has the formula

where m is 1, 2 or 3.

6. A process according to claim 5 wherein the at least one aromatic dihalide is selected from 4,4' - dichlorodiphenylsulphone, 4,4'difluorodiphenylsulphone, 4,4' - dichlorobenzophenone and bis - 4,4' - (4 - chlorophenylsulphonyl)biphenyl, and mixtures of 4,4' - dichlorodiphenylsulphone with 4,4' - dichlorobenzophenone or bis - 4,4' - (4 - chlorophenylsulphonyl)biphenyl.

7. A process according to any one of the preceding claims wherein the at least one bisphenol is selected from 4,4' - dihydroxybenzophenone, 4,4' - dihydroxydiphenylsulphone, 2,2' - bis - (4 - hydroxyphenyl)propane and 4,4' - dihydroxybiphenyl.

8. A process according to any one of the preceding claims wherein the alkali metal carbonate or bicarbonate is potassium carbonate.

9. A process according to any one of the preceding claims wherein the amount of alkali metal carbonate or bicarbonate is between 1 and 1.05 moles of carbonate, or 2 and 2.1 moles of bicarbonate, per mole of bisphenol.

10. A process according to any one of the preceding claims wherein said heating to effect the polymerisation reaction is carried out in the absence of a diluent for the whole of the polymerisation reaction.

11. A process according to claim 10 wherein the polymerisation temperature is increased as the reaction proceeds to keep the polymer formed molten.

12. A process according to either claim 10 or claim 11 wherein the polymerisation temperatures is in excess of 250"C and less than 400"C.

13. A process according to any one of claims 1 to 9 wherein the initial part of said heating to effect the polymerisation reaction is carried out in the absence of a diluent and then a solvent selected from N-methyl pyrrolidone, dimethyl sulphone, and aromatic suiphones of the formula

where W is a direct link, an oxygen atom or two hydrogen atoms (one attached to each benzene ring) and Z and Z', which may be the same or different are hydrogen atoms or phenyl groups, is added during the course of the reaction.

14. A process according to claim 1 substantially as hereinbefore described and with particular reference to the Example.

15. Polymers when prepared by a process according to any one of the preceding claims.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Throughout the reaction the mixture remained a pale off-white colour. The mixture was then cooled and the polymer isolated by dissolution in dimethyl formamide and precipitation. The polymer was washed with water and dried to give a white powder of reduced viscosity 0.20 as measured at 25"C on a solution in dimethyl formamide, said solution containing 1 g of polymer per 100 cm3 of solution. WHAT WE CLAIM IS:-

1. A process for the production of an aromatic polyethersulphone or ketone comprising heating to effect a polymerisation reaction a substantially equimolar mixture of a) at least one bisphenol of formula

where m is 1, 2 or 3.