NO175096B - Process for the preparation of 1,4-bis (4-phenoxybenzoyl) benzene with certain metal-containing catalysts - Google Patents

Description

The background of the invention

The invention relates to a method for the production of 1,4-bis(4-phenoxybenzoyl)benzene in a homogeneous or heterogeneous system, in the presence of certain metal salt catalysts.

1,4-bis(4-phenoxybenzoyl)benzene (hereinafter sometimes referred to as BPBB), which is an important intermediate in the production of polyether ketone resins, is currently produced industrially by reacting 1,4-benzenedicarbonyl chloride with diphenyl ether in the presence of a Friedel-Crafts catalyst, usually aluminum chloride, which is used in an amount of at least 3 mol per moles of 1,4-benzenedicarbonyl chloride. Polyether ketones are a well-known generic class of commercially available resins, which include true polyether ketones, poly(ether-ether-ketones), poly(ether-ketone-ketones) and mixed copolymers having segments of both the former type and the latter type. Diphenyl ether is normally used in a significant excess to minimize formation of higher oligomers. Normally, the reaction is carried out in such a solvent as, for example, 1,2-dichlorobenzene at a temperature of approximately 0 °C. After the reaction is complete, methanol is added to precipitate the product and remove the catalyst from it. The product is filtered off, washed repeatedly with methanol and recrystallized from N,N-dimethylacetamide or 1,2-dichlorobenzene.

The use of aluminum chloride presents various shortcomings. The recovered aluminum chloride cannot be reused, and this creates a waste disposal problem and increases the cost of operation. Furthermore, aluminum chloride does not have a high para,para isomer selectivity, so that it tends to also give a significant proportion of the ortho,para isomer, i.e. [1-(2-phenoxy),4-(4-phenoxy)] dibenzoylbenzene. Due to extensive purification that requires repeated filtrations, long recovery times are necessary.

BPBB can also be prepared by reacting 1,4-benzenedicarbonyl chloride with an excess of diphenyl ether at 190-258 °C. in the presence of hydrogen-exchanged zeolite catalysts which are highly para,para-isomer selective, as described in US Patent Application No. 07/218941 to Corbin et al., filed July 14, 1988, which is now patent. Although the invention described and claimed in the approved application constitutes a significant advantage in relation to the current industrial method described above, it also has certain disadvantages. It requires a very large excess of diphenyl ether as well as a significant amount of zeolite catalyst. The high ratio between diphenyl ether and 1,4-benzenedicarbonyl chloride and the large amount of catalyst make operation very expensive. Furthermore, the hydrogen yielded zeolite must either be regenerated or discarded, which in turn increases the production cost.

It is therefore desirable to be able to prepare BPBB in an isomer-selective, simple operation requiring no solvent, precursor with a smaller excess of diphenyl ether and with a significantly smaller amount of catalyst. Furthermore, it would be highly desirable to be able to either reuse the catalyst without regeneration or dispose of it without great expense.

Summary of the invention

According to the invention, a method for the production of BPBB has now been provided, where the method comprises bringing diphenyl ether into contact with 1,4-benzenedicarbonyl chloride for a period of 60 to 360 min at a temperature of 220-258 °C in a respective molar ratio of 5:1 to 25:1 in the presence of at least one catalyst selected from the group consisting of iron (II) chloride (ferrochloride), iron (II) sulfate (ferrous sulfate), gallium (II) sulfate and indium (III) sulfate without carrier, and iron (II) chloride, iron (II) sulfate, gallium (III) sulfate, indium (III) sulfate and iron (III) chloride (ferric chloride) on an inert carrier, and where the molar ratio between 1 ,4-benzenedicarbonyl chloride and the catalyst is 10:1 to 1000:1, and recover the BPBB product by separating it from both excess diphenyl ether and the catalyst.

Detailed description of the invention

The basic reaction involved in the method according to the invention is shown in the following reaction equation:

The starting materials for this turnover are well known and readily available.

1,4-benzenedicarbonyl chloride, also known as terephthalyl chloride, can be made from terephthalic acid by any suitable known reaction, e.g. with phosphorus pentachloride, phosphorus trichloride or thionyl chloride.

1,4-benzenedicarbonyl chloride is also commercially available, e.g. from E.I. Du Pont de Nemours and Company.

Diphenyl ether is commercially available, i.a. from Dow Chemical Company.

The catalysts are available from several sources, including Alfa Division of Morton Thiokol Co. and Aldrich Chemicals. They can be used in a homogeneous system as they dissolve to a sufficient extent in the reaction mixture at the reaction temperature, or in a heterogeneous system when they are deposited on an inert carrier material. Suitable carrier materials include e.g. silica, alumina and carbon.

In the practical operation of the method according to the invention, the reactants and the catalyst are filled in a reactor, and the temperature is increased to 220-258 °C. Although an excess of diphenyl ether is required, it is preferred to keep the molar ratio between diphenyl ether and 1,4-benzenedicarbonyl chloride within the range of 6-10:1. The preferred molar ratio of 1,4-benzenedicarbonyl chloride to catalyst is 50 to 300. The preferred reaction temperature range is 240-258°C. Within this temperature range, the preferred reaction time is 180-360 min. The most preferred time and temperature conditions are approx.

5 hours at 250 °C. The most preferred molar ratio between diphenyl ether and 1,4-benzenedicarbonyl chloride is approx. 8, and the most preferred molar ratio between 1,4-benzenedicarbonyl chloride and catalyst is approx. 200. The preferred catalyst which does not

is on a support, is ferrochloride.

Although many metal compounds have been found to catalyze the condensation of diphenyl ether with 1,4-benzenedicarbonyl chloride, only BPBB made in the presence of the catalysts listed in the summary gave a polyether ketone that was heat stable.

If the process temperature is too low, the starting materials will generally be converted mainly into adducts of

1 mole of diphenyl ether and 1 mole of 1,4-benzenedicarbonyl chloride; conversion to the desired product, BPBB, will be minimal. If the temperature is too high (if the reaction is carried out under pressure), conversion can also be reduced due to large amounts of by-products and decomposition of 1,4-benzenedicarbonyl chloride. If the molar ratio between diphenyl ether and 1,4-benzenedicarbonyl chloride is too low, the conversion to BPBB will be

low; if it is too high, the benefits of having a high BPBB product concentration in the reaction mixture will not be realized. If the molar ratio between 1,4-benzenedicarbonyl chloride and catalyst is too high, the reaction is too slow; if it is too low, the separation of BPBB from the catalyst may be more difficult.

When the catalyst is in solution in a homogeneous system, it is not recovered but discarded; however, a supported catalyst used in a heterogeneous system can be recovered and reused without the need for regeneration. When the catalyst can be reused, a further advantage is realized. The supported catalyst can be easily separated by filtration or otherwise from the hot, liquid reaction mixture. The unsupported catalyst that contaminates the solid BPBB product can be easily removed from it by washing with a suitable solvent, such as e.g. methanol.

BPBB which crystallizes from the solution in diphenyl ether after cooling (e.g. to 30-50 °C) must in all cases be washed with a solvent such as methanol to remove diphenyl ether and any adduct of 1 mol diphenyl ether and 1 mol 1, 4-benzenedicarbonyl chloride which may have crystallized during cooling. Other solvents that are suitable for this purpose are, among other things, tetrahydrofuran, isopropyl alcohol and acetone. If desired, BPBB can be further purified by recrystallization from such solvents as e.g. N,N-dimethylacetamide and 1,2-dichlorobenzene. The solvent-washed or recrystallized BPBB can be used in the final step in the preparation of a polyether ketone by condensation with additional 1,4-benzenedicarbonyl chloride (or another dicarboxylic acid dichloride) in a manner known in the art.

Surplus diphenyl ether recovered from the BPBB production by the method according to the invention can be reused several times without purification. When purification is thought to be advisable, this is most conveniently done by distillation at reduced pressure.

Although the above description relates to a batch method according to the invention, the method can be adapted to a continuous operation where the critical variable quantities that must be controlled are the molar ratio between 1,4-benzenedicarbonyl chloride and catalyst, the molar ratio between diphenyl ether and 1,4-benzenedicarbonyl chloride , the temperature and the residence time. Various routine operations can be modified in both the batch process and the continuous process to achieve the greatest operating efficiency; e.g. separation of solids from liquids can be achieved not only by filtration, but also by decantation or centrifugation, depending on what is most convenient, e.g. based on consideration of time, energy needs and equipment availability.

The invention will now be illustrated by means of representative examples for certain preferred embodiments. In all examples, the conversion of 1,4-benzenedicarbonyl chloride to BPBB was calculated as follows:

Any partial reaction product comprising one molecule of each reactant that may have been formed as a by-product was disregarded. All catalysts were used as received.

Example 1

Various metal compounds were used to catalyze BPBB synthesis. Diphenyl ether (134 g, 0.787 mol) was mixed with 20 g (0.099 mol) of 1,4-benzenedicarbonyl chloride and 0.5 g of the metal compound in a reactor. The mixture was heated to 250 °C under nitrogen flow and held at this temperature for 5 hours. 187 g of diphenyl ether at 80 °C was added to the reactor to cool the reaction mixture to approx. 180 °C. The solution was filtered at approx. 180 "C and allowed to cool. The product was filtered at 50 °C, washed with methanol and dried in The results of these experiments are summarized in Table I below. The following column designations are used:

A = metal compound

B = conversion to BPBB

C = a/b melting peaks by differential scanning calorimetry, °C, with a heating rate of

20 <0>C/min in a nitrogen atmosphere, where "a" and "b" are the melting peaks at the first heating and remelting; a minus sign means very impure material, with shoulders and/or secondary peaks. When the melting and remelting temperatures are only a few degrees apart, the material is reasonably heat-stable and therefore usually reasonably pure, but this is not the only purity criterion. D = melt stability of polymer made from BPBB, where "+" = melt stable; "-" = melt unstable; "0" = not determined due to lack of purity or low yield.

Example 2

Ferric chloride on silica catalyst, Alfa 10677 from Morton Thiokol, was tested in a repetitive experiment. The same catalyst was used in all experiments without any regeneration. Between experiments, the catalyst was stored in a vacuum oven at 110 °C under nitrogen flushing. This catalyst, 1.5 g, was mixed with 267.5 g (1.572 mol) of diphenyl ether and 40 g (0.197 mol) of 1,4-benzenedicarbonyl chloride in each trial. The mixture was heated under nitrogen to 250 °C and held at this temperature for 5 hours. Diphenyl ether, 374.5 g, at 80°C was added to the reactor to cool the reaction mixture to approx. 180 °C. The solution was filtered at about 180 °C and allowed to cool; crystals of BPBB began to precipitate at about 140 °C. The product was filtered at 50 °C, washed with methanol and dried. The conversions to BPBB are indicated below.

This example shows that a supported iron(III) catalyst can be reused several times without regeneration, retaining its catalytic activity.

Example 3

Diphenyl ether recovered from the first run in Example 1 was reused without purification, except that it was refiltered at 30°C one day after the run. This recovered diphenyl ether (134 g, 0.787 mol) was mixed with 20 g (0.099 mol) of 1,4-benzenedicarbonyl chloride and 0.75 g of freshly prepared ferric chloride on silica catalyst support (Alfa 10677 from Morton Thiokol) in a reactor . The mixture was heated in the reactor to 250 °C under nitrogen purging and held at 250 °C for 5 hours. Recovered diphenyl ether, 187 g, at 80 °C was added to cool the reaction mixture to about 180 °C. The solution was filtered at about 180 "C and allowed to cool; the crystals of BPBB began to precipitate at ca. 140 °C. The product was filtered at 50°C, washed with methanol and dried. It weighed 33.10 g for a conversion of 71.4%. Very small amounts of impurities were found by differential scanning calorimetry. This example shows that diphenyl ether can be reused without redistillation.

Example 4

This example illustrates four different BPBB purification procedures. Iron(III) chloride on silica catalyst. Alfa 10677 from Morton Thiokol, was dried overnight in a vacuum oven at 110 "C under nitrogen purging. 3 g of this catalyst was mixed with 535 g (3.143 mol) of diphenyl ether and 80 g (0.394 mol) of 1,4-benzenedicarbonyl chloride in a reactor The mixture was heated to 50°C and held at this temperature for 30 min under a strong nitrogen purge to remove any residual oxygen from the system. The mixture was then heated under a low nitrogen purge to 250 °C and held at this temperature for 5 hours. A total of 749 g (4.401 mol) of diphenyl ether at 80 °C was added to cool the reaction mixture to approx. 180 °C. The solution was filtered at approx. 180 °C and allowed to cool; the crystals of BPBB began to precipitate at ca. 140 °C. The product was filtered off from diphenyl ether at approx. 40 °C and was divided into four portions which were prepared as follows: I. Washed twice with 350 ml of methanol with stirring, 30 min at each wash, followed by filtration. Dried overnight in a vacuum oven at 110°C, the product weighed 35.8 g. Melting peaks a/b (determined as in column c of Table I) 213/206. II. Washed twice with 350 ml tetrahydrofuran with stirring, 30 min each wash, followed by filtration. Dried as above, the product weighed 32.0 g. Melting peaks a/b 215/206. III. Washed twice with 350 ml of methanol with stirring, 30 min at each wash, followed by filtration. Recrystallized from 457 g of 1,2-dichlorobenzene. Washed twice with 350 ml of methanol with stirring, 30 min at each wash, followed by filtration. Dried as above, the product weighed

36.7 g. Melting peaks a/b 214/206.

IV. Washed twice with 350 ml tetrahydrofuran with stirring, 30 min each wash, followed by filtration. Recrystallized from 457 g of 1,2-dichlorobenzene. Washed twice with 350 ml tetrahydrofuran with stirring, 30 min each wash, followed by filtration. The dry product weighed 26.8 g. Melting peaks a/b 214/206.

The total weight of purified BPBB was thus 131.3 g, for a conversion of 70.8%.

The efficiency of BPBB made in the presence of different catalysts was determined as follows: BPBB was chain-extended with 1,3-benzenedicarbonyl chloride and 1,4-benzenedicarbonyl chloride to aromatic poly(ether-ketone-ketone) in the presence of a

"capping" agent, excess aluminum chloride as catalyst and 1,2^-dichlorobenzene as solvent. After the synthesis, the polymer was filtered from the solvent, poured into methanol to eliminate the complexation with aluminum chloride, washed with methanol to extract residual aluminum and dried. The melt stability was tested with an extrusion plastometer. The following procedure was used in the polymerization experiments.

BPBB, 23.53 g (0.050 mol), 29.32 g (0.22 mol) of aluminum chloride and 313 g of 1,2-dichlorobenzene were charged into a 1 liter magnetically stirred Erlenmeyer flask which was then sealed. Separately, 3.54 g (0.017 mol) of 1,4-benzenedicarbonyl chloride, 5.87 g (0.029 mol) of 1,3-benzenedicarbonyl chloride, 0.34 g (0.0024 mol) of benzenecarbonyl chloride, 13.78 g (0.103 mol) of aluminum chloride and 313 g of 1,2-dichlorobenzene filled into a 500 ml, magnetically stirred Erlenmeyer flask which was then closed. Each mixture was stirred at room temperature for 20 min and then cooled to 0 °C in a water and acetone bath. At 0 °C, the contents of the 500 ml flask were transferred to the 1 liter flask. The 500 ml flask was washed with 39 g of 1,2-dichlorobenzene, and the washing solution was transferred to the 1 liter flask which was then capped. The combined mixture was held at 0°C for 30 min and then transferred to a 1-liter resin kettle with a heat jacket and equipped with an agitator and a nitrogen purge. The boiler was heated with saturated steam, so that the temperature in the reactor reached 100 "Ci during approx.

10 minutes Solids began to precipitate at approx. 50 °C, which indicates the formation of polymer. After 1 hour at 100 °C, the boiler was cooled with running water to 25 °C. The slurry was filtered to recover the produced complex of polymer and aluminum chloride. The polymer was poured into a 1 liter beaker containing 500 ml of methanol at -15°C to eliminate complexation between the polymer and aluminum chloride. After stirring for 30 minutes, the polymer was filtered off and washed three times for 30 minutes with 500 ml of methanol in a stirred 1-liter beaker. The polymer was then washed for 45 min with 800 ml of boiling water, filtered and dried in a vacuum oven for 16 h at 110 °C.

Melt flow rate was determined to evaluate the melt stability of the polymer and also to give an indication of its molecular weight. The flow rate was determined according to ASTM D 1238-85 in an extrusion plastometer with a load of 8.2 kg. A flow rate below 10 g/10 min indicates that the molecular weight of the polymer is so high that the polymer is difficult to process in the melt due to its high viscosity. A flow rate below 10 g/10 min means a number-average molecular weight of approx. 12000. A flow rate above 200 g/10 min means that the molecular weight is too low for most applications due to the low modulus of elasticity and tensile strength. At a flow rate above 200 g/10 min, the number average molecular weight is approx. 5000. Normally, the most useful number average molecular weight range for this type of polymer is approx. 7000-9000.

The molecular weight was determined by adding 0.025 g of polymer to 25 ml of a mixture of equal weights of phenol and 1,2,4-trichlorobenzene, heating the mixture at 175 °C to dissolve the polymer, filtering the solution at 115 °C and spraying it into a gas chromatograph operated at 115 °C and calibrated with a solution of polystyrene of known molecular weight in the same solvent mixture.

Melt stability was evaluated based on the physical appearance of the extrudate from the plastometer. A smooth extrudate with bubbles means that the polymer is melt stable; an extrudate that is uneven and/or full of bubbles means that the polymer is not heat stable.

Example 5

The BPBB made in Example 1 in the experiments catalyzed by ferric chloride tetrahydrate and ferric sulfate heptahydrate was recrystallized in each case by dissolving 32 g of BPBB in 457 g of 1,2-dichlorobenzene at 160 °C and filter while hot, cool the filtrate to 30 °C and recover BPBB by filtration. The BPBB was then washed twice for 30 min with 350 ml of methanol, dried in a vacuum oven at 110 °C and ground in a mixer. BPBB was chain extended as described above. The following results were obtained:

The extrudates of both polymers were smooth with bubbles, indicating melt stability. The extrudates of the polymers from BPBB catalyzed by means of iron (II) chloride tetrahydrate and iron (II) sulphate heptahydrate were respectively light brown and dark brown.

Comparison example 1

A mixture of 53.5 g of diphenyl ether with 0.4 g of anhydrous ferric chloride in a tightly closed Erlenmeyer was stirred overnight and then filtered. The ferric chloride that remained on the filter was dried and weighed. Based on weight loss, 0.0005 mol (0.078 g) had

ferric chloride has been dissolved.

Half of the diphenyl ether and ferric chloride filtrate was mixed with 107.3 g of additional diphenyl ether and 20 g (0.099 mol) of 1,4-benzenedicarbonyl chloride in a reactor. The mixture was heated to 250 °C under nitrogen purging. The color changed from black to red and finally to dark brown as the reaction proceeded at this temperature for 6 hours. Diphenyl ether at 80 °C, 187 g, was added to the reactor to cool the reaction mixture to approx. 180 °C. The solution was filtered while hot and allowed to cool. The product was filtered at 30°C, washed with methanol and dried: It weighed 35.70 g for a conversion of 77.0%. Small amounts of the ortho,para isomer were detected by proton nuclear magnetic resonance.

Comparison example 2

Chain extension was the same as in Example 5, except that the starting BPBB was the same as in Comparative Example 1. Flow rate in the extrusion plastometer was 104 g/10 min. The extrudate was black and full of bubbles. This extrudate with high flow rate and bubbling indicates that the starting BPBB was not of satisfactory purity and that the polymer was not stable in the melt. From this example, it is concluded that although unsupported ferric chloride catalyzes the formation of BPBB to a high conversion, it nevertheless does not provide pure material suitable for chain extension to a poly(ether-ketone-ketone).

Comparison example 3

BPBB according to Example 1 catalyzed by means of gallium(III) chloride was recrystallized by dissolving 32 g of BPBB in 375 g of N,N-dimethylacetamide at 160 °C and filtering while hot, then cooling the filtrate to 30 °C and extracting -ning of BPBB by filtration. The recrystallized material was washed twice for 30 min with 350 ml of methanol, dried in a vacuum oven at 110 °C and ground in a mixer. This purified BPBB was chain extended as described above, except that the 0.34 g (0.0024 mol) of benzenecarbonyl chloride was replaced with 0.42 g (0.0020 mol) of 3,5-dichlorobenzenedicarbonyl chloride. The extrudate from the extrusion plastometer was black, full of bubbles and very brittle. The flow rate was 11 g/10 min. This example shows that gallium(III) chloride is not a suitable catalyst for the production of polymerization grade BPBB.

Example 6

The same as Example 5, except that the BPBB used was the same as in Example 1, catalyzed either with gallium(III) sulphate or with indium(III) sulphate hydrate. The results were as follows:

The extrudates of both polymers were very smooth without bubbles, indicating adequate melt stability. The color was brown in both cases.

Example 7

Each of the four BPBB portions from Example 4 was chain extended as described above. The flow rate and appearance of the respective polymers are reproduced below:

This example shows that recrystallization of BPBB prepared with supported ferric chloride gives a material of satisfactory purity for further condensation to a poly-(ether-ketone-ketone).

Comparison example 4

BPBB was synthesized from diphenyl ether and 1,4-benzenedicarbonyl chloride in 1,2-dichlorobenzene in the presence of excess aluminum chloride, as is known in the art. It was washed several times with methanol and dried. A total of 1.8 kg of dry BPBB was recrystallized by dissolving it in 17 kg of N,N-dimethylacetamide at 160 °C, filtering while hot, cooling to 30 °C and recovering BPBB by filtration. This material was washed with methanol, dried in a vacuum oven and ground in a blender This BPBB was found to be 99.9% pure as determined by differential scanning calorimetry (first melt and remelt peaked at 215 °C), UV/Vis spectrophotometry and proton nuclear magnetic resonance. BPBB was polymerized by the method described above to a melt-stable material having an extrusion plastometer flow rate of 26 g/10 min. The color of the extrudate was amber. This comparative example shows that BPBB polymers made from BPBB prepared in presence of the catalysts of the present invention provides a poly(ether-ketone-ketone) which, although darker, has approximately the same molecular weight and melt stability as the poly(ether-ketone-ketone) produced from BPBB of high purity prepared in a manner known in the art.

Claims (10)

1. Process for the production of 1, 4-bis(4-phenoxy-benzoyl)benzene, characterized in that diphenyl ether is brought into contact with 1,4-benzenedicarbonyl chloride for a period of 60 to 360 min, at a temperature of 220-258 °C, in respective molar ratios of 5:1 to 25:1 in the presence of at least one selected catalyst from the group consisting of iron (II) chloride (ferrochloride), iron (II) sulfate (ferrosulfate), gallium (III) sulfate and indium (III) sulfate not on a support, and iron (II) -chloride, iron (II) sulfate, gallium (III) sulfate, indium (III) sulfate and iron (III) chloride (ferric chloride) on an inert support; and wherein the molar ratio of 1,4-benzenedicarbonyl chloride to the catalyst is 10:1 to 1000:1, and the BPBB product is recovered by separating it from both excess diphenyl ether and from the catalyst. 2. Method according to claim 1, characterized in that the reaction temperature is 240-258 °C. 3. Method according to claim 2, characterized in that the molar ratio between diphenyl ether and 1,4-benzenedicarbonyl chloride is 6-10:1. 4. Method according to claim 2, characterized in that the reaction time is 180-360 min. 5. Method according to claim 4, characterized in that the reaction is carried out for approx. 5 hours at approx. 250 °C. 6. Method according to claim 1, characterized in that the catalyst is an iron (II) compound which is not on a support. 7. Method according to claim 6, characterized in that the iron (II) compound is ferric chloride. 8. Method according to claim 1, characterized in that the catalyst is an iron, gallium or indium compound on an inert carrier. 9. Method according to claim 8, characterized in that the catalyst is ferric chloride on an inert carrier. 10. Method according to claim 9, characterized in that the inert carrier is silica.