IE910467A1 - Process for the preparation of polyphosphazenes by¹substitution of polydichlorophosphazene - Google Patents

Abstract

Process for the preparation of polyphosphazene by substitution of polydichlorophosphazene by means of a nucleophilic agent in hydrocarbon medium. According to this process the reaction is performed in the presence of a polyether. The process makes it possible to obtain a high degree of substitution.

Description

The invention relates to a process for the preparation of polyphosphazenes by substitution of poly5 dichlorophosphazene in a hydrocarbon medium.

Polyphosphazenes represent a family of polymers consisting of an inorganic phospho-nitrogen chain, the phosphorus atom carrying substituents of varied nature. These polymers may in particular comprise a plurality of units of formula: — R —I _ I R J (1) in which the symbols R, which may be identical or different within a single unit or from one unit to another, may represent radicals chosen from the group comprising alkyl, aryl, alkoxy, fluoroalkoxy, aryloxy, alkylsulphide or arylsulphide, alkylamino or arylamino radicals.

These polymers are obtained from the polydichlorophosphazene (II) by replacing the chlorine atoms by compounds having a nucleophilic character, in accor20 dance with the equation: r— Cl -1 I 1 r I — N = P — 1 — (II) + XR - 1 T» 1 = P — 1 1 *— Cl — L I R — + xci IE 91467 X denoting, in particular, a hydrogen atom or an alkali metal and R having the meaning given above.

Numerous nucleophilic compounds XR are described in the literature. The main compounds are the phenates and the alcoholates (more particularly the fluorinated alcoholates) combined with the sodium ion.

Two types of reaction medium are proposed in order to carry out the replacement: - Ethers (tetrahydrofuran, ethylene glycol ethers, 10 dioxane) which enable the reaction to be carried out in homogeneous phase (H.R. Allcock et al. Inorg. Chem. 5 (10), 1709, 15, (1966) Austin et al. Macromolecules 16. (5), 719-22 (1983)).

- Hydrocarbons in which the phenates and the 15 alcoholates are insoluble or partially soluble (Austin et al. Macromolecules 16 (5), 719-22 (1983), H.R. Penton US 4,514,550).

The replacement in a hydrocarbon medium (benzene, toluene, xylene, cyclohexane, etc. ...) has many ad20 vantages over an ether medium, amongst which the following may be mentioned: lower cost and frequently lower toxicity, ease of drying, less degradation of the polymer during the substitution, and ease of removal of the sodium chloride formed as by-product of the replacement, either by washing the reaction mixture with water or by simple filtration.

On the other hand, whatever the hydrocarbon, some nucleophilic agents are completely insoluble therein and because of this fact are incapable of reaching the IE 91467 chlorine atoms beyond a certain degree of conversion. The polyphosphazene retains a high proportion of residual chlorine and, during the extractions and washings, a partial degradation of the polymer results, which gives rise to a lower molecular mass. A relatively low replacement yield also results.

Moreover, the replacement of chlorine atoms in the polydichlorophosphazene by alcoholates presents particular problems. It is known that, simultaneously with the replacement, a competitive chain-breaking reaction takes place which tends to greatly reduce the average molecular mass and to produce a fraction of very low mass. Now, this competitive degradation reaction is much more pronounced with the alcoholates than with the phenates. The fluorinated alcoholates also present the problem of their degradation by attack on their fluorine atoms by their own alcoholate functional group. Thus, the yields indicated in the literature for replacement by fluorinated alcohols in an ethereal medium are very low (H.R. Allcock et al. Inorg. Chem. 5 (10), 1709, 15, (1966) or K.A. Reynard et al. US 3,896,058).

These problems which are particular to replacement by alcoholates may be minimised by carrying out the replacement in a hydrocarbon medium and at a temperature which is as low as possible, so as to reduce the nucleophilic character and thus the reactivity of the alcoholate anions. However, by carrying out the reaction under these conditions, it is not possible to achieve a complete replacement of the chlorine atoms because the jE 91467 insolubility of the alcoholates is more complete the lower the temperature at which the reaction is carried out.

In order to resolve these problems associated 5 with the lack of solubility both of some phenates and of alcoholates, P.E. Austin et al. Macromolecules 16 (5), 719-22 (1983) have proposed carrying out the replacement in the presence of quaternary ammonium salts.

In the case of phenates, this process does not 10 allow the reaction to be carried out exclusively in the presence of hydrocarbon as the solvent without the replacement stopping at an inadequate degree of conversion and thus without a high proportion of residual chlorine in the final polymer. The thermal stability of the quaternary ammonium salts is, in fact, too restricted to permit operation for prolonged periods at the high temperatures required for the substitution by phenates having a high steric hindrance. To be sure the use of quaternary ammonium salts enables the replacement by alcoholates to be carried out in a purely hydrocarbon medium, but the yields remain low (P.E. Austin et al. Macromolecules 16 (5), 719-22 (1983)).

The invention therefore proposes a process for the preparation of polyphosphazene by replacement of the chlorine atoms in polydichlorophosphazene.

It proposes in particular a process permitting a high degree of substitution by means of alkali metal phenates and alcoholates.

It proposes a process leading to a high yield of IE 91467 - 5 substituted polymer.

Further advantages of the process according to the invention will become apparent on reading the text which follows.

The process according to the invention consists in effecting the replacement of the chlorine atoms in a polydichlorophosphazene by means of nucleophilic agents, carrying out the reaction in a hydrocarbon medium, and is characterised in that the substitution reaction is carried out entirely or partially in the presence of a polyether.

In general, the polyether may be used in a proportion of at least 0.1% by weight relative to the nucleophilic reagent. Preferably, this proportion does not exceed 10%.

In order to have an adequate efficacy, the polyethers must consist of a chain comprising a number of ether groups which is at least equal to 4. This chain may be terminated at each end by a hydroxyl group or by an ether group or may be terminated by a hydroxyl group at one end and an ether group at the other end.

This chain may, in particular, consist of linked ethylene oxide or propylene oxide or a combination of the two.

These polyethers, which will be termed catalyst below, may be represented by the following formula: *1 - 0-p ^χΗ2χ - 0 4- R2 (III) — n IE 91467 _ , _ 6 in which n represents a number at least equal to 4, x represents 2 or 3 and the symbols Rx and R2, which may be identical or different, may represent a hydrogen atom, an alkyl radical containing from 1 to 24 carbon atoms, a monocyclic or polycyclic aryl radical containing up to 18 carbon atoms or an alkylaryl or aralkyl radical in which the alkyl and aryl parts are as defined above.

In this formula III, n is generally greater than 20 and preferably between 50 and 200.

Amongst these polyethers, the following will be mentioned very particularly: polyethers of formula III in which one of the symbols Rx or R2 represents a hydrogen atom and the other represents an alkylaryl radical and in particular an alkylaryl radical containing from 8 to 20 carbon atoms.

According to the invention, the introduction of the catalyst may be carried out at any time during the substitution. It may be carried out from the start, at the same time as the introduction of the other reagents.

It may also be carried out after a time sufficient to allow a conversion which is as complete as possible in the absence of this catalyst.

As has been specified, the substitution reaction is carried out in a hydrocarbon medium and the latter may consist of an aromatic, cycloaliphatic or aliphatic hydrocarbon, such as one of the hydrocarbons mentioned above, or a mixture of hydrocarbons.

It would not go beyond the scope of the invention to use, as solvent for the substitution mixture, a Ί IE 91467 mixture of hydrocarbons and ethers, it being possible for the latter to be chosen, for example, from the products mentioned above. The introduction of ethereal solvents may be carried out initially as a mixture with the hydrocarbon or in the mixture during the substitution reaction.

The substitution reaction is generally carried out at a temperature of between about 0°C and 220°C, depending, in particular, on the nucleophilic agent used, at a pressure fixed by the vapour pressure of the solvent.

The implementation of the process according to the invention enables polyphosphazenes to be obtained with a high polymer yield and a substitution yield of close to 100% and in all cases higher than 95%, the said polymer, which is another subject of the invention, possessing a high molecular mass.

EXAMPLE 1 (comparative) la/ 18.13 g (0.193 mol) of phenol and 225 g of xylene are introduced into a reactor pressurised under nitrogen; 50 g of xylene are distilled so as to ensure dehydration of the mixture. The moisture content is thus reduced to less than 10 ppm. 5.15 g (0.172 mol) of sodium hydride are added to this solution. The reaction for formation of sodium phenate is carried out in 2 hours at 140°C, with stirring. lb/ The suspension of sodium phenate in xylene is cooled to 120°C. 9.06 g (0.156 chlorine equivalent) of polydichlorophosphazene in solution in 18 g of IE 91467 trichlorodiphenyl are introduced at this temperature. The mixture is allowed to react for 24 hours at 140°C.

The reaction mixture is then neutralised with concentrated HCI and filtered on a layer of infusorial earth. The xylene is evaporated until a syrup is obtained and the remainder is poured into 500 ml of methanol. After draining, the polymer is redissolved in the minimum amount of tetrahydrofuran (THF) and reprecipitated from 500 ml of methanol. The latter operation is repeated once more. The final polymer is finally dried at 80°C under vacuum (absolute pressure brought back to 133.32 Pa). 12.86 g of polydiphenoxyphosphazene are obtained, which is a yield of 71.3%. This polymer has the following characteristics: residual chlorine content : 0.64% by weight intrinsic viscosity : 64.3 ml/g Mw (by light scattering) : 530,000 EXAMPLE 2 The preparation of sodium phenate is carried out by method la, using 18.24 g (0.194 mol) of phenol, 225 g of xylene and 5.16 g (0.172 mol) of sodium hydride as the starting material.

The substitution reaction is carried out in accordance with lb, using 8.88 g (0.153 chlorine equivalent) of the same polydichlorophosphazene. The reaction mixture is then kept at 140°C for 20 h. 0.44 g of nonylphenol ethoxylated with 100 molecules of ethylene oxide per one mole of nonylphenol (2.2% relative to the weight of sodium phenate) is then IE 91467 , - 9 added. The reaction mixture is kept at 120°C for 20 hours.

The polydichlorophosphazene is isolated and purified by the process described in lb. 14.78 g (yield: 83.6%) of a polymer are obtained, the analytical characteristics of which are as follows: residual chlorine content : 0.062% by weight intrinsic viscosity : 83.6 ml/g Mw (by light scattering) : 809,000 EXAMPLE 3 4,445 g of toluene, 14,504 g of xylene and a mixture of phenols comprising 49.94 g of eugenol (0.304 mol), 496 g of phenol (5.271 mol) and 815 g of p-ethylphenol (6.671 mol) are introduced into a 30-1 reactor fitted with a turbine stirrer and pressurised under nitrogen. This solution is dried by distilling off 5,266 g of solvent (moisture content brought back to less than 10 ppm). 253 g of sodium (11 mols) are then introduced. The mixture is brought to reflux and the stirring speed is increased progressively up to 3,000 rev/min. The evolution of hydrogen ceases completely at the end of 40 min and all of the operating conditions are maintained for a further 2 hours.

The reaction mixture is cooled to 110°C and 571.83 g of polydichlorophosphazene (9.86 Cl equivalents) in solution in 1,235 g of trichlorobenzene are introduced into the mixture. The whole is kept at 120°C for 20 hours, at the end of which 32 g of nonylphenol ethoxylated with 100 molecules of ethylene oxide are IE 91467 __,__s :· - 10 added. The reaction mixture is kept at 120 °C for a further 20 hours.

After cooling, the mixture is slightly acidified by adding concentrated HCl and filtered on a filter covered with a layer of infusorial earth. It is then concentrated to about one third of its volume and precipitated from 60 1 of methanol. The resin collected by precipitation is then washed in a blender with twice 7 1 of isopropanol, 1.5 1 and then 3 times 7 1 of ethylene glycol, 1.5 1 of isopropanol and finally 7 1 of isopropanol. The washed resin is brought to dryness in an oven at 80°C under vacuum (absolute pressure of 66.6 Pa). 1,019 g of polymer are obtained (which is a yield of 77.4%), the characteristics of which are as follows: residual chlorine content : 99 ppm intrinsic viscosity : 77 ml/g Mw (by light scattering) : 880,000 EXAMPLE 4 A suspension containing 16.10 g of a 58.5% dispersion of NaH in oil (which is 9.42 g or 0.392 mol of pure NaH) and 201.30 g of benzene is produced in a reactor pressurised under nitrogen. While keeping the temperature of the reactor at 4°C, a solution containing 29.40 g (0.294 mol) of trifluoroethanol, 30.53 g (0.151 mol) of an alcohol of formula H(CF2)34CH2OH and 106.54 g of benzene is then introduced. This addition is effected in the course of 2 hours. The reaction mixture is kept at a temperature of 4°C for a further 4 hours, with stirring.

IE 91467 19.72 g of polydichlorophosphazene (which is 0.340 chlorine equivalent) in solution in 75.98 g of benzene are then added. This addition is effected in the course of 10 min while keeping the temperature of the 5 reactor at between 6 and 7°C. At the end of 30 min, the reaction mixture is allowed to return to ambient temperature and a solution containing 1.4 g of nonylphenol ethoxylated with 100 molecules of ethylene oxide and 360 g of THF is added. The reaction mixture is kept at 10 30°C for 1.5 hours. The temperature is raised progressively in the course of 2 hours up to 47°C. The reaction mixture is finally left to stand for 18 hours at ambient temperature.

The whole is then neutralised by the addition of 15 N HCI and evaporated to dryness, the residue is dissolved in acetone and the solution is filtered to remove NaCl. The filtrate is concentrated to about 70 ml and precipitated from 500 ml of hexane. The precipitate is twice redissolved in acetone, the solution is concentrated and precipitated from hexane and the precipitate is then dried at 80eC under vacuum (absolute pressure of 133.32 Pa). 47.45 g (yield 90.7%) of a polymer are thus obtained, the characteristics of which are as follows: IE 91467 - 12 residual chlorine content intrinsic viscosity Mw (by light scattering) : 222 ppm : 65.6 ml/g : 1,000,000 IE 91467 CLAIMS

Claims (13)

1. Process for the preparation of polyphosphazene by replacement of the chlorine atoms in polydichlorophosphazene by means of nucleophilic agents, carrying out the 5 reaction in a hydrocarbon medium, characterised in that the substitution reaction is carried out entirely or partially in the presence of a polyether.

2. Process according to Claim 1, characterised in that the polyphosphazene comprises a plurality of units 10 of formula R I p I R (I) in which the symbols R, which may be identical or different, within a single unit or from one unit to another, may represent alkyl, aryl, alkoxy, fluoroalkoxy, aryloxy, 15 alkylsulphide or arylsulphide, alkylamino or arylamino radicals.

3. Process according to either of Claims 1 and 2, characterised in that the nucleophilic agent is chosen from the compounds of formula XR, in which the symbol R 20 represents a hydrogen atom or an alkali metal.

4. Process according to any one of Claims 1 to 3, characterised in that the polyether has the formula: C X H 2X in which n represents a number at least equal to 4, x represents 2 or 3 and the symbols Ri and R 2 , which may be identical or different, may represent a hydrogen atom, an alkyl radical containing from 1 to 24 carbon atoms, a 5. Monocyclic or polycyclic aryl radical containing up to 18 carbon atoms or an alkylaryl or aralkyl radical in which the alkyl and aryl parts have the meaning given above.

5. Process according to Claim 4, characterised in that n is greater than 20 and preferably between 50 and 10 200.

6. Process according to either of Claims 4 and 5, characterised in that one of the symbols R x and R 2 represents a hydrogen atom and the other represents an alkylaryl radical containing 8 to 20 carbon atoms. 15

7. Process according to any one of Claims 1 and 6, characterised in that the polyether is present in the reaction mixture from the start of the substitution reaction.

8. Process according to any one of Claims 1 to 6, 20 characterised in that the polyether is introduced into the reaction mixture during the substitution reaction.

9. Process according to any one of Claims 1 to 8, characterised in that the substitution mixture comprises an aromatic, cycloaliphatic or aliphatic hydrocarbon or 25 a mixture comprising several hydrocarbons.

10. Process according to Claim 9, characterised in that the substitution mixture comprises a mixture of hydrocarbon and ether. IE 91467

11. The polyphosphazenes as obtained by application of the process according to any one of Claims 1 to 10.

12. A process according to Claim 1 for the preparation of polyphosphazene, substantially as hereinbefore described and exemplified.

13. Polyphosphazene whenever obtained by a process claimed in Claim 12.