DE2009086A1 - Process for the preparation of pyromellitic acid diantihydride - Google Patents

Description

"Process for the production of τοη pyromellitic dianhydride"

The invention relates to a process for the production of pyromellitic dianhydride from 1,2,4,5-tetraalkylbenzene, their alkyl radicals Are methyl, ethyl and / or isopropyl radicals, by oxidation in the vapor phase, especially with air as the oxidizing agent, and is particularly concerned with cleaning or * Obtaining the fyromellitic acid lan hydride contained in the gaseous oxidation product mixture in pure form Lately the technology has been particularly in the fields tree transport, aviation, the manufacture of precision instruments and electrotechnical components developed »whereby the requirements for the heat resistance of various technical materials, such as plastics, leaks, electrical insulation films, adhesives, plasticizers and lubricants are laid. As the main starting material for manufacturing Such inert technical materials is known with preference pyromellitic dianhydride (hereinafter abbreviated to PMDA) used. In particular by folykondensatlon

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200908t - a -

Sound fMBA alt aroamtlaoaan Bl- or fetraaalnen hargootollt · Iwlylald · or folyUdaaaopyrrolono are widely ala ttaorlocoao hitaoboataadl * · electrically insulating · fabric · bakaamt, Al · la Po »tob toiba». Froifora bodies, lilatn at ", foils, la" ata and al · Üborattfo fttr oltktriaebe Brihto bann Hab ·! farvoaduai find.

Bur Ioratollung too rolylald «n odor rolylaliaaoiyrt>o> oafi la * • la AuagaBfaaatorlal ao« ar «laaa IHMt orforaartlaa, da 41 · combination by Frro« tUith «uT · (naohatooa · MjI ab odor andoro la RfDi ala odor andoro la RfDi alaoa flaoh acids considerably goatOrt bsv. boolniräohtl ^ t will , axütarordantllon fouohtigkelteenpfindlloh and storage only for one short · Zoit * !! "constantly are. therefore, these known fine PUDA-PulTor atteeen before one oie as Ausgangsaatarlal cur production cloak for hltsebeBtändiger resins may initially an expensive dehydration using JüsaigGäureanhydrid or by heating be subjected to over 200 ° C.

In addition, they contain the oxidation of 1,2,4-, 5-tetraalkyl alcohols with air in the steaming phase besides PMDA numerous by-products, v; le mono- and Dicarboxylic acids, colored tarry products and other substances. Also there is the PJIDA concentration in that from the oxidation reactor coming Cao quite small, since the oxidation with a high excess air is carried out. Therefore, one can defy

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f using intricate devices and procedures alttele of the herktiaallohen previously proposed for this purpose Isolate process only very difficult in high-purity fora. For this one For example, Xweok was proposed the following procedures

By condensing the oxidation reactor atfeBOfeaen Qeegealeohee aaa receives a faaaee product in a cooler «da · eterk colored and ait Tereohiedenen types Yen alkyl »aasolearbonic acids, with laleinic acid, quinones, tar-rich Subatansea and the same gate is polluted.

According to a »well-known process, the ··· feet · crude product is purified by means of ketones such as acetone. Ie let jedooh βehr difficult in this feiee colorless ··, obtain highly pure · HDA zn in high yield because ketones are not eelektlYcn LOeungealttel for Terunrelnlgungen. In addition, large amounts of solvent are used in this process. This solid crude product is purified in accordance with a further known purification process by baking iron using clay solvents such as water, acetic acid or the like, but this process is often afflicted with numerous weaknesses, since colored impurities cannot be completely removed, and high losses occur when it is used That is, the yield from cleaning is low, large amounts of old solvent are required and, under certain circumstances, the cleaned product can be extensively dehydrated, since FMA is formed in the case of absolute metals.
Another well-known method of cleaning is the fractionation

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Second distillation with mineral oil and prevented pressure. Bai this However, the process is difficult to obtain high-purity FMDA in high yield to get, because PMTA has a high boiling point and the Äigweohaft eu sublimate and the impurities are similar Properties never exhibit FMBA and the like. Another known method works with bit fractionated sublation. This well-known technique is an excellent method » in which the properties τοη due to oxidation in the vapor phase generated PMDA and the impurities it contains and ground it up with expert knowledge. at However, a two-stage sublimation must be carried out in this process to a first fraction and a boiled tub fraction separated from the PMDA, so that this process with the The disadvantage is that it requires high investment costs. According to another known method, the oxidation product is used with the addition of an appropriate amount of an air-water mixture or water is quenched to 150 - 75 C and the resulting PITDA powder is quenched using a SauBlereackee collected.

In this process, PMDA is a very fine powder and PMA is inevitably formed as a by-product, so that highly purified PMDt cannot be obtained with this method of operation.

The invention is therefore based on the object of a new method for the production of pyromellitic diene hydride from 1,2,4,5-tetraalkylbenzene, as alkyl radicals methyl, ethyl and / or Ieopropylresto contain, by oxidation, air in the vapor phase to create in which a highly pure PMDA in fora colorless

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Needle-sized crystals are obtained, because of their excellent resistance to hydrolysis beaitat, i.e. that I myself then hardly forms BIA, and ea thus retains its high purity when it is exposed to the atmosphere for a long period of time as handling Not very deaf and excellent as an Auagahgsfceterial suitable for the manufacture of polyimide resins which becttglioh the meohaniaohen featigkeit, the heat resistance and the Phenolic properties have excellent properties and are excellent electrical ionic materials as well as a Have good Traneparens and when staining with pigmentation substances have excellent clarity.

It has been found that this problem can be solved ₉ by keeping the gaseous reaction product mixture resulting from the oxidation for a period of time with exclusion of the ambient atmosphere at a temperature of 230-150 ° C and collecting the material which has accrued at a temperature in the above range as a product , ie duroh a process of the type mentioned above, which is characterized in that at least a 1,2,4,5-2etraalkylbenBol is oxidized with air in the vapor phase, and the pyromellitic dianhydride formed is removed from the other components of the resulting oxidation Gaa-shaped reaction product mixture (Oxydationsproduktgaegemiaoh) is separated by keeping the Oxydationeproduktgaegemiecb for a long time at a temperature of 15o - 230 ° C under the ambient atmosphere, if the main part is contained therein

Pyromellitic dianhydrida has precipitated in crystalline form « Dae fcaw. the 1,2,4 »5-Tetraalkylbengoi (e) is bssw. will be Bugaweiae under the following procedural conditions with air in the

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Vapor phase oxidizes s

Seaktionetemperätur * 350 - 55O ⁰ C; Molar ratio τοη 1,2,4,5-tetraalkylbenzene (en) to air> 1 s 100 to 1 a 1000; and space velocity * 1000 - 10 000.

A vanadium pentoxide catalyst is preferably used for the oxidation catalyst, e.g. vanadium pentoxide or a mixture of vanadium pentoxide and potassium sulfate on silicon carbide as a carrier, also 7anadium pentoxide or vanadium pentoxide and Ie-O (maximum θ % _t based on V ₂ Oc) on sintered aluminum oxide, a mixture of sintered aluminum oxide , Molybdenum and phosphorus oxides or the like.

The oxidation product gas mixture formed during the reaction is usually discharged from the reactor at a temperature of 450 to 350 ° C and contains 1.0-0.01 mol- £ FMDA, at most 0.1 mol? 6 less highly oxidized alkylbenzenecarboxylic acids, the 2,4,5-trialkylbenzoic acid, 4,5-dialkylisophthalic acids and their Anhydrides, 2,4-dialkylisophthalic acids, 2,5-dialkylterephthalic acids, Monoalkyl trimellitic acids and their anhydrides include, at most 0.05 mol-96 maleic acid homologues and quinone homologues, and at most 0.01 mol # of other by-products. The oxidation product gas mixture withdrawn from the reactor can be treated according to the invention, i.e. kept at 230 - 150 ° C, by the gas mixture withdrawn from the reactor at a temperature of 450-350 ° C. with the exclusion of the ambient atmosphere first leads through a cooler, in which it is cooled to 36Ο - 200 ° C, and then in or by means of a box-shaped, cylindrical or spherical collector gradually cools to 230-150 ° 0, preferably 200-170 ° C.

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The (purification) yield of PKDA let the better, the greater the duration of the Oxydetlonaprodukt gas mixture β in the collector. In your practice, however, the lingering time is limited by the building costs of the junker, which inevitably has to be large in volume anyway. The optimal Verwellseit la collector so fluctuates depending on the tree content of the collector and the spatial speed of the aaagsmisohes withdrawn from the reactor, but the dwell should be more than 15 seconds and preferably between 30 and 120 seconds. If one wants to separate purified PMDA in the form of large crystals and in high yield, it is very important to ensure that the oxidation product gas mixture has sufficient space so that its tree population is reduced, to report and prevent rapid cooling of the oxidation product mixture that it comes into contact with the atmosphere until PMDA has completely crystallized. Large-scale PMDA is obtained under the conditions mentioned above. For example, PKDA in the form of colorless, needle-like crystals with a diameter of 0.1-2 mm and a length of 5-50 ma in a purity of more than 98 f and in a (purification) yield of 85 - 95 % cold », laoh deaer · Ateabt looks.

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In the solution polycondensation reaction with aromatic Si. According to the experience of the invention, amines at low temperatures react much more quickly than conventional powder-form PMDl, which tends to coagulate in the viscous polycondensation solution. PMDA produced by the process of the invention can be reacted with aromatic diamines, including polyamic acids with a very high degree of polymerization, without further purification. Polyamide resins produced from polyamic acids obtained in this way therefore have excellent properties in terms of mechanical strength, heat resistance, chemical resistance and as electrical insulators, have good Iranian properties and excellent clarity when colored with pigments. The examples illustrate the invention. example 1

A tubular reactor made of corrosion-resistant steel with an inner diameter of 30 mm and a length of 750 mm is filled over a length of 400 mm with a catalyst made of vanadium pentoxide on aluminum oxide as a support and heated in a molten bath. Then a gas mixture of Burol and air in a molar ratio of 1 · 300 with a space curve of 3000 is fed into the reactor and oxidized at 460.degree. The gas mixture sucked out of the reactor «Ird is pre-cooled to 230 ° 0 and then in a collector (dimensions! 600 χ 200 χ tOO mm, capacity - 24 liters, jacket temperature 175 ° 0) in which 3 ** · ** sheets are arranged, initiated; in which pure FMM is deposited. The dwell time Id collector is 63 seconds. The exhaust gas from the collector is initially through a

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Water washing tower led and then blown off " The PMpA deposited in the collector is a mixture of needle- and rod-shaped crystals with a diameter of 0.1 up to 2 now and a length of 1 - 50 mm and a purity of 98.6 Jt. The yield, based on the im from the reactor Amount of PMDA contained in the drawn oxidation product gas mixture, is £ 90.6. The analytical data of the product obtained PUDA can be seen from Table I

PMDA
Gew.-jC Tabel I. 0 Intermediate prof
acid acids,
Wt .-) ( Tarry·
Material·,
Wt 98 * 6 PMMA ⁺ * PMA
Wt .- ^ wt .- £ 15.2
traces 0.8
0 Oxidation
product
PMDA product 84.0
1.4

Intermediate acid in the oxidation of Durol to PMDA alkylbenzenecarboxylic acids formed as intermediates

⁺ PiSMAz pyromellitic acid monoanhydride

Example 2

Am tubular reactor made of corrosion-resistant steel with An inside diameter of 25 mm is used over a length of 120 mm with a carrier made of vanadium pentoxide on aluminum oxide existing catalyst filled and heated in a molten bath, whereupon a gas mixture of durol and air in a molar ratio of 1: 300 is fed into the reactor at a space velocity of 5000 and the durol is oxidized at 435 ° C.

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Baa from the reactor withdrawn gas mixture is in a spherical, Made of glass collector fed, the internal temperature of which is kept at 175 ° C. You wipe relationships « the residence time of the oxidation product mixture in the collector and the yield of PU) A and its purity are listed in Table II.

Table II

Dwell time (sec.) Auebeut (jt) Purity (Gt * .- *) 25th 76.8 98.3 50 84.0 98.7 74 89.9 99.0 99 92.0 98.1 120 94.6 98.5 185 94.8 98.2 Example 3

In the reactor used in Example 1, Durol is oxidized under the following reaction conditions:
Molar ratio of durol to air = 1: 500;

Reaction temperature 46O ° C; Space velocity: 4000.

The oxidation product gas withdrawn from the reactor is first pre-cooled to 235 ° G and then into a 600 mm long; fed cylindrical collector with an inner diameter of 300 mm, whose temperature is kept ^{at 200 -5 0 C by means of a cooling jacket.} The residence time of the oxidation product gas mixture in the collector is 69 seconds. In the collector part

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- ■ η-

2009Ö86

calibration PSO) A yon in the form of colorless acicular crystals having a diameter O ₉ · I> 1 mm and a length of 1 »15 mm from, the sow as a product of a purity of 99» i 5 ° and in eiaer yield of 80.3 Jt is won. .

Example 4

Using the reactor of Example 2, 1,2,4 »trimethyl-5-isopropylben £ ol is obtained The molar ratio of 1,2,4-trimethyl- * 5-isopropylbenzene to air oxidizes under the following conditions

= 1 s 350 {

Space velocity 3500} Reaction temperature 440 ° 0. · ''

The oxidation product gas removed from the reactor is introduced into a spherical collector made of glass, the temperature of which is kept at 160 ° C. They dwell time is the Oxydationaproduktgasgemisohee in the collector 80 Sekunden.Im collectors FMDA deposited with a purity of 96.1 i "from which is derived from the collector in a yield of 9312 ^ ·; Example 5

£ a is the tendency to hydrolysis or the rate of hydrolysis of FMDA obtained according to Example 1 in one with moisture determined and saturated atmosphere at room temperature with that of conventional, commercially available, powdery !! FMDA compared under the same conditions. The results of these tests are shown in Table III.

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Table III

PMDA sample time (hours)

O 16 24 48 60

PMDA obtained according to Example 1 98.6 97.5 97.2 97.0 96.9 96.8

Conventional, commercial, powdery

PMDA 97.9 90.6 87.4 78.6 75.0 71.8

The values in the table indicate the purity of the PUBA in .-jC at.

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Claims (2)

Claims 1 J A method for Herateilung of Pyromellitheäuredlanhy & ricl, characterized in that at least one 1 ₉ <2.4 _S is oxidized 5-tetraalkylbenzene with air in the vapor phase, and recovering the thus formed Pyromellithsauxedianhydrid from the other constituents of the obtained in the oxidation gaseous BeaktionsproduktgemiacheeCOxydationsproduktgasgemisoh) separated by the OxydationsproduktgaBgemisoh dsr excluding Umgebungsatmosphära bim last as long at a temperature you 150 "23O ⁰ C until constitutes the main part dea in Pyi contained" © - has deposited mellithsäuredianhydrids crystalline. 2. The method according to claim 1, characterized in that the 1,2,4,5-! Üetraalkylbe33zol (s) is or are in the presence of a vanadium catalyst using a MolverMltniasea wan. to air from 1 to 100 to 1 su 1000 and a room linearity of 1000 to 10 000 b © i 350 up to 550 ° G and the oxidation product gaegemiaoh at least 15 seconds in a collector's vessel at one from 150 to 250 ° C, preferably 170 to 200 ° C. 009837/2278