METHOD FOR MANUFACTURING

1 ,4-BIS (4-PHENOXYBENZOYUBENZENE USING SUBSTANTIALLY NON-HYDROLYZED TEREPHTHALOYL CHLORIDE

TECHNICAL FIELD

The present application relates to a method for manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene, as well as a method for manufacturing polyaryl etherketone polymers, in particular polyether ketone ketone polymers, starting from said 1 ,4-bis(4-phenoxybenzoyl)benzene.

TECHNICAL BACKGROUND

Polyether ketone ketone (abbreviated name: PEKK) polymers have a number of properties which make them useful for applications involving exposure to high temperature or to high mechanical or chemical stress. They are for instance useful in the aerospace industry, in off-shore drilling and in medical devices.

One known route for manufacturing polyether ketone ketone polymers relies on the use of 1 ,4-bis(4-phenoxybenzoyl)benzene as a starting material.

1 ,4-bis(4-phenoxybenzoyl)benzene can be prepared by reacting terephthaloyl chloride and diphenyl ether in the presence of a Lewis acid such as aluminum trichloride.

In document US 4,816,556 (example 2), 1 ,4-bis(4-phenoxybenzoyl)benzene is prepared by dissolving terephthaloyl chloride and diphenyl ether in ortho-dichlorobenzene and adding aluminum chloride. Thereafter, cold methanol is added so as to produce a slurry which is filtered, reslurried in methanol and filtered again.

In document US 4,826,947 (example 2), 1 ,4-bis(4-phenoxybenzoyl)benzene is prepared by providing a mixture of methylene chloride, methylsulfone and aluminum trichloride, adding diphenyl ether and thereafter terephthaloyl chloride. The reaction mixture is then poured into cold methanol so as to make a slurry which is then filtered.

Document WO 95/23821 (example 1 1 ) discloses providing aluminum chloride in ortho-dichlorobenzene and then adding terephthaloyl chloride and diphenyl ether. Thereafter, the reaction mixture is allowed to warm up to room temperature, stirred, and poured into a methanol concentrated HCI solution. A precipitate is formed which is subsequently filtered off.

There is still a need for new methods for manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene with a high purity and a high yield, which can be implemented at the industrial scale in an economically realistic manner.

SUMMARY

It is a first object of the invention to provide a method for manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene, comprising:

- providing a solvent, a Lewis acid, a first reactant and a second reactant,

wherein the first reactant and the second reactant are respectively terephthaloyl chloride and diphenyl ether, or reversely;

wherein the terephthaloyl chloride is of a purity grade such that, 10 minutes after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 100 NTU;

- mixing the first reactant in the solvent to make a starting mixture; and,

- adding the second reactant to the starting mixture;

wherein the Lewis acid is mixed, at least partly, to the starting mixture before adding the second reactant to the starting mixture, and/or

wherein the Lewis acid is mixed, at least partly, with the second reactant and added together to the starting mixture; so as to obtain a product mixture comprising a 1 ,4-bis(4- phenoxybenzoyl)benzene-Lewis acid complex.

In some embodiments, the terephthaloyl chloride is of a purity grade such that:

- 10 minutes after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 50 NTU, and preferably of less than 10 NTU;

- preferably, 10 hours after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 100 NTU, more preferably of less than 50 NTU and even more preferably of less than 10 NTU; and

- more preferably, 24 hours after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 100 NTU, more preferably of less than 50 NTU and even more preferably of less than 10 NTU.

In some embodiments, the terephthaloyl chloride is kept in a sealed container without contact with ambient air before use.

In some embodiments, the diphenyl ether and solvent, in combination, contain less than 500 ppm by weight of water, advantageously less than 250 ppm by weight of water, preferably less than 150 ppm by weight of water, more preferably less than 100 ppm by weight of water, and most preferably less than 50 ppm by weight of water.

In some embodiments, the diphenyl ether and solvent, in combination, contain from 1 to 250 ppm by weight of water, preferably from 2 to 200 ppm by weight of water, more preferably from 3 to 150 ppm by weight of water, even more preferably from 4 to 100 ppm by weight of water and most preferably from 5 to 50 ppm by weight of water.

In some embodiments, the method comprises a step of drying the solvent and/or the diphenyl ether before use, preferably by distillation or by contacting with a molecular sieve or with a dehydrating agent.

In some embodiments, the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration in the solvent which is higher than the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex during at least part of the reaction of the terephthaloyl chloride with the diphenyl ether.

In some embodiments, the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration which is higher by at least 5 %, preferably by at least 10 %, more preferably by at least 20 %, than the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex, during part of the reaction of the terephthaloyl chloride with the diphenyl ether.

In some embodiments, the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration of more than 5 wt.%, preferably more than 10 wt.%, more preferably more than 15 wt.%, and most preferably more than 30 wt.%, during part of the reaction of the terephthaloyl chloride with the diphenyl ether.

In some embodiments, the Lewis acid is aluminum trichloride.

In some embodiments, the solvent is different from diphenyl ether, terephthaloyl chloride or the Lewis acid. The solvent may advantageously be ortho-dichlorobenzene.

On the contrary, in some other embodiments, the solvent is either diphenyl ether, terephthaloyl chloride or the Lewis acid. The solvent may advantageously be diphenyl ether.

In some embodiments, the second reactant is terephthaloyl chloride. The Lewis acid is mixed with terephthaloyl chloride and added together to the starting mixture.

In some embodiments, the first reactant is terephthaloyl chloride. The Lewis acid is mixed with the starting mixture before adding the diphenyl ether to the starting mixture.

In some embodiments, the method of the invention comprises one or more steps for purifying 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex from the product mixture.

The invention also relates to a method of making a polyether ketone ketone polymer, comprising:

- manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene according to the method of anyone of the disclosed embodiments;

- reacting said 1 ,4-bis(4-phenoxybenzoyl)benzene with at least one difunctional aromatic acyl chloride.

Independently from the above, the invention additionally provides the following items:

Item 1. A method for manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene, comprising:

- providing a solvent, a Lewis acid, a first reactant and a second reactant,

wherein the first reactant and the second reactant are respectively terephthaloyl chloride and diphenyl ether, or reversely, and

wherein the diphenyl ether and solvent, in combination, contain less than 500 ppm by weight of water;

- mixing the first reactant in the solvent to make a starting mixture; and,

- adding the second reactant to the starting mixture;

wherein the Lewis acid is mixed, at least partly, to the starting mixture before adding the second reactant to the starting mixture, and/or

wherein the Lewis acid is mixed, at least partly, with the second reactant and added together to the starting mixture; so as to obtain a product mixture comprising a 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex.

Item 2. The method of item 1 , wherein the diphenyl ether and solvent, in combination, contain less than 250 ppm by weight of water, preferably less than 150 ppm by weight of water, more preferably less than 100 ppm by weight of water, and most preferably less than 50 ppm by weight of water.

Item 3. The method of item 1 or item 2, wherein the terephthaloyl chloride is of a purity grade such that, 10 minutes after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 500 NTU.

Item 4. The method of any of items 1 to 3, wherein the terephthaloyl chloride is of a purity grade such that:

- 10 minutes after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 200 NTU, preferably of less than 100 NTU, more preferably of less than 50 NTU, and most preferably of less than 10 NTU;

- preferably, 10 hours after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 500 NTU, preferably of less than 200 NTU, more preferably of less than 100 NTU, even more preferably of less than 50 NTU and most preferably of less than 10 NTU; and

- more preferably, 24 hours after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 500 NTU, preferably of less than 200 NTU, more preferably of less than 100 NTU, even more preferably of less than 50 NTU and most preferably of less than 10 NTU.

Item 5. The method of any of items 1 to 4, wherein the diphenyl ether and solvent, in combination, contain from 1 to 250 ppm of water, preferably from 2 to 200 ppm by weight of water, more preferably from 3 to 150 ppm by weight of water, even more preferably from 4 to 100 ppm by weight of water and most preferably from 5 to 50 ppm by weight of water.

Item 6. The method of any of items 1 to 5, comprising a step of drying the solvent and/or a step of drying the diphenyl ether before use, preferably by distillation or by contacting with a molecular sieve or with a dehydrating agent.

Item 7. The method of any of items 1 to 6, wherein the terephthaloyl chloride is kept in a sealed container without contact with ambient before use.

Item 8. The method of any of items 1 to 7, wherein the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration in the solvent which is

higher than the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex during at least part of the reaction of the terephthaloyl chloride with the diphenyl ether.

Item 9. The method of any of items 1 to 8, wherein the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration which is higher by at least 5 %, preferably by at least 10 %, more preferably by at least 20 %, than the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex, during part of the reaction of the terephthaloyl chloride with the diphenyl ether.

Item 10. The method of any of items 1 to 9, wherein the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration of more than 5 wt.%, preferably more than 10 wt.%, more preferably more than 15 wt.%, and most preferably more than 30 wt.%, during part of the reaction of the terephthaloyl chloride with the diphenyl ether.

Item 1 1. The method of any one of any of items 1 to 10, wherein the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent during at least 75 %, preferably at least 90 %, more preferably at least 95 % of the duration of the reaction of the terephthaloyl chloride with the diphenyl ether, and most preferably during the totality of the reaction of the terephthaloyl chloride with the diphenyl ether.

Item 12. The method of any one of any of items 1 to 1 1 , wherein the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent when an amount of 1 ,4-bis(4-phenoxybenzoyl)benzene of 75 mol.%, relative to the initial amount of terephthaloyl chloride, is present in the starting mixture; preferably the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent when an amount of 1 ,4-bis(4-phenoxybenzoyl)benzene of 80 mol.%, relative to the initial amount of terephthaloyl chloride, is present in the starting mixture; more preferably the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent when an amount of 1 ,4-bis(4-phenoxybenzoyl)benzene of 85 mol.%, relative to the initial amount of terephthaloyl chloride, is present in the starting mixture; and most preferably, the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the

solvent when an amount of 1 ,4-bis(4-phenoxybenzoyl)benzene of 90 mol.%, relative to the initial amount of terephthaloyl chloride, is present in the starting mixture.

Item 13. The method of any of items 1 to 12, wherein the Lewis acid is aluminum trichloride.

Item 14. The method of any one of items 1 to 13, wherein the Lewis acid, the first reactant or the second reactant plays the role of the solvent.

Item 15. The method of any of items 1 to 13, wherein the solvent is ortho dichlorobenzene.

Item 1 6. The method of any one of claims 1 to 15, wherein the second reactant is terephthaloyl chloride and,

wherein the Lewis acid is mixed with terephthaloyl chloride and added together to the starting mixture.

Item 17. The method of any one of items 1 to 15, wherein the first reactant is terephthaloyl chloride and,

wherein the Lewis acid is mixed with the starting mixture before adding the diphenyl ether to the starting mixture.

Item 18. The method of any of items 1 to 17, comprising the additional steps of:

- mixing the product mixture with a protic solvent so as to provide a product slurry;

- separating 1 ,4-bis(4-phenoxybenzoyl)benzene from the product slurry, preferably by filtration and optionally washing.

Item 19. A method of making a polyether ketone ketone polymer, comprising:

- manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene according to the method of any of items 1 to 18;

- reacting said 1 ,4-bis(4-phenoxybenzoyl)benzene with at least one difunctional aromatic acyl chloride.

The present disclosure provides a method for manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene with a high purity and a high yield. This method can be implemented at the industrial scale.

In a first aspect, it has been found that the quality of the terephthaloyl chloride used as a starting material is critical for achieving high purity and high yield in the manufacture of 1 ,4-bis(4-phenoxybenzoyl)benzene. In particular, one acyl chloride group or both acyl chloride groups in terephthaloyl chloride may react with water potentially present in the material’s environment. The presence of hydrolyzed forms of terephthaloyl chloride is undesirable for two reasons: first, the hydrolyzed portion of terephthaloyl chloride will not lead to the production of 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex; second, the hydrolyzed portion of terephthaloyl chloride tends to be insoluble in the solvent used for the reaction.

It is desirable to maintain the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex which is produced during the reaction as a supersaturated solution during at least part of the reaction, in order to achieve a high yield of 1 ,4-bis(4-phenoxybenzoyl)benzene and a low level of by-product impurities such as 4-(4-phenoxybenzoyl)benzoyl chloride and its corresponding carboxylic acid and ester forms. In this context, and without wishing to be bound by any theory, it is believed that the hydrolyzed portion of terephthaloyl chloride in the starting material may act as a nucleating agent for the precipitation of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex and thus prevent said complex from being maintained as a supersaturated solution during the reaction.

In a second aspect, it has been found that the presence of even relatively low amounts of water during the reaction of terephthaloyl chloride and diphenyl ether may lead to a relatively large decrease in reaction yield and / or in the purity of final product. The presence of water may indeed lead to the hydrolysis of the terephthaloyl chloride, which is undesirable for the reasons already set forth above. In addition, water droplets may also act as a nucleating agent of their own.

By maintaining the amount of water in the solvent and diphenyl ether below a desired threshold, the yield of 1 ,4-bis(4-phenoxybenzoyl)benzene may be increased, and the level of by-product impurities such as 4-(4-phenoxybenzoyl)benzoyl chloride and its corresponding carboxylic acid and ester forms may remain low.

In a third aspect, the two-step addition of the two reactants, namely terephthaloyl chloride and diphenyl ether, enable to obtain 1 ,4-bis(4-

phenoxybenzoyl)benzene-Lewis acid complex, and therefore 1 ,4-bis(4-phenoxybenzoyl)benzene, with a high purity and a high yield, in an efficient way. In particular, it enables to avoid any prior contacting time between the two reactants as in the methods of the prior art, in which the two reactants have to be first mixed together for several hours and heated before adding the second reactant. It also enables to reduce the production of unwanted by-products such as 4-(4-phenoxybenzoyl)benzoic acid or 4-(4-phenoxybenzoyl)benzoic acid ester.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig-1 shows the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex in ortho-dichlorobenzene, as a function of temperature. Temperature in °C is provided on the X axis. The weight concentration of 1 ,4-bis(4-phenoxybenzoyl)benzene at saturation is provided in the Y axis. The Lewis acid-to-1 ,4-bis(4-phenoxybenzoyl)benzene molar ratio is 4.05. The Lewis acid is aluminum trichloride.

Fig.2 schematically shows the evolution of the concentration of 4-(4-phenoxybenzoyl)benzoyl chloride (as defined below) (A), 1 ,4-bis(4-phenoxybenzoyl)benzene (B) and xanthydrol moiety-containing molecules (C), as a function of the progression of the reaction. The concentrations are provided in mol.% relative to the initial total amount of terephthaloyl chloride. The progression of the reaction is indicated in arbitrary units on the X-axis.

DESCRIPTION OF EMBODIMENTS

The embodiments of the invention will now be described in more detail without limitation in the following description.

1 ,4-bis(4-phenoxybenzoyl)benzene (abbreviated name: EKKE) is the compound of formula I :

It may be made by reacting together terephthaloyl chloride and diphenyl ether, hereafter called“first reactant” and“second reactant”. In some embodiment the first reactant is terephthaloyl chloride and the second reactant is diphenyl ether. On the contrary, in other embodiments, the first reactant is diphenyl ether and the second reactant is terephthaloyl chloride.

Terephthaloyl chloride is of formula II :

Diphenyl ether of formula III :

The reaction is carried out in a solvent, and in the presence of a Lewis acid, acting as a Friedel-Crafts catalyst. This is hereafter called“the reaction step”.

The reaction results in the production of the compound of formula I which is predominantly in the form of a complex with the Lewis acid.

It is believed that the reaction comprises two stages. In the first stage, one molecule of formula II reacts with one molecule of formula III to form the following intermediate of formula IV (4-(4-phenoxybenzoyl)benzoyl chloride) which is called an“active intermediate”:

(IV)

Then one molecule of the active intermediate of formula IV reacts with another molecule of formula III to form the desired product of formula I.

During the reaction, the following 4-(4-phenoxybenzoyl)benzoic acid of formula IVa can also be produced to some extent (notably from the active intermediate of formula IV):

(IVa)

The corresponding 4-(4-phenoxybenzoyl)benzoic acid ester can be formed either directly from the acyl chloride of formula IV or from the carboxylic acid of formula IVa. The acid form and/or the ester form of the intermediate can be formed during the reaction but they can also primarily be formed from the remaining active intermediate during subsequent workup (such as when the product mixture is mixed with a protic solvent, as described below).

The 4-(4-phenoxybenzoyl)benzoic acid and 4-(4-phenoxybenzoyl)benzoic acid ester are inactive and therefore remain as impurities in the product mixture.

The other main impurities produced by the reaction are xanthydrol moiety-containing molecules of formula (V):

(V)

In some embodiments, one of the two reactants or the Lewis acid can play the role of the solvent.

On the opposite, in other embodiments, the solvent can be a separate solvent than the diphenyl ether, the terephthaloyl chloride, or the Lewis acid. In these embodiments, the solvent is preferably a non-protic solvent, which can in particular be selected from methylene chloride, carbon disulfide, ortho-dichlorobenzene, meta-dichlorobenzene, para-dichlorobenzene, 1 ,2,4-trichlorobenzene, 1 ,2,3-trichlorobenzene, ortho-difluorobenzene, 1 ,2-dichloroethane, 1 ,1 -dichloroethane, 1 ,1 ,2,2-tetrachloroethane, tetrachloroethylene, dichloromethane, nitrobenzene and mixtures thereof.

Ortho-dichlorobenzene is a preferred solvent.

According to one aspect of the invention, the compound of formula II used as a starting material is provided with a high purity grade. Hydrolyzed forms of the compound of formula II are difficult to analyze and quantify in the starting material. It has been found that one practical method to ensure that the compound of formula II has the requisite purity is to dissolve it in a solvent, and to analyze its turbidity. It has been found that a high turbidity value in this test (which is indicative of a significant amount of insoluble contaminants within the starting material) results in a poor yield and a high amount of undesirable by-products in the manufacture of the compound of formula I.

Accordingly, the compound of formula II is preferably of a purity grade such that, 10 minutes after introducing it at a reference concentration of 6.5 wt.% in the solvent, at a temperature of 20°C, a solution is obtained having a turbidity of less than 500 NTU. Turbidity values are provided relative to a sample of solvent without compound of formula II.

In some embodiments, the solvent used in the turbidity test can be the same solvent as the reaction solvent. On the contrary, in other embodiments, the solvent used in the turbidity test can be a different solvent than the reaction solvent.

Preferably, the turbidity is less than 200 NTU, more preferably less than 100 NTU, even more preferably less than 50 NTU and most preferably less than 10 NTU.

A more stringent test consists in waiting for 10 hours, or even for 24 hours, between the introduction of the compound of formula II into the solvent and the turbidity measurement. Preferably, turbidity values of less than 500 NTU, preferably less than 200 NTU, more preferably less than 100 NTU, even more preferably less than 50 NTU and most preferably less than 10 NTU are obtained in this more stringent test.

In some variations, a second turbidity value may be obtained with a sample of solvent of so-called anhydrous grade; which is stored on a molecular sieve. Preferably, the anhydrous grade of solvent is characterized by a water weight content of less than 50 ppm, preferably of less than 30 ppm. In embodiments, the second, anhydrous turbidity value may be less than 500 NTU, preferably less than 200 NTU, more preferably less than 100 NTU, even more preferably less than 50 NTU and most preferably less than 10 NTU.

In other variations, the turbidity values indicated herein are obtained using a sample of the batch of solvent which is used for the reaction itself. This is particularly advantageous for the turbidity measurements conducted 10 hours or 24 hours after the introduction of the compound into the solvent, since the measurement is then representative of the actual quality of the compound in the reaction conditions, depending also on the quality of the solvent.

In a particular embodiment, the solvent used for the turbidity test is ortho dichlorobenzene containing less than 100 ppm by weight of water. The turbidity may be assessed by introducing 1580 mg of terephthaloyl chloride into 22.6 g of ortho-dichlorobenzene containing less than 100 ppm by weight of water in a 50 ml_ flask, and by agitating the mixture with a magnetic stirrer, under nitrogen atmosphere. After 10 minutes, the turbidity of the mixture may be measured on a 20 ml_ sample with a Hach Lange Turbidimeter, using the same solvent as a blank sample.

The ortho-dichlorobenzene used for the turbidity test can have a content by weight of water of from 50 to 75 ppm; or from 75 to 100 ppm. The ortho dichlorobenzene used for the turbidity test can also have a content by weight of water less than 50ppm, in particular from 1 to 5 ppm; or from 5 to 10 ppm; or from 10 to 20 ppm; or from 20 to 30 ppm; or from 30 to 40 ppm; or from 40 to 50 ppm.

A number of steps can be taken in order to ensure that the compound of formula II is of a satisfactory purity grade. In particular, the compound should substantially not be in contact with water at any time before the reaction. It can thus be advantageous to keep this material in a sealed container without contact with ambient air. Keeping the material in a nitrogen atmosphere may in particular be useful.

As a sealed container, use may in particular be made of a container having walls and a lid having a moisture vapor transmission rate of not more than 0.1 g/m2.24h at a relative humidity of 90% and a temperature of 37.8°C.

The container walls may be for instance made of polyethylene, such as high-density polyethylene.

The container walls may preferably have a thickness of at least 0.5 mm, more preferably at least 1 mm.

According to another aspect of the invention, the solvent and the compound of formula III used for the reaction have a low water content.

Accordingly, the solvent used for the reaction preferably contains less than 500 ppm by weight of water, advantageously less than 250 ppm by weight of water, preferably less than 150 ppm by weight of water, more preferably less than 100 ppm by weight of water, and most preferably less than 50 ppm by weight of water. In preferred variations, the above weight ranges also apply in a similar manner to the compound of formula III and the solvent in combination.

Possible weight ranges of water content in the solvent used for the reaction are: from 1 to 5 ppm ; or from 5 to 10 ppm ; or from 10 to 20 ppm ; or from 20 to 30 ppm; or from 30 to 40 ppm; or from 40 to 50 ppm; or from 50 to 75 ppm; or from 75 to 100 ppm ; or from 100 to 150 ppm ; or from 150 to 200 ppm ; or from 200 to 250 ppm; or from 250 to 300 ppm; or from 300 to 350 ppm; or from 350 to 400

ppm; or from 400 to 500 ppm. Ranges of from 1 to 250 ppm, or from 2 to 200 ppm, or from 3 to 150 ppm, or from 4 to 100 ppm, or from 5 to 50 ppm are particularly preferred. In preferred variations, the above weight ranges also apply in a similar manner to the compound of formula III and the solvent in combination.

A number of steps can be taken in order to ensure that the compound of formula III and/or the solvent do not contain an excessive amount of water. In particular, it is desirable to keep these materials in sealed containers without contact with ambient air. Keeping the materials in a dry nitrogen atmosphere may in particular be useful.

In some variations, the method of embodiments of the invention comprises a preliminary step of drying, i.e., reducing the water content, of the solvent and/or the compound of formula III, before use. This step may be performed, e.g., by distillation or by contacting with a molecular sieve or with a dehydrating agent.

By way of example, the weight proportion of water in the solvent, or in the solvent combined with the compound of formula III, may be reduced owing to the drying step from an initial value of 50 to 300 ppm to a final value of less than 100 ppm, preferably less than 50 ppm, more preferably less than 30 ppm.

The Lewis acid used in the method of embodiments of the invention is preferably of a purity grade such that it comprises less than 0.1 wt.% insoluble matter, and more preferably less than 0.05 wt.% insoluble matter, as measured by gravimetry, when introduced into the solvent at a concentration of 5 wt.% and substantially dissolved under agitation.

The reaction between the compounds of formulas II and III to make the compound of formula I may be performed in a reactor. The reactor can be for instance a glass reactor, a glass-lined reactor or a stainless-steel reactor.

Preferably, the reaction may be performed under a substantially water-free atmosphere, such as a dry nitrogen atmosphere.

According to some variations, the materials introduced into the reactor in the method of embodiments of the invention consist essentially, or consist, of the compounds of formulas II and III, the solvent and the Lewis acid.

According to other variations, the materials introduced into the reactor in the method of embodiments of the invention additionally comprise one or more additives for increasing the solubility of Lewis acid complexes. These additives may notably be selected from Lewis bases such as diphenylsulfone, carboxylic acids, ethers and inorganic salts such as LiCI, NaCI, KCI, CaCL and MgCL, as well as mixtures thereof.

According to the invention, a starting mixture comprising the first reactant in a solvent, preferably in a separate solvent, is provided as a first step. In specific embodiments, the solvent is introduced prior to the first reactant into the reactor.

As a second step, the second reactant is added to the starting mixture.

The Lewis acid can be mixed to the starting mixture at the first step, or added to the starting mixture at the second step, or even part of the Lewis acid can be mixed to the starting mixture at the first step and part of the Lewis acid can be added to the starting mixture at the second step.

This two-step addition of the two reactants enable to obtain 1 ,4-bis(4-phenoxybenzoyl)benzene with a high purity and a high yield, in an efficient way. In particular, it enables to avoid any prior contacting time between the two reactants as in the methods of the prior art, in which the two reactants have to be first mixed together for several hours and heated before adding the second reactant. It also enables to reduce the production of unwanted by-products such as 4-(4-phenoxybenzoyl)benzoic acid or 4-(4-phenoxybenzoyl)benzoic acid ester.

In some embodiments, terephthaloyl chloride can be the second reactant. In these embodiments the diphenyl ether is therefore the first reactant, which is mixed in the solvent to make the starting mixture. The advantage to add terephthaloyl chloride as the second reactant to the starting mixture is that it enables to reduce the excess amount of the Lewis acid compared to the amount of terephthaloyl chloride introduced into the reactor. It also enables to reduce the excess amount of diphenyl ether compared to the amount of terephthaloyl chloride introduced into the reactor. Terephthaloyl chloride can be added in its solid form or in its liquid form. Alternatively, it can also be added as a suspension or a colloid, namely as a heterogeneous mixture of solid particles of terephthaloyl chloride in a solvent. The solvent for the suspension/colloid is advantageously the abovementioned reaction solvent. Alternatively, it can also be added as a solution, namely as a homogeneous mixture of liquid terephthaloyl chloride in a solvent. The solvent for the solution is preferably the abovementioned reaction solvent.

In some embodiments, terephthaloyl chloride can be the first reactant. In these embodiments, the diphenyl ether is therefore the second reactant, which is added to the starting mixture. The advantage to use the diphenyl ether as the second reactant is that it has a relatively low fusion temperature (26,9°C) and can therefore be added in its liquid form at a temperature which is close to the ambient temperature. Hence, the diphenyl ether can be added very precisely to the starting mixture. Alternatively, the diphenyl ether can be added to the starting mixture as a solution in a solvent, preferably in the abovementioned solvent. In less preferred embodiments, diphenyl ether is added as a solid, or as a suspension or a colloid in a solvent, preferably in the abovementioned reaction solvent. In addition, the advantage to use the diphenyl ether as the second reactant is that the diphenyl ether is less prone to hydrolysis during the step of addition to the starting mixture than the terephthaloyl chloride.

The Lewis acid can be a solid. In some variations, the Lewis acid can be in a particulate form, such as in the form of granules (having, e.g., a Dv80 of more than 1 mm) or in the form of a powder (having, e.g., a Dv80 of less than 1 mm, and preferably a Dv50 of less than 0.5 mm). Dv80 and Dv50 are respectively the particle sizes at the 80th and 50th percentiles (in volume) of the cumulative size distribution of the Lewis acid particles. These parameters may be determined by sieving. Alternatively, the Lewis acid can also be added as a suspension or a colloid in a solvent. The solvent for the suspension/colloid is advantageously the abovementioned reaction solvent. Alternatively, it can also be added as a solution in a solvent. The solvent for the solution is preferably the abovementioned reaction solvent.

Lewis acids which may be used include, for example, aluminum trichloride, aluminum tribromide, antimony pentachloride, antimony pentafluoride, indium trichloride, gallium trichloride, boron trichloride, boron trifluoride, zinc chloride, ferric chloride, stannic chloride, titanium tetrachloride, and molybdenum pentachloride. Aluminum trichloride, boron trichloride, aluminum tribromide, titanium tetrachloride, antimony pentachloride, ferric chloride, gallium trichloride, and molybdenum pentachloride are preferred. Aluminum trichloride is particularly preferred.

In some embodiments, the Lewis acid can be mixed to the starting mixture before adding the second reactant to the starting mixture. In particular, when the first reactant is terephthaloyl chloride, the Lewis acid can be mixed to the starting mixture before adding the diphenyl ether to the starting mixture.

In some embodiments, the Lewis acid can be mixed with the second reactant and added together to the starting mixture. In particular, when the second reactant is terephthaloyl chloride, the Lewis acid can be mixed with terephthaloyl chloride and added together to the starting mixture.

In some embodiments, the Lewis acid can be partly mixed to the starting mixture before adding the second reactant to the starting mixture and, partly mixed with the second reactant and added together to the starting mixture.

In some particular embodiments, the weight concentrations and weight ratios of the reactants and of the catalyst are as follows: the concentration of terephthaloyl chloride (relative to the sum of solvent, terephthaloyl chloride, diphenyl ether and Lewis acid introduced into the reactor) is from 3 to 12%, preferably from 5 to 10%;

- the concentration of diphenyl ether (relative to the sum of solvent, terephthaloyl chloride, diphenyl ether and Lewis acid introduced into the reactor) is from 5 to 35%, preferably from 12 to 25%;

- the concentration of Lewis acid (relative to the sum of solvent, terephthaloyl chloride, diphenyl ether and Lewis acid introduced into the reactor) is from 4 to 30%, preferably from 10 to 25%;

- the weight ratio of terephthaloyl chloride to diphenyl ether introduced into the reactor is from 0.2 to 0.6, preferably from 0.3 to 0.5;

- the weight ratio of Lewis acid to terephthaloyl chloride plus diphenyl ether introduced into the reactor is from 0.2 to 0.9, preferably from 0.3 to 0.7.

The addition of the second reactant is preferably performed progressively, over a period of time which can advantageously range from 5 to 600 minutes, preferably from 30 to 300 minutes.

The addition can be performed continuously or with one or more interruptions. If it is performed continuously, it can be conducted at a constant rate of addition. Alternatively, the rate of addition can vary over time.

The starting mixture may preferably be agitated during at least part of the reaction step. Thus, the reactor is preferably provided with an agitation device such as a mechanical stirrer (which may, e.g., comprise one or more impellers) or a recirculation loop with a pump.

Preferably, the starting mixture may be agitated owing to the agitation device during the addition of the second reactant.

Once the addition of the second reactant to the starting mixture is complete, the reaction step may optionally comprise a step of maintaining the starting mixture, preferably under agitation, for a certain time, in order to complete the reaction to the desired degree. Preferably, the mixture is maintained from 0 to 600 min, more preferably from 5 to 180 min.

Once the reaction is completed to the desired degree, the starting mixture becomes designated as a product mixture.

The end of the reaction step corresponds to the beginning of the next step in the method, which is usually a purification step, as described in more detail below.

During the reaction step, 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is initially produced as a dissolved species, the concentration of which progressively increases.

In preferred embodiments, at some point of time during the reaction step, the concentration of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex exceeds the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex. In other terms, in these embodiments, the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is maintained in a supersaturated state during at least part of the step of reacting terephthaloyl chloride with diphenyl ether.

This saturation limit depends on the conditions of the starting mixture in real time and may vary during the reaction step. It depends on the temperature of the starting mixture, the nature of the solvent and the amount of Lewis-acid.

The 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is said to be in a supersaturated state when it is dissolved in the starting mixture at a concentration exceeding the saturation limit. The supersaturated state is a metastable state. Therefore, the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid

complex in a supersaturated state is able to suddenly precipitate if a nucleating agent ( e.g ., solid particles), such as hydrolyzed terephthaloyl chloride, is present in the starting mixture.

By way of convention, in the present application the concentration of the

1 .4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex is indicated by the weight concentration of 1 ,4-bis(4-phenoxybenzoyl)benzene in the solvent. The same applies to the saturation limit

CLAIMS

1. A method for manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene, comprising:

- providing a solvent, a Lewis acid, a first reactant and a second reactant,

wherein the first reactant and the second reactant are respectively terephthaloyl chloride and diphenyl ether, or reversely;

wherein the terephthaloyl chloride is of a purity grade such that, 10 minutes after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 100 NTU;

- mixing the first reactant in the solvent to make a starting mixture; and,

- adding the second reactant to the starting mixture; wherein the Lewis acid is mixed, at least partly, to the starting mixture before adding the second reactant to the starting mixture, and/or

wherein the Lewis acid is mixed, at least partly, with the second reactant and added together to the starting mixture; so as to obtain a product mixture comprising a 1 ,4-bis(4- phenoxybenzoyl)benzene-Lewis acid complex.

2. The method of claim 1 , wherein the terephthaloyl chloride is of a purity grade such that:

- 10 minutes after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 200 NTU, preferably of less than 100 NTU, more preferably of less than 50 NTU, and most preferably of less than 10 NTU;

- preferably, 10 hours after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less 100 NTU, even more preferably of less than 50 NTU and most preferably of less than 10 NTU; and

- more preferably, 24 hours after introducing it at a reference concentration of 6.5 wt.% into ortho-dichlorobenzene containing less than 100 ppm by weight of water, at a temperature of 20°C, a solution is obtained having a turbidity of less than 100 NTU, even more preferably of less than 50 NTU and most preferably of less than 10 NTU.

3. The method of claim 1 or claim 2, wherein the terephthaloyl chloride is kept in a sealed container without contact with ambient air before use.

4. The method of any one of claims 1 to 3, wherein the diphenyl ether and solvent, in combination, contain less than 500 ppm by weight of water, advantageously less than 250 ppm by weight of water, preferably less than 150 ppm by weight of water, more preferably less than 100 ppm by weight of water, and most preferably less than 50 ppm by weight of water.

5. The method of any one of claims 1 to 4, wherein the diphenyl ether and solvent, in combination, contain from 1 to 250 ppm by weight of water, preferably from 2 to 200 ppm by weight of water, more preferably from 3 to 150 ppm by weight of water, even more preferably from 4 to 100 ppm by weight of water and most preferably from 5 to 50 ppm by weight of water.

6. The method of any one of claims 1 to 5, comprising a step of drying the solvent and/or the diphenyl ether before use, preferably by distillation or by contacting with a molecular sieve or with a dehydrating agent.

7. The method of any one of claims 1 to 6, wherein the 1 ,4-bis(4- phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration in the solvent which is higher than the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex during at least part of the reaction of the terephthaloyl chloride with the diphenyl ether.

8. The method of any one of claims 1 to 7, wherein the 1 ,4-bis(4- phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration which is higher by at least 5 %, preferably by at least 10 %, more preferably by at least 20 %, than the saturation limit of the 1 ,4-bis(4-phenoxybenzoyl)benzene-Lewis acid complex, during part of the reaction of the terephthaloyl chloride with the diphenyl ether.

9. The method of any one of claims 1 to 8, wherein the 1 ,4-bis(4- phenoxybenzoyl)benzene-Lewis acid complex is dissolved in the solvent at a 1 ,4-bis(4-phenoxybenzoyl)benzene weight concentration of more than 5 wt.%, preferably more than 10 wt.%, more preferably more than 15 wt.%, and most preferably more than 30 wt.%, during part of the reaction of the terephthaloyl chloride with the diphenyl ether.

10. The method of any one of claims 1 to 9, wherein the Lewis acid is chosen among the list consisting of: aluminum trichloride, aluminum tribromide, antimony pentachloride, antimony pentafluoride, indium trichloride, gallium trichloride, boron trichloride, boron trifluoride, zinc chloride, ferric chloride, stannic chloride, titanium tetrachloride, and molybdenum pentachloride; preferably, the Lewis acid is chosen among the list consisting of: aluminum trichloride, boron trichloride, aluminum tribromide, titanium tetrachloride, antimony pentachloride, ferric chloride, gallium trichloride, and molybdenum pentachloride; even more preferably the Lewis acid is aluminum trichloride.

11. The method of any one of claims 1 to 10, wherein the Lewis acid, the first reactant or the second reactant plays the role of the solvent.

12. The method of any one of claims 1 to 10, wherein the solvent is ortho-dichlorobenzene.

13. The method of any one of claims 1 to 12, wherein the second reactant is terephthaloyl chloride and,

wherein the Lewis acid is mixed with terephthaloyl chloride and added together to the starting mixture.

14. The method of any one of claims 1 to 12, wherein the first reactant is terephthaloyl chloride and,

wherein the Lewis acid is mixed with the starting mixture before adding the diphenyl ether to the starting mixture.

15. A method of making a polyaryl ether ketone polymer, comprising:

- manufacturing 1 ,4-bis(4-phenoxybenzoyl)benzene according to the method of any one of claims 1 to 14;

- reacting said 1 ,4-bis(4-phenoxybenzoyl)benzene with at least one difunctional aromatic acyl chloride.