DE2150639C3 - Process for the purification of triaryl phosphates - Google Patents

Description

RO
R ₁ O
R, O

P = O

(D

wherein R is an alkylaryl group and R ₁ and R _{2 are} alkylaryl or aryl groups, has been obtained, characterized in that

1. the reaction mixture at reduced pressure and at elevated temperature up to Removal of the majority of the unreacted phenols, alkylphenols and sterically distilled hindered phenols from the reaction mixture,

2. then by spraying phenol into the remaining reaction mixture during a period of time from 1 hour to 5 hours at about 200 to 300 C under reduced pressure, the sterically hindered alkylphenols drives out together with the very quickly evaporating phenol and

3. from the phenol-treated reaction mixture by fractional distillation elevated temperature under reduced pressure first phenols and then triaryl phosphates of general formula I wins.

40

2. The method according to claim 1, characterized in that the reaction mixture is triaryl phosphates contains whose alkyl groups were introduced by reacting phenol with propylene.

3. The method according to claim 1, characterized in that the phenol is injected into the reaction mixture for _{2 to 2 hours.}

50

The present invention relates to a method for purifying triaryl phosphates, the undesirable Contain iterically hindered alkylphenols.

Liquid triaryl phosphates such as tricresyl phosphate, trixylyl phosphate, mixed xylyl cresyl phosphate, and the like have because of their wide use. of triaryl phosphates as plasticizers, as gasoline additives, as functional fluids, as flame retardant additives in plastics and synthetic fibers, as oil additives, etc., of great economic value. The cost of cresols and other materials that usually make up the aryl radicals of the tertiaryl phosphates are formed, rose in recent years, as cresols, xylenols and other similar ones from Materials obtained from tar acids and petroleum tars have become scarce and difficult to manufacture. phenol is readily available at a low price; however, triphenyl phosphate is a solid that is at 4TC melts, and in many application forms cannot be used in place of liquid triaryl phosphates will.

The growing industry demand for cresols and other substituted phenols led to an increase Production of alkylated phenols used in the production of liquid triaryl phosphates will. The alkylation of phenols results in a mixture of products. For example results In the propylation of phenols, a mixture of products ("alkylates"), their main components Phenol, o-, m- and p-isopropylphenol, 2,6-, -.4-, 2,5- and 3,5-diisopropylphenol and 2,4,6- and 2,3,5-triisopropylphenol are. The relative amounts of these ingredients vary depending on the degree of propylation. The catalytic isomerization can also reduce the composition affect the proportion of ortho substitution. Various alkylated phenolic compositions such as propylated phenols, are used to convert phosphates into different grades with different Molecular weights and viscosities used. Hindered phenols, e.g. B. 2,6-Diisopropylphenol, are present regardless of the particular composition of an alkylate used. Hindered phenols create difficulties in the usual phosphorylation process. When Phenol is butylated or amylated, one obtains similar mixtures of alkylated phenols, the sterically hindered Contain phenols.

Triaryl phosphates are generally prepared by adding phosphorus oxychloride to selected phenols, such as cresols or xylenols, and the resulting reaction mixture to a temperature gradually heated from about 180 ° C. The reaction is caused by the presence of Friedel-Crafts catalysts, like aluminum chloride, accelerated. In the usual work-up, the triaryl phosphate is used distilled in a simple distillation device, the unreacted phenols being separated off as a forerun be, whereupon the triaryl phosphate is distilled off, with high-boiling in the distillation device Materials containing the catalyst residue remain. The distilled triaryl phosphate is then washed well with sodium hydroxide solution to separate the acids and phenols. The washed ones Phosphates are then often treated with activated charcoal to remove coloring materials. This general method for making triaryl phosphates is more detailed in Industrial Chemicals (2nd ed; by Faith, Keyes and Clark, John Wiley & Sons, Inc., New York, p. 777.

Alkylated phenols can be reacted _{with POCI 3} according to the method described above to form phosphates. The reaction rates of the various alkylated phenols vary with the extent and position of the substitution. The double ortho substitution of 2,6-dialkylphenol and 2,4,6-trialkylphenol makes these phenols essentially inert under normal reaction conditions due to the steric hindrance. Sonit, the unreacted portion of the phenols after phosphorylation is heavily enriched in inert components, namely the sterically hindered phenols.

Hindered phenols, such as 2,6-diisopropylphenol, 2,4,6-triisopropylphenol and similar buty-

Lated and amylated phenols are essentially in alkylphenols from a reaction mixture which is produced by

insoluble in aqueous sodium hydroxide solution and the reaction of a mixture of phenols, alkyl

remain in the tris (alkylpheny!) phosphate. The bephenols and sterically hindered alkylphenols with

treatment of tris- (a'kylphenyl) -phosphates, the ste- phosphorus oxychloride in the presence of aluminum

contain hindered phenols, with activated carbon 5 chloride as a catalyst with the formation of triaryl

catalyzes the oxidation of the sterically hindered phosphate of the general formula

Phenol to the corresponding tetraalkyldipheno-

chinone. Even without touching carbon under- RO

are the sterically hindered phenols below the usual RO-P = O (I)

Processing and storage conditions of an oxy- io '

dation. In the case of 2,6-diisopropylphenol, this is de- ^ iO

speaking diphenoquinone highly colored, and Este.,

those of mixtures of alkylated phenols, in which R is an alkylaryl group and R, and R, alkyl

2,6-DiisopropylphenoI contain, mean for many aryl or aryl groups, has been obtained

intended use, especially if it is characterized as a soft «s that one

Makers should be used too heavily colored. ,,. _D. . . ,. . ... ".

Phosphates with strong staining need to lower ^L ^ be ^the reaction mixture reduced pressure

Prices as *; nig colored esters are sold " ^nd "? ^{C1 increased} temperature bs for removal

_n · x ",, _oo ii,. ■ u ■ _ ■ · ■, ■,, -. the bulk of the unreacted phenols, lirh "nH (s ί ν ι," ^On M ⁵ 'ü ^{d llc} _u ^htem P ^find, alkyl phenols and hindered phenols Ά RI M''-^Tetra' ^ Propyld _P henochinon w. rd »distilled _from ^ _{reaction mixture,}
ί Z permanently '"Th η ^{B' eic} ^" kung, st -, _app, i _e Cend by spraying phenol in the i ™ V "■""^ ^to ^ ^{0 '8'} r ^el u ^{of the} remaining reaction mixture over a a storage Zuruckumwandlung in the stained _Zei tdauer of · /, up to 5 hours at about 200 to state. Von V. CPatea and E F.OrwolI _mc unur ve diminished! Druck die sterisch haf \ t Κ " ¹⁸ !! ^{11 Na} | f'7b ° rhydnd to the permanently- * 5 _{handicapped A} , _ky , p _heno , _e together with the Tlhllη h u ^Z , ^Ur ^ '^' ^ '" ung of Tns-; _{ehr 5chne "verda} V, _pfen de _n phenolic casts and alkylpheny) - _{P P} hos haten 2,6-Di.sopropy phenol _{3 from the mjt} p ^, _behandeiten reaction and the escaping diphenoquinone contain _{mischune by} fractional distillation be using. The Natnumborhydrid reduces the di- rhöhter _e ~ temperature under reduced pressure phenochinon to the f ^ rblosei 2 6-Dnsopropylpheno, 3o £ _{danr Tri, hosphale de.} However, this is related to the product. ' -ibt and a potential _a , | _ge my formula I wins.
Source of discoloration if the product is under

oxidizing conditions is handled. The mixture contains before the graft arylation

Treatment with sodium borohydride is expensive and time-consuming- phenol, o-, m- and p-alkylphenol, 2,6-, 2,4- and

expensive, since treatment times of several 35 3,5-dialkylphenols, 2,4,6- and 2,3,5-trialkylphenols.

Hours until treatment overnight. The distillation temperature for stage 1 is around

are borrowed. 15 mm Hg in a range of about 115 to 270 C.

U.S. Patent 3,059,015 relates to a process. Phenol is then generally obtained by spraying drive for the purification of crude phosphoric acid triaryl into the reaction mixture, which is present in the distillation ester by treatment with dilute aqueous 4 ° flask, whereupon the phenol is introduced Sodium hydroxide solution and with sodium hypochlorite solution. The- evaporated immediately or otherwise very quickly This process is, however, distilled out of the reaction mixture for the purification of triaryl and impurity phosphate esters, their oxidizable impurities, such as unreacted alkylphenols, from the strongly colored in the oxidized state, unsuitable, entrains remaining reaction mixture. The Einda the hypochlorite has an oxidizing effect. The spray of phenol takes place over a period of

According to the procedure of British patent specification '/ i up to 5 hours depending on the temperature,

883 065 is the crude unreacted phenol impurity- which can range from about 200 to 300C. the

Containing triaryl phosphate with a water pressure must be adjusted accordingly to a

a solution of a diazotized sulfonated arylamine to avoid noticeable volatilization of the phosphates,

implemented, the phenolic impurity in 5 «· Suitable conditions are a treatment during

a sulfonated azo dye is converted. 1 hour at 230 to 265 C at a pressure of

However, this method is e.g. B. to eliminate the 15 mm Hg. After the phenol introduction,

2,6-Diisopropylphenol, which remains in the presence of an amount corresponding to the equilibrium

Oxidizing agents 3,3 ', 5,5'-tetraisopropyl-4,4'-dihy-phenol in the phosphate, which after distillation

droxydiphenyl and the corresponding diphenoquinone 55 is contained in the ester, which, however, easily by a

forms, not suitable. In the case of large quantities of the subsequent washing with sodium hydroxide solution

treating substance is unlikely to be feasible to remove.

the necessary diazonium solutions are free of phenol compared to conventional spray fluids.,

to keep nitrous acid and nitrogen oxides, so that the removal of volatile impurities

that the oxidation of 2,6-diisopropylphenol can be turned to * °, various advantages. Steam is that

is expected. Are the above-mentioned Oxyda most frequently used spray fluid, but has the

Once they have arisen, they can have hydrolytic properties after use

the process of the British patent specification, the product no longer has the color after cleaning

be eliminated because their reactive 4-position corresponds to blök requirements. Phenol is more effective than one

is kiert and thus a coupling with the diazonium * 5 normal gas, such as nitrogen, since the vapor pressure of

salt cannot be done. Phenol the vapor pressure of the material to be removed

In contrast, the invention relates to a process components that are very similar, creating a powerful

results in the separation of unreacted sterically hindered stripping action. Phenol is originally in that

The system is retained and therefore does not introduce any further impurities. The phenol used is condensed and completely returned to the process, which means there are no material costs

In addition to the properties specified above, necessary for the physical separation of the volatile Impurities are highly beneficial, it has been found that the phenol surprisingly has advantages beyond a simple mechanism has. Analysis of the still pot contents before and after treatment by spraying from phenol showed a selective separation of sterically hindered phenols. Analysis of the distillate showed Surprisingly, the phenol treatment increases the amount of monoalkylphenol in the system had. These results indicate the occurrence of selective alkylation and transesterification reactions through which the sterically hindered phenols are effectively converted into sterically unhindered phenols which can easily be removed by washing with sodium hydroxide solution.

The method according to the invention is broad Extensively applicable to phosphates derived from alkylated phenols containing sterically hindered phenols.

z. B. Phenols, the alkyl groups in both ortho-Sieliungen. based on the hydroxyl group. Phenols that are sterically hindered Phenols are usually those obtained by alkylation of phenol with unsaturated hydrocarbon, such as ethylene, propylene, butylenes and amylenes were obtained. Typical alkylieries Phenol is propylated phenol. The propylation of phenol leads to a mixture of phenols, so that the aryl and alkylaryl radicals in the phosphate Would include phenyl, monopropylphenyl, dipropylphenyl and tripropylphenyl groups.

In one investigation, crude tris (isopropylphenyl) phosphate was found purified by distillation to separate most of the converted phenols, so that 555 g of the ester were obtained, which was analyzed for its propylphenol content.

The amounts of the alkylphenols (given in grains) are given in Table I. Then 75 g of phenol was injected over a period of 2 hours at 260 to 265 ° C. and at a pressure of 15 torr. The remaining ester (525 j) and the distillate (105 g) were analyzed again and the values given in Table I were found.

Table I.

o-isopropylphenol

m - \ - p -isopropylphenol

2,6-diisopiopylphenol (2,6-DlPP)

2,4-diisopropylphenol

2,4,6-tnisopropylphenol

total

Before spraying

in the still

0.66 1.04 3.50 0.22 8.80

14.22 g alkyiphenol
After spraying

by doing
Distillation flask

4.10
3.90
0.01
1.20
0.32

9.53

After

Spraying in

distillate

10.62
2.97
3.20
1.01
6.43

24.23

All in all
after
Spray

14.72
6., S 7
3.21
2.21
6.75

33.76

From the table is a remarkable increase in the unhindered phenols present in the Both the distillation flask and the distillate remain visible. The unwanted sterically bound ones Phenols were selectively separated. Transesterification as well as transalkylation are possible. If the values given in Table I are calculated> n mmol of propylene, those in the propylphenols are bound, the result is 174 mmoles before spraying and 311 mmoles after spraying, from which it can be seen that. " a transesterification has occurred. It is believed that bound (esterified). as free 2,6-diisopropylphenol is also removed. the Removal of bound 2 / i-diisoprapvlphcnoi increases the stability of the phosphate by reducing the possible dissolution of 2,6-diisopropylphenol by subsequent thermal or hydrolytic degradation of the ester.

After the spray stage, there is a small second run caught to the main extent of the withheld To remove phenol. The main fraction of the phosphate is then left behind Catalyst Rücksla-ides from the distillation flask distilled off. The crude phosphate is further processed by conventional methods, λ ic washing with sodium hydroxide solution to remove the remaining phenols present, by washing with water, by drying in a vacuum and by decolorizing with activated charcoal cleans. The product obtained in this way complies with all commercial quality regulations, including the coloration, the ear stability during storage, do Acidity, etc.

The range of the reactor temperature to be observed to carry out the desired transalkylation and conversion reactions during the expulsion

5 "iiens of the alkylphenols with the introduced phenol is about 200 to 3 (K) C. Hei lower Tcmptiatiircn are; 'ic rates of transalkylation and transesterification is undesirably low, and at much higher temperatures it results noticeable thermal degradation. Within these limits, the upper varies for performing the I'liciiolcin.injection selected temperature with the Pressure which is regulated in such a way that the proportion of phosphate which, together with the more volatile chemicals distilled, not too big. Although recovered from the condensate volatilized ester high return ratios make productivity difficult. So is at a pressure of 15 mm Hg the preferred distillation flask pressure 230 to 265 C, the spray effect under these conditions without excessive volatilization of the phosphate is effective. j) ic printing conditions are thus limited, i.e. that is, the pressure is low enough so

(IaIJ the phenol at the selected maximum temperature in the range from 2 (K) to 300 C, it vaporizes quickly and from the contents of the flask, without being removed a noticeable accumulation in the piston ci'h ;.

The preferred length of time for the injection uu! the rapid evaporation of the added phenol is ₂ to 2 hours. The time varies as a function of the heat capacity of the device, ie the speed with which the heat release capacity can supply the distillation device with the heat of vaporization required to volatilize the phenol and the simultaneously distilled alkylphenols. Times less than ₂ hours can result in very high steam speeds and excessive phosphate entrainment. Treatment times longer than 5 hours serve no useful purpose and reduce productivity.

The Phcnolmenge used for spraying will vary to some extent depending on the amount of free and bound stcrisch hindered phenols, which are to be removed from the mixed phosphate. A suitable amount is 5 to 25 percent by weight based on the crude phosphate. The preferred range is 5 to 15 weight percent based on the crude phosphate and the most preferred amount is 10 weight percent.

The facilities required are very simple; i.e., they consist of a simple distillation device, with a suitable heat source, a dip tube for injecting the phenol into the crude ester, a device to prevent entrainment in the vapor stream, a cooler, and Receiving vessel for the individual fractions is provided.

The phenol is usually in the form of a liquid with the help of a pump through the dip tube injected. If desired, phenol can be in the form of a vapor from a separate phenol vaporizer to be introduced. Such an arrangement would of course meet the heat exchange requirements of the still reduce accordingly during the introduction of the pharmaceuticals.

Although the phenol injection is usually carried out batchwise, the process can also be carried out continuously, ie the crude ester mixture can be passed through one or more columns in countercurrent to a phenol flow which is introduced at the lower part of the columns under conditions according to which the main amount of the phenol flows up the column in the form of a vapor, while the bulk of the ester is passed down through the column as a liquid phase.

Fractionation steps are not necessary and also undesirable since fractionation would tend to retain the undesired alkyl phenols.

The following examples are presented to the present invention explain further. All parts are based on weight unless otherwise specified.

M c i s ρ i e I I

The distillation device consisted of a II four-stroke flask. the iiit a dip tube for introducing ilc ¹ · ι iienols. a sampling tube connected to a high vacuum system via a sampling valve, a thermometer, a mechanical stirring device and a steam line. The steam line led to a piston to prevent entrainment.

is entrained for separation and for feeding back Spray material and then a cooler / receiver system operating at a pressure of 15 torr would. 652 g of crude propylphenyl phosphate, the AlCl 3 catalyst and over-

also contained some unreacted mixed phenols. Most of the unreacted phenol was distilled up to a pot temperature of 285 C at 15 torr removed. The contents of the still weighed 555 g at this point in time. the

»5 chromatographic analysis showed the in Table II as» Flask sample no. 1 <specified composition. Liquid phenol (75 g) was then added via the dip tube over the course of 2 hours at a flask temperature of 260 to 268 ° C. and at a pressure of 15 torr. During the phenol feed, 105 grams of distillate containing 21 weight percent phosphate and 79 weight percent mixed phenols was collected. A sample was taken from the contents of the flask and analyzed, the values in the table !! resulted in the values given as “piston sample no. 2”. The distillation was then carried out at a piston temperature of 288 ^° C. and a head temperature of 274 ° C., a mean fraction of 9 g being obtained. Product fractions totaling 394 g were then distilled over up to a flask temperature of 311 ° C. and a vapor temperature of 291 ° C. at 15 torr. The combined product fractions were analyzed by gas chromatographic analysis, contained O.22 ° / _o total phenols including alkyl phenols. 2,6-Diisopropylphenol was barely noticeable in the ChromatogrPTim, the concentration being estimated at about 10 ppm. The product was washed with a 2% aqueous sodium hydroxide solution and then with water, dried, treated with activated charcoal and filter aid and nitrated. The filtrate was almost colorless (Pt-Co color 50) (The Pt-Co color is a standard test method for determining the color of clear liquids in accordance with ASTM D-1209 [Platinum-Cobalt Seale].) The formulation of this material with Polyvinyl chloride gave a flexible film which was not discolored.

Table II Isopropylphenols,

ortho

meta
+ pare

2,6-dipropyl

2,4-dH propyl

J + 3,5-dipropyl

2,4,6-tripropyl

Piston sample no.1 Koiben sample No. 2

0.118 0.782 0.187 0.742

0.631 0.003

0.039 0.229

Q.OO79

1,588 0.061

Au-> the Fahello Il goes to the sophistication of the procedure for the separation of 2,6-diisopropylphenol and 2,4,6-triisopropylphenol. The other isoprene ! phenols, which are easily obtained by treating with Vitii '.nhvdroxydlosiing to be removed increased in concentration by the phenol treatment.

Example 2

In the device specified in Example 1, ° 7. added to the raw phosphorylation mixture. Most of the unreacted alkylphenols (54 g) were distilled to a flask temperature of 28K'C and a (Jhcr-head-'I cinpcratur win 272 C at 15 torr removed. Then 50 g Phenol in the course of 2 hours at an oil temperature from 265 to 280 C and at a pressure of 15 lorr added and 84 2 of a distillate removed. A mean cut of 11 g was then distilled off up to a column temperature of 286 ° C. Product fractions from a total of 4 '»4 g were distilled to a flask temperature of 309 C at 15 Torr. After the purification as indicated in Example 1, the product was essentially colorless (Pt Co Color 40), and the formulation of this material with polyvinyl chloride did not stain. The analysis gas chromatography showed no detectable levels Amount of 2,6-diisopropylphenol.

Comparative example A

Fin Tei ^! The same crude phosphorylation solution as that described in Example 2 was distilled according to the manner given in Example 2 with the difference that no phenol was introduced into the mixture. The product was distilled again to a flask temperature in the range from 288 to 310.degree. After purification, the product was yellow (Pt-Co 250) and contained 60 ppm 2,6-diisopropylphenol. The polyvinyl chloride formulation was discolored

Example 3

About 4990 kg of a crude isopropylphenyl phosphate mixture, which _{contained unreacted phenols and AICI 3} catalyst, was placed in a steel distillation vessel, which was supplied with a dip pipe for phenol, a steam line with a ninem separator for entrained materials and various condensate receptacles was equipped, given. The contents were freed from the main amount of the free phenols by distillation a forerun up to a flask temperature of 270 ° C. at 15 torr. The temperature was then au

ίο lowered to 265 C, and 454 kg of phenol were used in ver Run for 90 minutes at a pressure of 15 ° C and at a temperature of 230 to 265 C this dip tube added. Fs became about 680 ki K.'iidc is caught during this period The contents of the flask were then distilled again to a flask temperature of 270 ° C. at 15 torr whereupon the distillation of the product begins! vs tirde. The distillation was done to dryness guided. The distilled product was analyzed

ao and it was found that it contained 0.06 ^: ₀ total phenols but no detectable amount of 2,6-diisopropyl phenol. The product was washed with 2% sodium hydroxide solution and with water, dried and with activated charcoal and filter

3.5 help treated and filtered. The color of the Fndpro Duktes showed a Pt-Co value of 60. The test formulation for polyvinyl chloride film showed germs Discoloration.

Comparative example B

J90 about 4 kg of the same as in Example 3 schriebcnen be crude phosphate were distilled as described in the case of playing 3 manner and in the apparatus used therein ver, with the difference that no phenol in the Dcstillationseinrichtung a _s "; was leads.

The flow was removed by distillation up to Einei pot temperature of 27O ⁰ C at 15 Torr The product fraction was collected in the direction in Example 3 given way. The purified product discolored the polyvinyl chloride formulation and was found to contain 50 ppm 2,6-diisopropyl phenol.

Claims (1)

Patent claims: 1. Process for separating unreacted sterically hindered alkylphenols from a reaction mixture, made by reacting a mixture of phenols, alkylphenols and steric hindered alkylphenols with phosphorus oxychloride in the presence of aluminum chloride as Catalyst with the formation of triaryl phosphates of the general formula