BE715201A - - Google Patents

Description

  

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  Process for preparing 2-hydroxyalkyl esters of aromatic polycarboxylic acids.



   The present invention relates to an improved process for the preparation of 2-hydroxyalkyl esters of polycarboxylic aromatic acids, such as bis (2-hydroxyethyl) terephthalate which is an intermediate compound of interest for the synthesis of linear high molecular weight polyesters. .



   The reaction of aromatic dicarboxylic acids with various glycols gives linear polyesters which have valuable properties for the manufacture of films and fibers. The product of the reaction of terephthalic acid and a glycol chosen from those of formula HO (CH2) nOH, where n

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 is an integer from 2 to 10 is described in the United States patent
 EMI2.1
 cain nu2.645-319 from vfninrield et al.

   From an industrial point of view, the most interesting polymer of this class is p * ly (ethyl torephthalate: ze) which is commonly prepared by transesterification between ethylene glycol and terephtha.
 EMI2.2
 i: ncithyl late to give bis (2-hydroxyethyl) terephthalate monomer which can then be polymerized to poly (terephthalate <l. 'et: ly:

  1e) under reduced pressure. Other useful polymers of a similar nature are the products of the con-
 EMI2.3
 densification of ethylene glycol with mixtures of terephthalic acid and isophthalic acid.
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 Attempts have already been made to carry out the direct reaction of ethylene glycol and other glycols with aromatic dicarboxylic acids to directly obtain bis-glycol dicarboxylates which lend themselves to the subsequent condensation polymerization into the desired linear super polyesters.

   These procedures are difficult to carry out due to the low solu-
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 bility of: a.c., for example of terephthalic acid, in glycol and of the poor esterification rate that can be achieved, even in the presence of a large excess of
 EMI2.6
 glycol .. DQ plus ..;, during direct esterification the glycol invariably undergoes some self-condensation resulting in ether glycols which adversely affect the properties of fibers made of polyester. However, some progress has recently been made in this direction.
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  Linear polyesters, such as poly (toréphtcilate ü'éthy, ne), are obtained very easily by trr4rasestéxi'.ca tion. However, this method of manufacture has the drawback that the aromatic dicarboxylic acid must first be converted by an initial esterification into a dialkyl ester.
 EMI2.8
 of high purity which is the dimethyl ester in most cases. This ester is then subjected to transesterification.

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 yielding the desired bis-hydroxyethyl dicarboxylate intermediate, which is then polymerized to the desired super polyesters.

   This synthetic route was chosen because the available terephthalic acid is difficult to purify and because it is easier to prepare a pure alkyl ester for reaction with ethylene glycol. To be very effective, the trans esterification must be carried out in the presence of a large molar excess of glycol, which must then be separated from the ester monomer, for example by distillation, and collected in the state of purity for its preparation. recycling. In addition, aleool, for example methanol, which is a by-product of transesterification cannot be discarded, but must be collected and recycled to esterification for the whole process to be carried out efficiently. and economical.



   More recently, progress has been made in the synthesis of monomeric glycol terephthalates by the direct reaction of terephthalic acid with ethylene oxide in aqueous alkaline solution under a pressure equal to or greater than that of terephthalic acid. atmosphere. The process requires equipment resistant to the effects of pressure and a large excess of ethylene oxide. At atmospheric pressure, an excess of ethylene oxide of more than 100% is necessary for the reaction with terephthalic acid to be complete.

   A large fraction of the ethylene oxide undergoes self-condensation giving unwanted products, so that the excess of ethylene oxide. cannot be collected and recycled.



   More recently, a process has been developed (US Pat. No. 2,901,505), according to which a solution of an aromatic dicarboxylic acid in a solvent comprising a lower dialkyl-formamide is brought into contact with an almost stoichiometric amount of dicarboxylic acid. 'an alkylene oxide at a temperature of about 25 to 200 C to obtain a reaction product which

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 consists essentially of the beta-hydroxyalkyl ester of dicarboxylic acid. The high boiling solvent, for example, N, N-dimethyl-formamide, is then separated from the reaction mixture, thereby obtaining in excellent yield the desired crude ester which is the residue.

   The product can then be freed from impurities by conventional purification techniques. This process requires a long time for the reaction to be completed, and furthermore, the solvent is difficult to remove completely, because its boiling point is high.



   The object of the present invention is to provide an improved process for producing hydroxyalkyl esters of aromatic polyearboxylic acids in high yield and high conversion by means of the catalyst described in U.S. Patent Application No. 579,854 of September 16, 1966 to Katzakian and Contributors, which is in part a continuation of U.S. Patent Application No. 523,046 of January 26, 1966.



   It is also an object of the invention to provide an economical process for the preparation of monomeric glycol terephthalates by direct reaction of ethylene oxide and other alkylene oxides with terephthalic acid in an inert solvent, such as. ketones, aliphatic hydrocarbons, aromatic hydrocarbons, halogenated aliphatic hydrocarbons, halogenated aromatic hydrocarbons, nitriles, nitroalkanes, etc.



   Another object of the invention is to provide 2-hydroxyalkyl esters of polycarboxylic aromatic acids obtained by reacting these acids with alkylene oxides in a reaction solvent consisting of the recycled esters obtained.



   It also aims to provide a process

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 preparation of bis (2-hydroxyethyl) terephthalate allowing continuous mass production.



   The process of the invention is especially useful for the preparation of bis (2-hydroxyethyl) terephthalate monomer by reaction of ethylene oxide with terephthalic acid under pressure in the presence of a clarome-type catalyst. However, the invention is generally applicable to the synthesis of other alkyl esters of 1-terephthalic acid by means of other alkylene oxides. Alkylene oxides can have 2 to 10 carbon atoms. Specific examples of these alkylene oxides are ethylene oxide, propylene oxide, 1,2-butylene oxide, 2,3-butylene oxide, isobutylene oxide , 1,2-epoxypentane, 1,2-epoxyhexane, 2,3-epoxy-1-propanol, cyclohexane oxide, cyclopentane oxide etc.

   The alkylene oxide can have an aromatic substituent, as in the case of styrene oxide, etc. Other reactive-inert substituents in the system may also be present and this is for example the case with halogen atoms, as in the case of eplchlorohydrin, epibromohydrin etc.



   The process of the invention can be applied to the condensation of alkylene oxides with phthalic acids, and in particular terephthalic acid and isophthalic acid, in addition to their mixtures * Phthalic acids bearing as substituents one or more alkyl radicals suitable, for example 5-methyl-isophthalic acid (uvitic acid), methyl-terephthalic acid, t-butylphthalic acid, etc. However, for the purposes of the invention, the acids of most interest are those which give relatively insoluble linear polyesters with a high melting point.



   The invention applies in particular to the production of esters of phthalic acids / but also to the production of esters of other aromatic polycarboxylic acids,

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 such as trimesic acid, trimellitic acid, pyromellitic acid, naphthalene di-, tri-, or tetracarboxyli- acid. that, diphenyl di-, tri-, or tetracarboxylic acid, various alkylated polyearboxylic acids and polycarboxylic acids
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 boxyls derived from compounds of formula: // \\ - A- \ 0 / where A represents a bridge, for example of oxygen or sulfur or an N-R 'radical, where R' represents a methyl or ethyl radical , acetyl or higher acyl.

   The radical A can also be an alkylene bridge, for example methylene, ethylene or.



     (CH2) x, where x is an integer up to about 10. In addition, A can also be an alkylene ether radical, for example -OCH20-, -OCH2CH2O-, -OCH2CH2CH2O-, -OCH2- and OCH2CH2-.



   The process of the invention can be carried out in a number of ways, but under a specific set of suitable conditions the alkylene oxide, for example ethylene oxide, is contacted with phthalic acid under pressure in an autoclave. According to one embodiment, the phthalic acid can be presented in the form of a suspension of terephthalic acid in an inert liquid solvent having a boiling point of less than about 200 ° C. and preferably from 50 to. 150 C and formed by a lower alkyl ketone, an aliphatic hydrocarbon, an aromatic hydrocarbon or a chlorinated solvent. In this embodiment of the invention, methylisobu- is used. tyl ketone, toluene or xylene as the reaction medium.



   Other solvents can be used, such as acetone, methyl ethyl ketone, chlorobenzene, benzene, orthodichlorobenzene. acetonitrile, 2-nitropropane, ethylene dichloride (1,2-dichloroethane) etc. The solvents can be used in the substantially pure state or after modification by an addition in moderate proportions, for example from about 1 to 50% by volume, of other miscible solvents. In general, a quantity

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 from about 1 to 10 parts by weight of solvent is sufficient to at least partially dissolve 1 part by weight of the phthalic acid at the reaction temperature, but smaller amounts of solvent can be used and form a suspension of the phthalic acid. acid in the solvent.

   Larger amounts of the solvent can also be used, but the configurations are less economical.



   It has been found that the chromium catalyst allows the successful use of solvents in which the solubility of terephthalic acid or any other phthalic acid is normally at best. The possibility of carrying out the reaction quickly, both in suspension and in solution, makes it possible to use inexpensive polar or non-polar solvents, having valuable physical properties, facilitating the isolation of the product. The solvent can be selected from a wide class of compounds, the main consideration obviously being that the solvent should be inert and this point being understood, any compound which dissolves little or a lot of phthalic acid is suitable.



  Normally, the solvent is liquid at room temperature and preferably has a relatively low boiling point, facilitating its recovery. It should be noted that higher boiling point solvents are suitable, but their recovery may be more difficult.



   . The alkylene oxide used for the reaction can be added to the mixture of phthalic acid and the solvent, after which the complete mixture can be heated to the reaction temperature, but preferably the mixture of acacia and solvent is heated to the reaction temperature and the alkylene oxide is added thereto directly. In the case of ethylene oxide which is gaseous at room temperature and atmospheric pressure, the admission can be carried out directly under pressure in the solvent. Liquid alkylene oxides can

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 can be added directly to the reaction mixture or under pressure.

   Solid alkylene oxides, such as styrene oxide, can be melted or dissolved in additional suitable solvent and added directly to the reaction mixture.



   As indicated above, the use of an inert solvent together with a chromium catalyst provides good yields and a high purity product.



  However, the use of inert solvent increases installation and operating costs. Therefore, in a preferred embodiment, the number of compounds to be used is reduced and the solvents are eliminated. More specifically, by using the final molten ester as an inert solvent, the need for any other organic solvent as the reaction medium is eliminated.



   The process of the invention can be carried out for values of the molecular ratio falling within a wide range, but it has been found that in general the molecular ratio of the reactants can be equal or about equal to the stoichiometric amount for the formation of the desired beta-hydroxyalkyl carboxylate. For the preparation of the phthalic acid monoester, approximately 0.9 to 1.1 moles of alkylene oxide are taken per mole of acid. For the preparation of the bis-esters, a large excess of alkylene oxide is avoided, because this excess has no favorable effect on the yield of products, and therefore 1.8 to 2.5 are normally taken. or 3 moles of alkylene oxide per mole of phthalic acid.

   In the case of ethylene oxide and terephthalic acid, a narrower range is preferred, for example from about 2.0 to 2.2 or 2.5 moles of ethylene oxide per. mole of terephthalic acid.



   Rapid reactions are necessary for large-scale industrial execution. Condensation can be

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 carried out at a temperature ranging from about room temperature (25 C) to about 250 C, but generally being less than 200 C and normally 100 to 165 C, the precise temperature depending on the nature of the reagents present. At higher temperatures in the range 200 to 250 ° C, partial condensation of the bis (2-hydroxyalkyl) dicarboxylates initially formed can occur and results in the formation of low molecular weight polyesters which can be subjected to further polymerization into high molecular weight polyesters.

   For the preparation of bis (2-hydroxy ethyl) terephthalate, the working temperatures are preferably less than 200 ° C. and preferably about 100 to 165 ° C. The reaction can be carried out under atmospheric pressure.



  However, in the preferred embodiment of the invention, the reactions are carried out at elevated temperatures under pressures above that of the atmosphere, particularly when one or more of the reactants are gases, as in the case of ethylene oxide. When these elevated pressures are used, they may range from atmospheric pressure to 35.15 kg / cm2 or more, the pressure normally being 7.03 to 14.06 kg / cm2 at the gauge.



   It should be noted that time and temperature are interrelated variables and the time required for the reaction to be completed is very dependent on temperature. Generally, the reaction is essentially complete in about 3 minutes to 2 hours. At high temperatures of 200 to 250 C, times of 3 to 10 minutes may suffice.



   The process of the invention is carried out in the presence of a trivalent chromium catalyst. It is known that ethylene oxide can react with phthalic acid in the absence of a catalyst, but that the reaction is very slow and often does not reach its end. For the purposes of the invention, the concentration of carbon

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   The analyzer can vary over a wide range. This concentration generally ranges from about 0.01 to 5% by weight of the phthalic acid.

   The trivalent chromium salts useful as catalysts are chromium (III) octoate, chromium (III) acetate, chromium (III) benzoate, chromium (III) toluate, chromium (III) acetylacetonate, chromium (III) naphthenato, chromium (III) oleate, chromium (III) terephthalate, etc. The terephthalates can be added as is or formed in situ by adding the chromium (III) salt of a weak dibasic acid to the reaction mixture containing the terephthalic acid. Various inorganic compounds, such as chromium (III) oxide, copper chromite etc., are suitable.

   It has been found that hexavalent chromium compounds added to the reaction medium cause oxidation and are in turn reduced to chromotrivalent compounds and thus become effective as a catalyst.



   Other salts which can be used are trivalent chromium hexanoate, trivalent chromium pentanoate, trivalent chromium butyrate, trivalent chromium 2-ethylhexanoate, trivalent chromium decanoate, chromium oleate. trivalent, trivalent chromium 2-octenoate, trivalent chromium toluate, trivalent chromium cresylate, trivalent chromium benzoate, trivalent chromium alkylbenzpates, trivalent chromium alkoxybenzoates, trivalent chromium naphthenates, trivalent chromium alcoholates , mixed salts of trivalent chromium and chelates of trivalent chromium such as glycolates, acetylacetonates and versenates.

   Generally, but not necessarily, trivalent chromium catalysts have about 6 to 60 carbon atoms.



   According to the invention, it is also possible to use inorganic salts of chromium, such as chromic chloride, chromic fluoride and chromic hydroxide.

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   A specific embodiment of the invention is a process by which bis (2-hydroxyethyl) terephthalate can be isolated in good yields and acceptable purity for the preparation of high linear polyesters. molecular weight. More especially, the invention relates to various processes for isolating pure bis (2-hydroxyethyl) terephthalate with very low metal content and suitable for production on an industrial scale.



   In practice, the stoichiometric quantity of pressurized alkylene oxide, for example of ethylene oxide, is added to a suspension of the acid in a solvent containing the catalyst, for example to a suspension of terephthalic acid. than in toluene in the presence of chromium octoate, at the reaction temperature for the formation of the monomeric glycol terephthalate. A small excess of ethylene oxide, for example up to about 20% on a molar basis, can be added with advantage, but a substantial excess is also permissible.



  The solution is maintained at the reaction temperature of 100-200 C for about 3 minutes to 2 hours until the reaction is substantially complete, as indicated by the constancy of the pressure. The solvent is then removed, for example by distillation under reduced pressure, and the product is isolated in the form of a residue. Preferably, the solvent is removed at relatively low temperatures, for example below 100 ° C. and preferably below 80 ° C., so that the condensation of the monomeric glycol terephthalate into a low molecular weight polymer is avoided. The remaining ester can be purified by recrystallization from various solvents, such as water, methyl ethyl ketone, acetone etc.

   When water is the solvent for the recrystallization, the metallic impurities and in particular chromium, as well as the low molecular weight poly (ethylene terephthalate) from the residual bis-ester, are removed from the residue. substantially complete way. This eliminated

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 This allows a high purity product to be obtained for the subsequent polymerization. Since the monomer is intended for polymerization, it is not detrimental that it contains a small amount of the low molecular weight polyester resulting from the homopolymerization of hydroxyethyl terephthalate or from its reaction with. terephthalic acid.

   This phenomenon can take place during the reaction or during the removal of the solvent. Often an adsorbent such as activated carbon is used for the clarification of the above solutions.



   For carrying out the invention on a large scale, it is convenient to carry out the various operations by separate loads or continuously. For example, in a split batch process, the initial reaction can be carried out in a large autoclave, which is cooled after the reaction is complete and the operation subsequently being carried out in the usual batch fashion. Alternatively, the process can be carried out continuously by pumping the reactants, catalyst and solvent under suitable pressure through a heated tubular reactor or in a series of autoclaves arranged in stages and equipped with agitators. A variety of techniques allow a pure product to be obtained by a continuous process.

   When a substantially immiscible hydrocarbon or halohydrocarbon, for example toluene, xylene, chlorobenzene, ethylene chloride, hexane or octane, is selected as the solvent, the solvent can be removed by azeotropic distillation using water vapor when re-establishing atmospheric pressure. The residual aqueous solution can then be added with an adsorbent, such as charcoal, and this can then be removed by continuous filtration, centrifugation, decantation or other similar techniques, and then discarded.

   The clarified aqueous liquors can be evaporated under pressure.

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 Reauite and Continuously dried to give a pure product, or alternatively, after concentration in vacuo, they can be cooled for crystallization of bis (2-hydroxyethyl) terephthalate which is then continuously separated, dried. and conditioned. The residual liquors from this last operation are concentrated again under vacuum and recycled to the initial aqueous reaction mixture just before treatment with the adsorbent agent.



   Another method for continuous operation is to carry out the reaction in a hydrocarbon or halohydrocarbon as a solvent. However, before re-establishment of atmospheric pressure, the reaction mixture should pass through a cooling zone. After re-establishing atmospheric pressure, the hot reaction mixture can be diluted with solvents, such as acetone or methyl ethyl ketone, in a ratio ensuring complete miscibility.



   The solution is then added with an adsorbent, which can be removed by continuous filtration, decantation or centrifugation.



   The clarified liquors can then be freed of acetone or methyl ethyl ketone, after which the residual liquors can be cooled for the isolation of bis (2-hydroxyethyl) terephthalate crystals. These crystals can then be separated continuously. , for example by centrifugation or filtration, then dried. Hydrocarbon. or the remaining halohydrocarbon is returned to a continuous recovery column and recycled to the initial reaction.



   Yet another technique for carrying out the continuous process would be to conduct the reaction of ethylene oxide with terephthalic acid and the chromium salt catalyst in a miscible solvent such as methyl isobutyl ketone. The hot reaction mixture, after some cooling and reestablishment of atmospheric pressure, is then removed.

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 continuously removed from the solids, after which the methyl isobutyl ketone is completely removed by means of water vapor.



  The recovered methylisobutyl ketone is then recycled after drying to the initial reaction. The aqueous solution remaining after the entrainment by the steam is added to an adsorbent, for example charcoal, then clarified continuously, the adsorbent then being discarded. The clarified aqueous liquors are then evaporated in vacuo and dried continuously to give a pure product, or the concentrated liquors are cooled for crystallization of the product which is then collected and dried. The mother liquors are concentrated again and recycled to adsorption and clarification. A variant of the process consists in extracting the clarified methyl isobutyl ketone from the reaction mixture with a counterflow of hot water.

   The resulting spent methyl isobutyl ketone is then dried and freed from water, then recycled to the inlet reactor. The aqueous extracts are meanwhile concentrated in vacuo and brought to the clarification stage above for the addition of the adsorbent, the subsequent operations being the same as above.



   Generally, when an inert liquid solvent is not used, the phthalic acid and the chromium catalyst are combined, then the slurry is pumped into a heated reaction zone and ethylene oxide is therein. introduced in streams in the same or opposite directions. After an appropriate reaction time which depends on the catalyst concentration and the reaction temperature (normally 25 to 250 ° C), the reaction mixture is withdrawn. At this time, various treatment routes are possible.

   One of the variants consists in cooling a part of the reaction mixture corresponding to the amount of acid added to a temperature below about 130 ° C., but above the melting point.

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 from the reaction medium (usually about 100 to 110 ° C.) and to separate the residual catalyst and any unchanged phthalic acid, which are recycled on admission to uvoc most of the molten reaction mixture. Alternatively, a fraction of the reaction mixture corresponding to the amount of phthalic acid added is dissolved in water and the insoluble catalyst, together with the unchanged acid, is separated, dried and recycled to the point of admission with most of the reaction mixture has melted.



  In the first case, the fraction of the clarified mixture is dissolved in water and is then in the same state as in the second case mentioned above.



   In either case, the aqueous ester solution is then cooled for crystallization.



  The crystals are separated and purified in the usual manner with additional fresh water. Preferably, all subsequent operations use the filtrates from the previous purifications flowing countercurrently to the reaction product, so that the crude product is always dissolved in a saturated solution from the previous purification. Thus, a stream of fresh water is always available for the final purification, while a stream of waste water is taken during the initial recrystallization. Depending on the reaction temperature and the nature of the catalyst, it is sometimes necessary to use an adsorbent or a deionization agent, such as charcoal, alumina, silica gel, a cation exchange resin, etc. , for the first stage of recrystallization.

   However, the use of adsorbents or deionizing agents is not absolutely necessary for the preparation with a good yield of a substantially pure ester.



   The details given above simply illustrate a few of the many possible continuous embodiments of the process of the invention. The invention is dayantage

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 illustrated without being limited by the following examples: EXAMPLE 1 -
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 t) 1'Ó0nr: 1 tion du tth'phtalato 'do bic (2-hydl'oxx4th: llçl A. By means of a conventional laboratory apparatus under the pressure
 EMI16.2
 atmospheric pressure,
The apparatus used for this test is a three-necked round-bottom flask with a capacity of 1 liter fitted with a stirrer, a thermometer and a reflux condenser. Methyl isobutyl ketone (300 ml: and terephthalic acid (41.5 g, 0.25 mol) is introduced into the clean flask.

   To this suspension, ethylene oxide (24.2 g, 0.55 mol, i.e. a molar excess of 10%) is added directly containing chromium octoate in sufficient quantity (0.415 g) to represent 1 % by weight of acid. With stirring, the temperature is raised and maintained between 40 and 50 C. From time to time, to qualitatively assess the progress of the reaction, samples are taken which are subjected to infrared analysis to observe the disappearance. of the absorption band of the carbonyl radical of the acid (1700 to 1710 cm-1).

   After 8 hours, the reaction suspension is filtered while hot and the solid is washed twice with acetone. The solid is dried, then weighed (24.48g), after which it is established that it is formed of unchanged terephthalic acid by examining its infrared spectrum (ab-
 EMI16.3
 sorption at 1700 m-1 (C = 0 and its melting point (300 300 C.) With stirring, the filtrate (400 ml) is added to a mixture of hexanes (1200 ml) to precipitate the terephthalic ester.
 EMI16.4
 We re-mix by fj * ltrqtjon lp precipitated solid which is dried and weighed (25.8 g, 0.102 mol) and which is established by means of the infrared spectrum (3500 cm-1 (011, melting point and elemental analysis, that it is formed by terephthalate
 EMI16.5
 of b.s (2-hydroxyethylj.

   Under these conditions, the conversion of the acid is 41% and the recovery in isolated product is 99%.



   In a similar test carried out under the same conditions,

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 but in ethylene dichloride instead of methyl isobutyl ketone as the solvent, the acid conversion is 17.35% and the ester yield is 98%.



  B. Using a 1 liter autoclave
For this test, the reactor is a stainless steel autoclave with a capacity of 1 liter fitted with a magnetic stirrer and the usual accessories.



   Methyl isobutyl ketone (500 ml) containing chromium loctoate in sufficient quantity (0.415 g) is introduced into the clean reactor to represent 1% of the weight of terephthalic acid which is taken in an amount of 41.5 g, 0, 25 mole. The autoclave is closed, then ethylene oxide (24.2 g, 0.55 mol, or a molar excess of 10%) is admitted from a bottle. The air-powered magnetic stirrer is then operated. The temperature is allowed to rise until the pressure is 2.11 kg / cm2 on the manometer.

   When the temperature is reached, the pressure drops in 2 hours and 15 minutes to 0.88 kg / cm2 on a manometer (probably the partial pressure of methyl isobutyl ketone at 90 ° C.). The entire system is cooled to 50 ° C., then the pressure is released and the contents of the apparatus are introduced into a glass container. The reaction mixture is filtered and the filtrate (600 ml) is divided into three equal fractions, each of 200 ml. To fraction A, a mixture of hexanes (600 ml) is added to precipitate the terephthalic ester. The product is filtered, then washed with hexane, dried and weighed (21.0 g, 0.0826 mole).



  To fraction B is added 3 g of activated carbon at 40-50 C, the mixture is stirred for 30 minutes, then filtered and cooled to room temperature, after which the product is precipitated by adding the mixture. hexanes to the solution. The solid is filtered, dried and weighed (21.2 g, 0.0833 mol).



  The C fraction is cooled to 5-10 C and collected by filtration.

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 tion the precipitated solid which is dried and weighed (13.9 g,
0.055 mole). Under these working conditions (90 C / 2.11 kg / cm2 at a manometer), the conversion of terephthalic acid is quantitative and the ester is isolated with a yield of 99.5% (fraction
A), 100% '(fraction B), 66% (fraction C).



    .EXAMPLE 2 -
Preparation of various terephthalates
1,2-epoxybutane and epoxyoxyhexane, respectively, in the absence of solvent, are reacted with terephthalic acid by adding a small amount of chromium octoate in a glass apparatus operating at atmospheric pressure. After 4 hours at a temperature of 60 to 65 C, the esters are isolated. Bis (2-hydroxybutyl) terephthalate melts at about 104-106 C. Bis (2-hydroxycyclohexyl) terephthalate melts at about 124-130 C.



    EXAMPLE 3 - Solvent test in a 1 liter autoclave
The low boiling point (10 ° C) of ethylene oxide limits the reaction temperature which can be reached in the presence of a solvent, except when working under pressure.



  The first series was carried out in an autoclave using industrial grade terephthalic acid in the presence of a solvent. The results are shown in Table I below. for all tests; the molar ratio is 1 mole of terephthalic acid per 2.2 moles of ethylene oxide. and the amount of chromium octoate is 1% (based on the weight of the acid). The column entitled pressure indicates the evolution of the pressure during the reaction. The conversion is the percentage of tereph talic acid converted to other products and the yield is the percentage of product isolated on the basis of the acid converted.

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  @
 EMI19.1
 IQ
 EMI19.2
 
<tb> Cogitions <SEP> of <SEP> reaction
<tb> Pressure
<tb>
 
 EMI19.3
 Solvent ', * oc - I ± dcn-. 2 aa ri [no, a% -tre Time in hours Conversion Yield None 160-165 9.49-7.94 - 4.00 10.0 d Acetone 160-165 14.06-5.27 1.75 96, 75 87.2 2-Butanone 75 0-1.83-1.27 3.75 49.5 87.1a Ethyl isobutyl ketone 90 0-2.11-0.88 2.25 "100.0 66.0
 EMI19.4
 
<tb> 100.0a
<tb> 100.0
<tb> Dioxane <SEP> 160-165 <SEP> 1.50 <SEP> 100.0 <SEP> d
<tb>
 
 EMI19.5
 Ethylene glycol z 160-165 1.50 0.0 -
 EMI19.6
 
<tb> Water <SEP> 160-165 <SEP> 1.50 <SEP> 3.0 <SEP> Ethanol <SEP> 160-165 <SEP> l, 50 <SEP> 83.7 <SEP> d
<tb>
 
 EMI19.7
 1.io.nochlorobenzene 160-165 1.50 98.3 d
 EMI19.8
 
<tb> Toluene <SEP> 160-165 <SEP> 1, <SEP> 50 <SEP> 100.0 <SEP> d
<tb> Toluene / acetone <SEP> 160-165 <SEP> 1.25 <SEP> 85.0 <SEP> d
<tb> Xylene <SEP> 160-165 <SEP> 1.50 <SEP> 100,

  0 <SEP> d
<tb>
 
 EMI19.9
 1,2-dj, ctii.oioôNià = ie 160-165 1.76-5.2 -:?, 61 2.0 99.2 80.0 ara Weight ratio trep acid: ltaJ.i <1Ue: solvent of 1 : 5. a Aliquot (in 1.?lume) c :: ddltionn8c of a z:. ': l <:. nse of hexanes for the precipitation of the product (a part of Cé'tJnîrjUf 1> OUt 3 Prr4q- "solution, -rj- ,, dhexar-es). b Aliquot of ketone solution cooled to 5-10 C, then filtered and dried. c aliquot with the addition of activated carbon at 40-50 C stirred for 33 minutes, filtered and cooled with
 EMI19.10
 
<tb> ambient <SEP> temperature <SEP> before <SEP> the <SEP> precipitation <SEP> of <SEP> produced <SEP> by <SEP> addition <SEP> of a <SEP> mixture <SEP> d 'hexanes.
<tb> d <SEP> Efficiency <SEP> not <SEP> determined.
<tb>
 

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  EXAMPLE 4 - Variation of the solvent: acid ratio
A series of preparations of the ester are carried out in the autoswitch by varying the solvent: acid ratio to assess the effect of this ratio, the solvent being methyl isobutyl ketone. The results are given in Table II. 1 mole of terephthalic neide is taken for 2.2 moles of ethylene oxido.



  The reaction is carried out at 160-165 C for 30 minutes, then on. filter the mixture and pour it into n-hexane to precipitate the product. The product is collected and dried. The melting points and the saponification indices of the esterdiols are measured and the values are corrected for the acidity (theoretical saponification index of 440.5). The conversion of the acids is more than 98% and the yield of isolated product is more than 95%.



     TABLE II
 EMI20.1
 
<tb>
<tb> <SEP> weight ratio <SEP> <SEP> index of <SEP> saponification
<tb> acid / solv <SEP> ant <SEP>
<tb> 1 <SEP> / <SEP> 6 <SEP> 452
<tb> 1 <SEP> / <SEP> 9 <SEP> 428
<tb> @ <SEP> 1 <SEP> / <SEP> 12 <SEP> / <SEP> 12 <SEP> 429
<tb>
 EXAMPLE 5 Method of Addition of Ethylene Oxide
By carrying out the reaction in the autoclave, the effect of the mode of addition of ethylene oxide on the reaction time among others is studied. The reactions are carried out at 160-165 ° C. taking 1 mole of terephthalic acid per 2.2 moles of ethylene oxide and 1% of chromo octoate (based on the weight of the acid).



  The product is isolated as in Example 4. The conversion of the acid is quantitative and the yield of product is more than 95%. The results are given in Table III.

 <Desc / Clms Page number 21>

 
TABLE III
 EMI21.1
 
<tb>
<tb> Mode <SEP> of addition <SEP> of <SEP> the oxide <SEP> Duration <SEP> of <SEP> Index <SEP> of <SEP> sapo-
<tb>
 
 EMI21.2
 d> ethylene reactlon, hours nification8
 EMI21.3
 
<tb>
<tb> Addition <SEP> of the <SEP> catalyst <SEP> to the
<tb> chrome <SEP> in <SEP> ethylene oxide <SEP> <SEP> at <SEP> <SEP> temperature <SEP> of
<tb> reaction <SEP> 2.00 <SEP> 428
<tb> Addition <SEP> of <SEP> ethylene oxide <SEP> <SEP> directly <SEP> to the <SEP> mixture
<tb> of <SEP> reaction <SEP> containing <SEP> the
<tb> catalyst <SEP> at <SEP> the <SEP> temperature
<tb> of <SEP> reaction <SEP> 0,

  50 <SEP> 429
<tb> Addition <SEP> of <SEP> ethylene oxide <SEP> <SEP> to the <SEP> mixture <SEP> of <SEP> reaction
<tb> containing <SEP> the <SEP> catalyst, but
<tb> before <SEP> the <SEP> heating <SEP> 2.25 <SEP> 432
<tb>
 a The saponification index is theoretically 440.5.



  EXAMPLE 6 -
 EMI21.4
 Variation in the ratio of acid-terenhtaliou: ethylene orde
Various tests were carried out to assess the effect of the terephthalic acid: ethylene oxide molar ratio on the conversion. The reaction conditions and the mode of isolation of the product are the same as in Example 4. The results are given in Table IV.



   TABLE IV
 EMI21.5
 
<tb>
<tb> Molar <SEP> ratio
<tb> <SEP> terephthalic acid / <SEP> Conversion, <SEP>% <SEP> Yield, <SEP>% <SEP>
<tb> ethylene <SEP> oxide
<tb> 1 <SEP> / <SEP> 1.6 <SEP> 78.5 <SEP> 98
<tb> 1 <SEP> / <SEP> 2.2 <SEP> ¯ <SEP> 98.0 <SEP> 98
<tb> 1 <SEP> / <SEP> 2.4 <SEP> 100.0 <SEP> 99
<tb>
 EXAMPLE 7 -
 EMI21.6
 Kinetic studies A.

   At various temperatures
A kinetic study is carried out to establish the most favorable reaction temperature for the synthesis of bis (2-hydroxyethyl) terephthalate from terephthalic acid (1.0 mol) and ethylene oxide, (2.2 moles), in the presence of 1% chromium octoate (based on the weight of the acid) as a catalyst, and

 <Desc / Clms Page number 22>

 , methyliobutyl ketone (800 g) as solvent, in an autoclave,
All components except ethylene oxide are introduced into the autoclave which is heated with stirring.

   In all cases, ethylene oxide is introduced when the required temperature. is achieved by exerting pressure with nitrogen (17.56 kg / cm2 on a manometer), which causes an exothermic reaction (heating from 10 to 20 C) with a rise in pressure.



     After the exothermic reaction, the pressure and temperature of the system begin to decrease. When the pressure stops decreasing, at about the required reaction temperature, the reaction is considered to be complete. The mixture is cooled. reaction at 80 C, then filtered and poured into n-hexane to precipitate the esterdiol. After filtration, the crude product is dried to determine the yield. The conversion of the acid is quantitative and the yield of isolated product varies with the reaction temperature. The results are given in Table V.



   TABLE V
Reaction conditions
 EMI22.1
 
<tb>
<tb> Tempera- <SEP> Duration <SEP> for <SEP> Couver- <SEP> Rende- <SEP> Index
<tb> ture, <SEP> C <SEP> Pressure <SEP> completion <SEP> sion, <SEP> ment, <SEP>% <SEP> from <SEP> sapokg / cm2 <SEP> to <SEP> from <SEP> the <SEP> con <SEP> b <SEP> c <SEP> nification
<tb> manoeter a <SEP> version <SEP> in <SEP> d
<tb> ¯¯¯¯¯ <SEP> ¯¯¯¯¯¯¯ <SEP> minutes <SEP> ¯¯¯¯. <SEP> ¯¯¯¯¯ <SEP> ¯¯¯¯¯¯¯
<tb> 121-130 <SEP> 7.38-3.09 <SEP> 86.0 <SEP> 100 <SEP> 95.6 <SEP> 424
<tb> 141-146 <SEP> 9.14-2.88 <SEP> 56.0 <SEP> 100 <SEP> 94.2 <SEP> 421
<tb> 160-162 <SEP> 7.38-2.04 <SEP> 33.0 <SEP> 100 <SEP>. <SEP> 98.0 <SEP> 424.
<tb>



  174-176 <SEP> '<SEP> 11.18-3.59 <SEP> 21.0 <SEP> 100 <SEP> 92.0 <SEP> 423
<tb> 192-195 <SEP> 12.65-6.05 <SEP> 11.0 <SEP> 100 <SEP> 92.5 <SEP> 426
<tb> 205-216 <SEP> 14.69-9.07 <SEP> 8.0 <SEP> 100 <SEP> 96.0 <SEP> 431
<tb> 218-225 <SEP> 14.62-8.37 <SEP> 4.5 <SEP> 100 <SEP> 88.7 <SEP> 434
<tb> 238-240 <SEP> 17.58-10.69 <SEP> ¯ <SEP> 3.5 <SEP> 98 <SEP> 87.3 <SEP> 438
<tb>
 aThe pressure column indicates the evolution of the pressure from the moment of the addition of ethylene oxide until the

 <Desc / Clms Page number 23>

 pressure becomes constant again. bConv ersion of terephthalic acid into other compounds. c Yield of isolated product on the basis of converted acid. dTheoretical value of the saponification index: 440.5.



   B. At various catalyst concentrations
Trivalent chromium octoate is used in various amounts (0.4 to 1.0% by weight of the acid) to establish the most favorable concentration of catalyst for the synthesis of bis-2 (hydroxyethyl terephthalate). ) from purified terephthalic acid (0.25 mole) and ethylene oxide (0.55 mole). The operations are carried out in an autoclave at 160-165 C in methyl isobutylketon (200 g) as a solvent. The product is isolated as in Example 7A. The conversion of the acid is practically quantitative. The results of Example 7B are given in Table VI.



   TABLE VI
Reaction conditions
 EMI23.1
 
<tb>
<tb>% <SEP> of octoate <SEP> Duration <SEP> required <SEP> kg / cm2 <SEP> at <SEP> ma- <SEP> Rende- <SEP> Index <SEP> of
<tb> of <SEP> chromea <SEP> for <SEP> a <SEP> conver- <SEP> nometer <SEP> ment,% <SEP> saponifica
<tb> sion <SEP> plot, <SEP> tione
<tb> ¯¯¯¯¯¯¯ <SEP> in <SEP> minutesb
<tb> l, 00 <SEP> 33 <SEP> 7,38-2,11 <SEP> 98,0 <SEP> 423
<tb> 0.50 <SEP> 43 <SEP> 8.08-4.36 <SEP> 96.0 <SEP> 423
<tb> 0.40 <SEP> 67 <SEP> 9.84-4.07 <SEP> 97.5 <SEP> 423
<tb> 0.25 <SEP> 88 <SEP> 9.14-4.34 <SEP> 98.0 <SEP> 424
<tb>
 The percentage of trivalent chromium oetoate is given on the basis of the weight of the acid. bConversion of terephthalic acid into other products eTheoretical saponification index is 440.5.



   EXAMPLE 8 E @ sai of catalysts
We're running a series. were using various cata-

 <Desc / Clms Page number 24>

 Chromium lyscurs in a concentration of 1% by weight in a stainless steel autoclave fitted with a magnetic stirrer. All reactions were carried out at 105-1100C in methyl isobutyl ketone (800 g), the conduct of the reaction and the isolation of the product being the same as in Example 7A. The results of Example 8 are shown in Table VII.



   TABLE VII
 EMI24.1
 
<tb>
<tb> Catalyst <SEP> Quantity <SEP> of <SEP> cataly- <SEP> Conditions <SEP> of
<tb>
 
 EMI24.2
 shur o3.ds,. # ¯¯.action.¯ tr: '.' nn. & <? j1.Pr.- --pjnc.tj¯Qn - ln7 and-t rfà eî- in dec kg / cn2 at Duration , Conversi ¯¯¯¯¯¯¯ le selb ¯¯¯¯¯¯¯ manometer (d) hours%
 EMI24.3
 
<tb>
<tb> None <SEP> 4.92-2.25 <SEP> 4.00 <SEP> 1.5
<tb> Octoate <SEP> from
<tb> chrome <SEP> (III) <SEP> 10.5 <SEP> 0.105 <SEP> 2.11-0.91 <SEP> 2.25 <SEP> 100.0
<tb> Chromium <SEP> acetylacetonate <SEP>
<tb> (III) <SEP> 15.0 <SEP> 0.150 <SEP> 6.12-1.69 <SEP> 2.75 <SEP> 99.7
<tb> Acetate <SEP> of
<tb> chrome <SEP> (III) <SEP> 23.0 <SEP> 0.230 <SEP> 5.76-1.97 <SEP> 3.75 <SEP> '<SEP> 90.2
<tb> Naphthenate
<tb> from <SEP> chrome
<tb> (III) <SEP> 5.8 <SEP> 0.058 <SEP> 5.20-1.05 <SEP> 4.01 <SEP> 100.0
<tb> Oleate <SEP> do
<tb> chrome <SEP> (III) <SEP> 5.0 <SEP> 0.050 <SEP> 5,

  98-1.48 <SEP> 3.50 <SEP> 100.0
<tb> Oxide <SEP> of
<tb> chrome <SEP> (III) <SEP> 68.4 <SEP> 0.684 <SEP> 8.01-3.66 <SEP> 4.00 <SEP> 93, <SEP> 0 <SEP>
<tb> Chromite <SEP> from
<tb> copper <SEP> 33.4 <SEP> 0.334 <SEP> 7.59-3.44 <SEP> 4.00 <SEP> 85.5
<tb> Dichromate
<tb> '<SEP> of <SEP> potassium <SEP> 35.4 <SEP> 0.354 <SEP> 6.47-0.84 <SEP> 4.23 <SEP> 81.6
<tb> Octoate <SEP> from
<tb> chrome <SEP> (III) /
<tb> N, <SEP> N-dimethylbenzylaminea <SEP> 6.6 <SEP> 0.066 <SEP> 4.92-2.04 <SEP> 2.36 <SEP> 100.0
<tb>
 2: 1 weight ratio.



  Percentage of chromium in the catalyst. ePercentage of chromium based on the weight of the acid.



  Evolution of the pressure during the reaction.

 <Desc / Clms Page number 25>

 



    EXAMPLE 9 - Effects of Solubility '' II
The solubility of bis (2-hydroxyethyl) terephthalate is determined at various temperatures for purification.



  Various solvents were tested for the various temperatures, giving the results shown in Table VIII.



   TABLE VIII
 EMI25.1
 
<tb>
<tb> Solubility <SEP> * <SEP> of <SEP> terephthalate <SEP> of <SEP> bis (2-hydroxyethyl) <SEP> in <SEP> various
<tb> ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯solvents¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
<tb> Temp. <SEP> C <SEP> Methyliso- <SEP> Water <SEP> Toluene <SEP> Methylethyl- <SEP> Acetone
<tb> butylce- <SEP> ketone
<tb> tone <SEP> ¯¯¯¯¯ <SEP> ¯¯¯¯¯¯¯¯¯¯ <SEP> ¯¯¯¯¯¯
<tb> 0 <SEP> 1.15 <SEP> 0.26 <SEP> - <SEP> 5.5 <SEP> 0.69 <SEP> '<SEP>
<tb> 25 <SEP> 2.01 <SEP> 0.92 <SEP> 0.11 <SEP> 6.6 <SEP> 12.0
<tb> 60 <SEP> 8.83 <SEP> 60.5- <SEP> 33.0 <SEP> 62.0
<tb> 70- <SEP> - <SEP> 0.89 <SEP> 55.5 <SEP> -
<tb> 80 <SEP> 34.3 <SEP> 79.4 <SEP> - <SEP> - <SEP> -
<tb> 100 <SEP> 97,0- <SEP> 4,

  98 <SEP> - <SEP> -
<tb>
 * Percentage by weight EXAMPLE 10 - Isolation and purification of the product
This example makes it possible to appreciate the various techniques for isolating and purifying bis (2-hydroxyethyl) terephthalate for the economical application of the process. For poly (ethylene terephthalate) polymerization, bis (2-hyaroxyethyl) terephthalate monomer should have a melting point falling within a narrow range, good coloring (white), low heavy metal content (< 3 ppm) and good purity determined by the saponification number (theoretical value 440.5).



  In this series of tests, terephthalic acid (1.0 mol) is reacted with ethylene oxide (2.2 mol) in the presence of 1% chromium octoate, based on weight of the acid, at 160-165 C in a 1 liter autoclave in the presence of various. 501-

 <Desc / Clms Page number 26>

 vants (800 g). Various techniques for the isolation and purification of the product are examined (Sections A, B, C and D below) and the metal contents of these products are determined by emission spectroscopy, as well as the terephthalate contents. of hydroxyethyl via the saponification number (the theoretical value of which is 440.5). The results below show the differences in technique and product quality.



   For the convenience of comparison, analogous isolation and purification procedures are contemplated for the different solvents and the products are compared.



   A. Purification of Crude Hydroxyethyl Terephthalate Using Water
In the first series of tests, the reaction is carried out as described above in methyl isobutyl ketone, toluene or xylene, then the solvent is removed completely in vacuo, the crude product is dissolved in hot water. (50 to 60 ° C.), it is sometimes decolorized with charcoal, filtered, the filtrate is cooled to room temperature to precipitate the product and the latter is isolated by filtration. The product is dried and its purity is determined, as is its metal content. The results are shown in Table IX.



   TABLE IX
Purification of Crude Hydroxyethyl Terephthalate Using ¯¯¯¯¯ Water Product
 EMI26.1
 
<tb>
<tb> Solvent <SEP> Yield,% <SEP> PF, C <SEP> Colora- <SEP> Index <SEP> Content <SEP> in <SEP> metion <SEP> .of <SEP> sapo- <SEP> heavy <SEP> rates,
<tb> nifica- <SEP> ppm
<tb> ¯¯¯¯¯¯ <SEP> ¯¯¯¯¯ <SEP> tionb
<tb> Methylisobu- <SEP> not <SEP> of <SEP> Cr;
<tb> tylc6tone <SEP> 84 <SEP> 108-109 <SEP> white <SEP> 443.0 <SEP> others <SEP> <<SEP> 1
<tb> Methylisobu- <SEP> not <SEP> of <SEP> Cr;
<tb> tylketonea <SEP> 86 <SEP> 108.5-109 <SEP> "<SEP> 440.5 <SEP> others <SEP> <<SEP> 1
<tb> Xylene <SEP> 89 <SEP> 108.5-109 <SEP> "<SEP> 440.0 <SEP> not <SEP> of <SEP> Cr;
<tb> others <SEP> <<SEP> 1 <SEP>
<tb> Toluènea <SEP> 92 <SEP> 109-109, <SEP> "<SEP> 440.2 <SEP> Cr-3;

  
<tb> others <SEP> <<SEP> 1
<tb> Toluene <SEP> 92 <SEP> 108.5-109.5 "<SEP> 439.0 <SEP> Cr-3;
<tb> others <SEP> <<SEP> 1
<tb>
 

 <Desc / Clms Page number 27>

 with an addition of 5% activated carbon based on the weight of the crude solid. bTheoretical value of the saponification number is 440.5.



  B. Purification of crude hydroxyethyl terephthalate by filtering methyl isobutyl ketone solution in n-hexane
The products obtained in a series of tests are compared in which the solution of the crude product in methyl isobutyl ketone is treated with activated carbon and introduced by filtration (so as to retain the terephthalic acid unchanged and insoluble chromium compounds) in n-hexane, resulting in precipitation of the product which is then collected, dried and analyzed. The results are shown in Table X.



   TABLE X Purification of hydroxyethyl terephthalate by filtration of its ¯¯¯¯¯¯¯ methyl isobutyl ketone solution in n-hexane
Product
 EMI27.1
 
<tb>
<tb> Solvent <SEP> Rende- <SEP> P.F., C <SEP> Colora- <SEP> Index <SEP> Metals <SEP> content <SEP>
<tb> of <SEP> ment,% <SEP> tion <SEP> of <SEP> snpo- <SEP> heavy, ppm
<tb> reaction <SEP> nification
<tb> Methylisobutylce- <SEP> white
<tb> tone <SEP> 98.0 <SEP> 103-109 <SEP> broken <SEP> 425.0 <SEP> Cr-2 <SEP>; <SEP> others <SEP> <<SEP> 1
<tb> Toluene <SEP> 96.0 <SEP> 108.5-109 <SEP> white <SEP> 433.0 <SEP> not <SEP> of <SEP> Cr; <SEP> others <SEP> <1
<tb> Xylene <SEP> 92.0 <SEP> 108-109 <SEP> white <SEP> 440.2 <SEP> Cr-3; <SEP> others <SEP> <1
<tb>
 vs.

   Isolation and purification of hydroxyethyl terephthalate by extraction with water
Multiple water extractions from the reaction product mixture (the solvent being methyl isobutyl ketone or toluene) are carried out at various temperatures at various temperatures, after which the mixture is filtered and cooled to precipitate the product which is isolated by filtration, which is dried and analyzed.



  The results are given in Table XI.

 <Desc / Clms Page number 28>

 



   ---- TABLRAU XI
 EMI28.1
 Isolation and purification of dl.hydroxyethyl terephthalate by extraction with 1.1 water. -
Product
 EMI28.2
 
<tb>
<tb> Solvent <SEP> Temp. for <SEP> Rende- <SEP> P.F., C <SEP> Colo- <SEP> Index <SEP> Content <SEP> in
<tb> from <SEP> extraction <SEP>,% <SEP> ra- <SEP> from <SEP> sa- <SEP> Metals <SEP> heavy <SEP>
<tb> reaction <SEP> tion, C <SEP> e <SEP>? o <SEP> tion <SEP>. <SEP> ponifi- <SEP> ppm
<tb>
 
 EMI28.3
 ¯ ¯ ¯ ¯ cation ¯¯¯¯¯¯¯¯
 EMI28.4
 
<tb>
<tb> Methylisobutyl- <SEP> Cr-5;
<tb> ketone <SEP> 40-50 <SEP> 18.0 <SEP> 104-106 <SEP> white <SEP> 432.0 <SEP> 'others <SEP> <1
<tb> Toluene <SEP> 40-50 <SEP> 56.0 <SEP> 108-110 <SEP> white <SEP> 438.0 <SEP> Cr-20;
<tb> others <SEP> <<SEP> 1
<tb> Toluene <SEP> 40-50 <SEP> 56.5 <SEP> 109-110 <SEP> white <SEP> 440.8. <SEP> Or-30;

  
<tb> others <SEP> <<SEP> 1
<tb> Toluene <SEP> 70-80 <SEP> 79.0 <SEP> 108.5- <SEP> white <SEP> 439.0 <SEP>. not <SEP> of <SEP> Cr;
<tb> 109.5 <SEP> others <SEP> <<SEP> 1
<tb>
 We do not try to achieve the optimum result with regard to the most efficient temperature and the number of extractions: the most useful; the treatment with an adsorbing agent decreases the heavy metal content as in the other cases.



  D. Isolation and purification of hydroxyethyl terephthalate '(from a solution in toluene and a ketone by filtration and distillation) ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
For the tests of this series, which relates to Table XII, the reaction of terephthalic acid on the oxide is carried out.
 EMI28.5
 ethylene in toluene at 160-lb5 C in the presence of 1% cobalt terephthalate (based on the weight of the acid). Since hydroxyethyl terephthalate has a very limited solubility in toluene, a suitable mode of isolation of this compound is to add a ketone, which solubilizes the hydroxyethyl terephthalate undissolved in toluene at any temperature. .



  The solution is then filtered (to separate the optional unchanged terephthalic acid and insoluble chromium compounds), then the ketone is removed by distillation, the resulting solution is cooled and filtered. The resulting product is dried and

 <Desc / Clms Page number 29>

 The various variations of this procedure give the results shown in the table. Ketones are chosen because of their ability to dissolve a large amount of hydroxyethyl terephthalate at a reasonable temperature (50-70 C) and because of their inability to form an azeotrope with toluene.



   TABLE XII
 EMI29.1
 Isolation of hydroxvethyl tereohthalate from solutions in toluene and a ketone by filtration and distillation)
Product
 EMI29.2
 
<tb>
<tb> Solvent <SEP> 'Ketone <SEP> Rende- <SEP> PF, C <SEP> Colo- <SEP> Index <SEP> Content <SEP> in <SEP> mede <SEP> elimination <SEP> <SEP> <SEP> ration of <SEP> its- <SEP> heavy <SEP> rate ,,
<tb> reaction <SEP> nee <SEP> ponifi- <SEP> p <SEP> p <SEP> m
<tb>
 
 EMI29.3
 '¯¯¯¯, ¯, ¯¯¯¯¯ cation, -
 EMI29.4
 
<tb>
<tb> Toluene <SEP> Acetone <SEP> 94.2 <SEP> 108.5- <SEP> white <SEP> 439.2 <SEP> not <SEP> of <SEP> Cr;
<tb> 109.5 <SEP> others <SEP> <1
<tb> Toluene <SEP> 2-buta- <SEP> 95.5 <SEP> "108.5- <SEP> white <SEP> 439.7 <SEP> not <SEP> of <SEP> Cr;

  
<tb> none <SEP> 109 <SEP> others <SEP> <<SEP> 1
<tb> Toluene / <SEP> Acetone <SEP> 93.0 <SEP> 109.5- <SEP> white <SEP> 438.3 <SEP> not <SEP> ae <SEP> Cr:
<tb> acetone <SEP> 110 <SEP> others <SEP> <<SEP> 1
<tb> Methyliso- <SEP> Acetone <SEP> 96.0 <SEP> 108.5- '<SEP> white <SEP> 438.0 <SEP> not <SEP> of <SEP> Cr;
<tb> butylc- <SEP> 109 <SEP> others <SEP> 41, <SEP>
<tb> tone
<tb>
 aMethyl isobutyl ketone is completely evaporated from the crude product and the latter is dissolved in a mixture of toluene and acetone. bThe various ketones are removed by vacuum distillation.



    EXAMPLE'11 -
83 g (0.5 mol) of industrial grade terephthalic acid and 500 ml of toluene are introduced into a 1 liter autoclave containing 0.83 g (1% by weight of the acid) of chromium octoate as a dispersion. . The system is heated by agitation and, after reaching a temperature of 130 ° C., an internal pressure of 0.70 kg / cm 2 is reached at the gauge. At this time, 53 g (1.2 mole) of ethylene oxide are injected by means of pressurized nitrogen. The temperature quickly reached 139 C and the -pressure 5.27 kg / cm2 on the manometer.

   After 90 minutes, the temperature
 EMI29.5
 rature falls back to 130 C and.JA .. pressure reaches a constant value- ".J - w:; ro ..- ....:. ':" ""' n "" '' '' .'- < 1¯ - l> -----.- ,, -. = 9:> '- "' r '"' ". ':"' '' * "" '\.' J: '- ::. '', -.......-...

 <Desc / Clms Page number 30>

 te of 2.53 kg / cm2 on a pressure gauge. The autoclave and its contents are cooled to 105 ° C., then the reaction mixture is withdrawn therefrom. The toluene is removed by azeotropic distillation with 500 ml of water, then 12.7 g of charcoal (10% of the theoretical weight of the product) are added to the aqueous dispersion of the crude ester which remains. what we filter the mixture hot. On cooling, the mixture deposits white crystals.

   The solids are collected by filtration, then washed twice with cold water and dried to obtain 115 g (90.5% yield) of pure ester melting at 108.5 at 1090C and having an index of saponification of 440.2 (theoretical value 440.5). Analysis indicates that the chromium content is zero and the iron content is only 1 ppm.



   EXAMPLE 12 -
The process of Example 11 is repeated, but on leaving the autoclave, the reaction mixture is cooled to 560C and 250 ml of acetone are added thereto. Charcoal is added to the resulting solution and filtered. After removing the acetone by evaporation of the clarified solution, the product is crystallized from the remaining toluene. We cool the m-. mix and filter it. The collected crystals were washed twice with fresh toluene, then dried to obtain
119.5 g (94.2% yield) of pure bis (2-hydroxyethyl) terephthalate, melting at 108.5 to 109 C. The saponification index of the product is 439.2 (theoretical value 440, 5) and its heavy metal content is zero.



    EXAMPLE 13 -
The process of Example 12 is repeated, but taking
250 ml of methyl ethyl ketone instead of acetone. In this case, 121 g '(95.5% yield)' of pure product melting at 108.5 - 109.0 C. are isolated. The experimental saponification index is 439.2 (theoretical value 440.5) and the product does not contain

 <Desc / Clms Page number 31>

 iron, chromium or other heavy metals.



    EXAMPLE: 14 -
The procedure of the Humais example is repeated taking 500 ml of 4-methyl-2-pentanone instead of toluene as solvent for the reaction. After extracting the reaction mixture
 EMI31.1
 40: 1. ' ÀiAt!;! A, VPl nn Phniie: J: 9 f: jÇll, Vf.1ot pnr c: 6ti: 17: nt.an azeotropic with 500 ml of water. Then added to the crude aqueous product
12.7 g of charcoal, after the mixture is filtered and cooled to room temperature.

   The resulting white crystals were filtered off, then dried to obtain 114 g (90.5% yield) of a compound melting at 109-109.5 C and having a saponification number of 440.8 (theoretical value). 440.5). Analysis indicates the absence of chromium and the presence of only 1 ppm of iron.



   The following examples illustrate the use of ester as a reaction medium for carrying out the invention.



    EXAMPLE¯15 -
83.0 g (0.5 mol) of industrial grade terephthalic acid and 200 g of purified bis (2-hydroxyethyl) terephthalate containing 0.83 g (1) are introduced into a 1 liter autoclave. % by weight of chromium octoate acid).



   The system is heated and stirred and after reaching a temperature of 130 ° C., an internal pressure is reached below.
0.35 kg / cm2 at the pressure gauge. At this time, 52 g (1.18 mol) of ethylene oxide are injected by means of nitrogen under pressure. The temperature rises rapidly to 138 C and the pressure up to 7.73 kg / cm2 on the manometer. After 90 minutes, the temperature returns to approximately the starting value of 130 C, while the pressure at the manometer is canceled. The autoclave and its contents are cooled to 120 ° C., then the melt reaction mixture is withdrawn and dissolved in 1000 ml of hot water.

   The aqueous solution of the crude ester is passed through a charcoal column.

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 of wood, while it is still hot, and it is cooled to separate the product. The white crystals of bis (2-hydroxyethyl) terephthalate were collected by filtration, then washed twice with cold water and dried to obtain.
315 g (90.5% yield) ester, pure, m.p. 108.5-109 C; Saponification rate 441.0 (theoretical value 440.5). Analysis indicates the presence of less than 1 ppm of chromium.



    'EXAMPLE 16 -
The process of Example 15 is repeated, but at a reaction temperature of 110 to 120 ° C. which requires a time of.
135 minutes for the total conversion of the acid.



    EXAMPLE 17 -
A series of reactions of terephthalic acid with ethylene oxide are carried out at atmospheric pressure in a conventional glass apparatus. The solvent is molten bis (2-hydroxyethyl) terephthalate. For these tests, the terephthalic acid, the catalyst (initially chromium octoate, then chromium oxide during working) and hydroxyethyl terephthalate are heated to 130-140 ° C. To this stirred suspension, ethylene oxide is added below the surface of the mixture at a rate capable of maintaining reflux. moderate. After reacting the equivalent amount of ethylene oxide and after refluxing, additional terephthalic acid, catalyst and ethylene oxide are introduced and the reaction is allowed to continue.

   We repeat the operation six times. At the end of the fifth and sixth cycles, 50 g aliquots of the reaction mixture were taken and dissolved in hot water. The solutions are filtered hot, then cooled to 5-10 ° C to isolate bis-hydroxyethyl terephthalate.



   After recrystallization from fresh water, good quality bis-hydroxyethyl terephthalate is obtained, indicating that the end product is a good solvent for the process.

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 of the reaction.



  EXAMPLE 18 -
A series of reactions are carried out using hydroxyethyl terephthalate as a solvent in a 1 liter autoclave.



  Normal hydroxyethyl terephthalate is prepared by carrying out the reaction at 110-120 ° C. using 83 g (0.5%) of terephthalic acid, 52 g (1.18 mole) of oxide. of ethylene and 0.83 g of chromium octoate in the presence of 249 g of bis-hydroxyethyl terephthalate as solvent. At the end of the reaction, as indicated by the fact that the pressure reaches a constant value, supplements of 33.2 g (0.2 mole) of terephthalic acid, 20 g (0.454 mole) of oxide are introduced. of ethylene and 0.05 g of chromic oxide as a catalyst. The reaction is repeated five times to reach the steady state. After the sixth addition, 50 g of the reaction mixture melted from the autoclave.

   The addition of fresh reagents and catalyst is then resumed and the reaction is continued four more times, withdrawing: an aliquot of 50 g between two supplies of fresh reagents. After the tenth addition, a total of five aliquots were thus collected.



   The five aliquots are processed in succession. The first is dissolved in 156 g of hot water and filtered through a Buchner funnel to remove any unchanged acid and catalyst. The filtrate is cooled to 5 ° C. and the precipitated product is collected in a cold Buchner funnel. The first filtrate is used to dissolve the second aliquot of the reaction mixture (any losses of water resulting from evaporation being compensated for by adding fresh water). The operation is repeated for the five aliquots, the filtrate from the first recrystallization of the first aliquot being used for the dissolution of the second aliquot and so on.

   The first quantity obtained of bis-hydro- terephthalate is redissolved.

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 xyethyl from the first aliquot in fresh water (corresponding to 32 g of bis-hydroxyethyl terephthalate for
100 ml of water), then the solution is cooled to 5 ° C. and the recrystallized bis-hydroxyethyl terephthalate, which constitutes the purified product, is collected. To the filtrate of this purified quantity, fresh water is added and This filtrate is used for the second recrystallization of aliquots two, four, five and so on. The average yield of purified product is used. five aliquots is 98%.



    EXAMPLE 19 -
83.0 g (0.5 mol) of isophthalic acid and 500 ml of 1,2-dichloroethane containing 0.83 g of chromium (III) octoate in the dissolved state are introduced into the autoclave. The mixture is heated and stirred and after having reached a temperature of 140 ° C., the pressure is found to rise to 3.52 kg / cm2 on a manometer.



   Then 52 g of ethylene oxide (1.18 mol) are added by means of nitrogen under pressure. The temperature reached 145 C and the pressure 8.79 kg / cm2 on the manometer. After 80 minutes, the temperature drops to 135 ° C. and the pressure to 3.16 kg / cm2 by the gauge. The autoclave and its contents are cooled to 80 ° C., then the green reaction mixture is withdrawn, to which charcoal is added, after which the mixture is filtered and cooled. By cooling to 5-10 C, white crystals of bis (2-hydroxyethyl) isophthalate are obtained.

   The solid is collected by filtration and dried so as to obtain 92 g (yield of 72.4%) of pure isophthalic ester, melting at 78-79 C, saponification number 440.5 (theoretical value 440.5). .



   EXAMPLE 20 -
A reaction of isophthalic acid with ethylene oxide is carried out under atmospheric pressure in a conventional type glass apparatus taking molten bis (2-hydroxyethyl) isophthalate as a solvent. In this case, we add
32.2 g (0.2 mol) of isophthalic acid and 0.33 g of chromium octoate

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 to 76.7 g of bis (2-hydroxyethyl) isophthalate. The mixture is heated to 100 ° C., then 20 g (0.45 mol) of ethylene oxide are slowly bubbled therein while stirring the reaction mixture, the duration of the operation being 2 hours. Then, an aliquot of the reaction mixture is titrated indicating that the conversion is 90%. The mixture is treated by cooling and dissolving in o-dichloroethane.

   The dichloroethane solution is clarified by adding charcoal and recrystallization is carried out by cooling, so as to obtain a pure product melting at 77-77.5 C.



   Although various embodiments and details of embodiments have been described to illustrate the invention, it goes without saying that the latter is susceptible of numerous variations and modifications without departing from its scope.

 

Claims (1)

CLAIM S. 1 - Process for the preparation of a 2-hydroxyalkyl ester of an aromatic polycarboxylic acid, characterized in that an aromatic polycarboxylic acid dispersed in a reaction medium is reacted in a reaction medium, which is an inert solvent normally liquid. or the ester product recycled with an alkylene oxide having 2 to 8 carbon atoms at a temperature of about 25 to 250 C in the presence of an effective amount of a trivalent chromium catalyst, the chromium catalyst being present in an amount up to about 5% by weight of the acid, and at least some amount of the 2-hydroxy ester is collected. alkyl aromatic polycarboxylic acid formed during the reaction. 2 - Process according to claim 1, characterized in that the acid comprises phthalic acid. 3 - Process according to claim 2, characterized in that the solvent is substantially immiscible with the acid <Desc / Clms Page number 36> phthalic acid and the reaction is carried out mainly on susponsion. 4 - Process according to claim 2, characterized in that the solvent is substantially miscible with phthalic acid and with the reaction product at the reaction temperature. 5 - Process according to any one of the preceding claims, characterized in that the solvent is chosen from the class formed by methyl isobutyl ketone, toluene, xylene, chlorobenzene and ethylene dichloride '. 6 - Process for preparing a bis (2-hydroxyethyl) phthalate, characterized in that ethylene oxide is reacted with a phthalic acid dissolved in recycled bis (2-hydroxyethyl) phthalate, at a temperature of 25 to 250 ° C. in the presence of an effective amount of a trivalent chromium catalyst, this chromium catalyst being present in an amount which may amount up to about 5% of the weight of the acid, and collects at least some amount of bis (2-hydroxyethyl) phthalate formed during the reaction. 7 - Process for the preparation of bis (2hydroxyethyl) terephthalate, characterized in that terephthalic acid dispersed in a normally liquid inert solvent is reacted with ethylene oxide at a temperature of about 100 to 250 C in a molar ratio of about 2.0 to 3.0 moles of ethylene oxide per mole of terephthalic acid in the presence of an effective amount of a trivalent chromium catalyst, this chromium catalyst being present in an amount up to about 5% of the weight of the terephthalic acid, and the bis (2-hydroxyethyl) terephthalate formed during the reaction is collected. 8 - Process. Following claim 7, characterized in that the molar ratio of ethylene oxy: terephthalic acid is about 2 to 2.2 moles of ethylene oxide per mole <Desc / Clms Page number 37> 'terephthalic acid. 9. A process according to claim 7 or 8, characterized in that the solvent is substantially immisible with terephthalic acid and with the terephthalate formed and this terephthalate obtained is separated from the solvent for the reaction in a solvent which dissolves a substantial amount of this terephthalate. 10 - The method of claim 7, 8 or 9 ,. characterized in that the solvent for the reaction is substantially miscible with terephthalic acid and with the terephthalate formed and the reaction is carried out at a temperature of about 100 to 200 C for about 3 minutes to 2 hours until it is substantially completed. 11 - Process according to claim 10, characterized in that the reaction mixture is refroioi or end of the reaction below about 100 C, then the solvent for the reaction is separated from the terephthalate by distillation. 12 - Process according to claim 11, characterized in that the terephthalate product is purified via an aqueous phase. 13 - Process according to claim 12, characterized. in that the terephthalate produced is recrystallized from the aqueous phase. 14 - Process according to claim 11, characterized in that the solvent for the reaction is methyl isobutyl ketone which is separated by steam stripping. 15. A process according to any one of the preceding claims, characterized in that the reaction is carried out at a temperature of 120 to 185 C. 16 - Process according to claim 1, 2 or 7, characterized in that the solvent has a boiling point of less than about 200 C. 17 - Process according to claim 16, characterized <Desc / Clms Page number 38> in that the solvent has a boiling point of about 50 to 150 C ... 18 - Process according to any one of the preceding claims, characterized in that the reaction is initiated under a pressure greater than that of the [atmosphere, but less than an absolute pressure of about 35.15 kg / cm2. 19 - Process following claim 18, characterized in that the reaction is initiated under an absolute pressure of about 7.03 to 14.06 kg / cm2.