DE2246920A1 - METHOD FOR PURIFYING HIGH-MELTING ISOCYANATES - Google Patents

Description

ItIPERIAL CHEMI-CAL INDUSTRIES LIMITED,
London SV 1 / ENGLAND ''''"

"Process for cleaning high-melting isocyanates"

PRIORITY ; Sept. 27, 1971 - ENGLAND

The invention relates to the purification of high-melting isocyanates by distillation and in particular αμΐ the use of a dispersion of such isocyanates as a feed to a distillation process.

Purification of isocyanates by distillation is general known. There are a wide variety of distillation processes and devices. Isocyanates are compounds with

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a relatively high boiling point, which is why they are nqrirallich distilled at a low pressure, and zv.ar because of the risk and danger of decomposition. This is particularly the case with polyisocyanates which contain two or almost isocyanate groups. In order to prevent decomposition and the risk of developing dangerous pressures, the large-scale distillation of isocyanates is normally carried out continuously with a continuous supply of isocyanates to the distillation device, so that no large concentration or large mass of isocyanate is longer Time is kept at a high temperature. In the case of isocyanates having a high melting point, this results in so far difficulties than the melting point under reduced pressure ver _T can very tightly lie at the boiling point. In order to avoid difficulties in charging a hot molten isocyanate, solutions of isocyanates have been used as starting material, but they give rise to difficulties due to solubility effects and deposition of solid material which emerges from the solution due to local cooling effects.

It has now been found that these disadvantages largely this can be eliminated if used as a starting material a dispersion of the high-melting isocyanate in an inert liquid with a higher boiling point is used.

Thus, according to the invention, a method for continuous Proposed distillation of high-melting isocyanates, which is carried out in that nan the isocyanate to a distillation device in the form of a dispersion in an inert liquid containing a has a higher boiling point than the isocyanate,, supplies.

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Ds.r present procedure is on each high melting point Isccyanate applicable, in particular to polyisocyanates. While it is useful with isocyanates that melt between 70 and 100 ° C, it is also special applicable to those with melting points above 1C0 ° C. . .

Examples of such isocyanates are naphthalene-1, ij-di- "isocrar.ac, 1,4-bis- (isocyarxatomethy'l) -" dufoif "IIIiirtdiisocyanat and trans-trans-4,4 '-diisocyanatdic3-clohe : *: ylnethan, the first three isocyanates melting points of more than 1C) O ⁰ C and the latter having a melting point vcr. 33 "C. '

The method is particularly applicable to 1,4-ice (isocyanate-ethyl) -durcl, which has a melting point of '. ^: jc ^C 'C and has a boiling point at 0.6 2131 mercury of 16G ^C C.

Any inert liquid which has a higher boiling point than the isocyanate can be used in the present process, and in particular high-boiling hydrocarbons of the aliphatic, aromatic or araliphatic series or mixtures thereof. For example, know Dcdec3 ^r lbenzol or high boiling Faraffinkc; ilen ?. ^r ac £ first mixtures are used, - iie unxtr the trademarks "ftisella oil 33" and "Risella oil 17" sold v ^: e: "den. Its particularly suitable inert liquid is ~ iiej-iiire, which comes under the common name" liquid? Faraffiii ' ¹ or "Nedisinian paraffin" known i.-t, vocei it s ~ .h a mixture of high-boiling Eohit-nvaf: £ first cf fen hsnielt. - ■ -

Liquid ■ ?: raffln has proven to be particularly useful ■ · Flü ££ igl: .it if it is -r: r. 1 ^ -Biir- (: Lc: cyanato3ieth3. ^R l} -durol is used. E; l: Lixi: e: i Dis-

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persions with up to 30 wt .-% isocyanate are produced, ' but dispersions of about 20 wt% isocyanate are less viscous and easy to handle.

It is true that dispersions from the inert liquid and from isocyanate can be obtained by direct dispersion of the solid isocyanate by physical means, but surface-active gowns can also be incorporated if necessary that are dispersants.

In the practice of the invention, a dispersion of the Ιεο-cyar-ats in the inert liquid by any of the loading. known techniques and continuously integrated into one Distillation apparatus introduced, which may be of any type normally used for continuous Distillation of isocyanate is used. It can be like that act around a cylindrical column in which the isocyanate is introduced in a hot liquid which keeps the boiling point of the isocyanate at the working pressure or it may be a thin film device g or act an evaporator, wherein the distillation off a thin film that flows down the inner walls of a container.

Difficulties are sometimes encountered in the distillation of solid isocyanates of this type as this distilled Isccyanate sublimates. Ξε has been found to largely do this can be eliminated by distilling the isocyanate into a low-boiling solvent, with the solvent in the distillation container on the back: - fluf: rehalten v / ird. In this way, the isocyanate in Reading trapped in the solvent, creating a Sublin.aticn prevents clogging which can cause blockages. By a suitable selection of the solvent the isocyanate solution formed becomes the

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± sccyanate deposited in crystalline form. In this way a crystallization stage can be incorporated into the distillation. 3in suitable solvent for use nit 1,4-bis (isocyanatomethyl) -durql is ortho-dichlorobeneol, but other chlorinated benzene sols can also be used.

The invention is explained in more detail by the following examples, wherein all parts and percentages are expressed by weight are.

example

6OC parts of crude 1,4-bis (isocyanatomethyl) durol (concentration according to isocyanate titration to a molecular weight of 244.84.3 pounds) and 2,400 parts of liquid paraffin BP were placed in a Silverson-Mischerr-Smulsifier (laboratory model, which has an emulsifying head was equipped) milled to produce a stable dispersion. This was placed in a dropping funnel provided with a bevel, which had been heated to 95 to 100 ° C. by letting steam flow through the edge! passed, and in that "he The hot dispersion was deaerated by carefully applying a vacuum. wurde- slowly to 640 parts of liquid paraffin BP out, which was stirred under a vacuum of 5 to 3. On Hg at 24C to 250 ⁰ C. The isocyanate distilled held along an electrically heated arm to the receiving container, of 1560 parts to reflux (55 to 60 ⁰ C) o-dichlorobenzene containing a to prevent constipation due to sublimation. After complete addition, the Destillen-Tenperatur during 30 minutes at 260 ⁰ C. The still was allowed to cool to 230 ° C., whereupon the pressure was increased to 40 mm Hg, so that the reflux temperature of the o-dichlorobenzene rose to 95 to 100 ° C. When all the isocyanate had been dissolved, the o-tue-

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BAD ORfGiNAL

" ⁶ " 22ΛΒ920

The chlorobenzene solution was filtered through a preheated glass funnel containing filter aid. The filtrates were cooled to below 5 ° C and a solid was obtained by filtration. The filter cake wuri- ?. Washed with 300 parts of petroleum ether at 100 to 12C ⁰ C and dried at 6C to 70 C for 24 hours under a vacuum of 15 sec: Hg. . ■■

The weight of the dried distilled. 1,4-5i £ - (is "ccyanatometfcyl) -durols was 420 parts. The Zcnzentratior.

geiza3 NCC titration was 9o, 6γ . = 81.9 % yield at 100./ ;.

example

50 parts of crude trans-trans-4 _> 4 ¹ -diisocyanato-dicyclchv: <vinethane (concentration by isocyanate nitrate with an II.G. of 262, S7.3 %) and 200 parts of liquid paraffin 3.P. 7 / are ground with a Silvers on-Mi ε ehe r-Er: ulgator (LaborEcdeli, Velches not equipped with an emulsifying head) to produce a stable dispersion. The dispersion AOirde as to 24C ^G C and 5 to 6 Em Kg distilled at 220 in a similar manner to Example 1, whereby parts have been 1GC c-dichlorobenzene used in the receiving container. The crude product was obtained by a method similar to Example 1 and, according to a determination of iscoyanate .. groups, contained trans-trans-4,4'-diisccyanato-dicyclchexylC'3u;: a ::

if

with a purity of 98.2 %.

e i 3 D i e 1

250 parts crude 1 _f 4-bic- (i3ocyana'tcnethyl) -iurol (Hen centraticn by titration on a molecular; rev / icht of 24 ^, 90.6 %), 550 parts Risolla ul 17 and 2CC parts Risülia Cl '} 'f> were equipped with a silver-scri- ^ iseli-r-krailj ^ - ~ or (laboratory model, which aix an egg emulsifier head.

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Y'sr) milled to make a stable dispersion. Di-ise was carefully deaerated under a reduced pressure of 10 zn Hg. Samples "were taken as required, around two containers of a laboratory thin-film evaporator in which the walls were certainly designed to fill and complete.

The evaporator was heated by having Thermex steam at its atmospheric boiling point. 256 "C was passed through the jacket. At a pressure of 10 EJIi ₁ Kg in the entire device, the emulsion was fed from each of the feed containers with a maximum speed which allowed the jacket temperature to be maintained.

The distillate passed through an air-cooled arm, ir. which it was partially condensed, and went cu eir.sm receptacle that is in one with a snake chilled water bath was arranged. The temperature of the Hydraulic engineering set itself at around .40 C. Under these Some Risella Cl distilled in the vertical conditions Exit from the receptacle, eliminating blockages were avoided.

790 parts of the distillate were diluted with 6C parts of o-dichlorobenzene and a solution was prepared by heating to 9C. This hot reading was passed through a preheated sintered glass funnel. 95 parts of a hot c-dichlorobenzene wash Vfurd -.i ir. di? gc-filtered liquid en incorporated. Dio Flüs-J -.?!: cit; on vairden to cool down to room temperature let ^ ssrr. and you eris ~ r-.lle vraraeii dciin by filtration abrrrr - "'no. t, Machieix. -: ie with 270 divisors. c-Dichlcrobenzene and 20c divider. Fv ~: r3 "lä ~ lisr" (Ξ.0 to 'CO ^D C) ■ r-2v: & had been seen ^ r., V.' ^ Rir.n eic ·. 24 hours at oO ^VJ C _f retry. ■

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The total of the dried distilled 1,4-bis- (isocyar.atcr: 5thyl) -durols was 169 parts (concentration by KCC-Titraticn = 100 %) = yield of 74.6> i at 100 fr.

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ORIGINAL

Claims (1)

- * 9 PA T S ^: N- TANSPR U CHBi Process for continuous distillation yqzx melting isocyanates, characterized in that the isocyanate is in the pestillationsvprrichtung in the form. introduces a dispersion in an inert liquid which has a higher boiling point than the isocyanate, 2, A method according to claim 1, characterized net gekennzeich that the polyisocyanate having a melting point ülper 7P ⁰ C. 3 ' method according to claim 2, characterized in that the isoeyanate has a Schmslaippunkt over 10C ⁰ C, "- ■'"" 4. Method according to one of the preceding claims, characterized in that the isocyanate 1,4 ^ bis- (isooy = natcisethyl) -4urQl is. 5 »Method according to one of the preceding claims, characterized in that the inert liquid a high-boiling hydrocarbon of the aliphatic, aromatic or araliphatic series or a mixture from it is. . "■.." 6. The method according to claim 5, characterized in that the inert liquid consists of liquid paraffin 3098U / 1230 ORIGINAL 7. The method according to any one of the preceding claims, characterized in that the dispersion οίε to 30 C-δ ', ν, -; - contains isocyanate. 5. Processor according to Claim 7, characterized in that it is numbered, s3ic nsx, ca3 the dispersion to £ u 20 Gev /.-; t Ieocysnat contains 9 · Method according to one of the preceding, Ar characterized in that the isocyanate in a ni boiling solvent is distilled in, which ix De ^ xillationsauinahiaebehält on Rüclcfluss ^ ehalxsr * 10. ■ The method according to claim 9 »thereby gesimsaic net that the isocyanate from 1, '+ - bis-CisocyajiatciaethvlJ-du and that the isocyanate in ortho-Dichlcrccer.coI is distilled, which is refluxed in the distillation receiver. 309814/1230 BAD ORIOiNAL