DE1668275A1 - Process for the stabilization of organic isocyanates - Google Patents

Description

of Ii-JPEHIAL CiDSMICAL INDUSTRIES LTD., London, Great Britain

concerning

"Terfahraa for the stabilization of organic isocyanates" PRIORITY 2 ?. September 1966

The invention relates to the stabilization of organic Isocyanates by distillation of the isocyanates mentioned in the presence of stabilizers where 3S are scavengers for »free organic radicals.

3.3 it is known that organic isocyanates have a tendency to discolour on storage; you know that the Activity of such compounds during storage decreases with the course of Zgit.

Various stabilizers have already been proposed to add organic isocyanates to reduce the tendency of such compounds See discoloration when stored, decrease the right side. Stabilizing

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BATH

for example, phenols, Thioureas and certain amines. The stabilizers of this type were added to the isiocyanate after the distillation, to prevent or reduce isocyanate discoloration during storage.

It has now been found that the effects of storage on organic isocyanates both in terms of deterioration color as well as deterioration in responsiveness can be avoided or minimized if the aforementioned organic isocyanates in the presence of a cleaning agent for free organic radicals are distilled.

Thus, according to the invention, a method of srar stabilization of proposed organic isocyanates, which thereby carried out is that the organic isocyanafca in the presence of a trap · = means of distilled for free organic radicals.

Organic isocyanates obtained by the process according to the invention can be stabilized are, for example, monoisocyanates and polyisocyanates the aromatic, the aliphatic, the cycloaliphatic and the mixed-aristocratic-aUphatic series.

Examples of organic monoisocyanates are phenyl isocyanate, ec-naphthyl isocyanate, octadecyl isocyanate, o ~, m «and p-chloro

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r - ': - iors.vn.r; oci; /£.nat, Bwi.yl isocyanate and Cyclohexyllsocyanet.

Ba! Games for organic polyisocyanates are aliphatic polyi; -, oeyr; riat € !, such as z “E. Hexamethylendllsocyanatj aromatic Polyisocycnate-, ^r . * Ie ζ .B * m- and p-Phenylenedisoeyanat, Tolylen-2,4- and 2,6-6isocvanat, Dlphenylmethan-4,4 ^S -diisocyanate Chloroplieny 1 ^ nS ₁ .4- »Diisocyat.at, Naphthylen-LiS-Dilsocyanat, Diphenylen-4 _; k "-diieocyanab, ^, ^^ Dlisocyanato-J ^^ - diaieGhyldiphertyl, 3-Methyldipher.27lniefchan-> 4,4 ⁹ -diisocyanate and Diphenylätherdiisoeyanat, as well as table diisocyanates, like eg» Cyclohexane-1,4- and anafc, l -Methylcyelohexyl-2,4- and -2,6-dlisocyanate Qsmisahe therefrom as well as bis- (isoeyanatocyclohexyl) -methane. 4,4 ⁹ -Triisocyaaauodiphen./l.äfcher.

Gretnian ron or {sani; 5chen isocyanates can be sbenfells through the Process according to the invention are stabilized.

Suitable mixtures for spile are mixtures of tolylene-2,4-urd-2,5- »c! Lithium cyanate and the polyisocyanate compositions obtained by phosgenation of the mixed folytaine reaction products from formaldehyde and aromatic amines, -αλβ, for example aniline and o-tolu : ldin, can be inherited.

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The present stabilization method is then 'special advantageous when it is used with aromatic polyisocyanates, especially with tolylene-2,4- and -2,6-diisoeyanate and with Mixtures of it.

The distillation of the organic isocyanate in the presence of the scavenger for organic free radicals can occur in normal atmospheric conditions Pressure can be carried out * but it is preferably carried out under reduced pressure and in an inert atmosphere, such as SoB. in a nitrogen atmosphere. The distillation can be carried out batchwise or continuously »If the distillation is carried out continuously, i.e. under continuous supply of the material to be distilled to the Distillation vessel, then it is preferred to keep the organic free radical scavenger continuously in the distillation vessel to add at an appropriate speed »

The amount of organic free radical scavenger that occurs when method according to the invention is used, can vary widely, The amount normally used is between 0.001 and 5% by weight, preferably between 0.005 and 0.5% by weight, based on the weight of the organic isocyanate »

The one to improve the stability of the organic isocyanates

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to be used in the inventive method scavenger for Free organic radicals are organic compounds of general Formula AH, which with free radicals caused by R ° can be presented according to the process

R ° rSr-AH- »RH + A °

react, with the resulting free radical A ° In comparison is stable to R °.

Examples of scavenger for free organic radicals that can be used in the process according to the invention are, for example, phenols such as 2,4-dimethyl 6- (ei-methylcyolohexyl) phenol, 4-tert-butyl pensoatechol and propyl gallate, amines such as Diphenylamine 4-Xsopropylamlnodlphenylaniin, Phenothiazine 2.2 _i 6.6-. ^r. Tetramethylplperlti «4 ~ one> l, l-diphenyl-2- (2 ⁹ , 4 ⁹ _# 6 * ~ trlnltro <phenyl) hydrazine, hydrocarbons and quinones, such as 9,10-dihydroanthracene, 9.9 ° - Bis (fluorenylden), &> - | V-HEydroxy-3 ^e , 5 * - di (tert-butyl) phenyl-2,6-dl (tert-butyi) -benzochinon-4, -iiaethld, 9.9 ⁹ -bis (anthronyliden) and 9.9 ° -bis (anthi * onyliden) Mthane, ThIo-CKr-banilld, Bis- (2-bensthiazolyl) disulfide _rf Benzthiazolyl-2-oyclohexylsulfenamld, Bls - * (2-benzlmIdazolyl) - disulfide, zinc thiobenzoate and tin / dimethyldithlocarbamate.

The stabilizing effect of the present process has its Probably the reason for the extensive removal of harmful ones

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Impurities from the organic isocyanate and, for example not just in a mere suppression of their discoloration effect. In certain "cases, a small amount of the scavenger for free radicals, distill with the isocyanate but this is not an essential feature of the invention, and in many cases the distilled isocyanate is not a free radical scavenger present ο.

The stabilization process according to the invention gives organic ones Isocyanates, which have a reduced tendency to discolour and their susceptibility to reaction compared to the untreated Isocyanates shows a slower deterioration «The invention Process results in isocyanates with a color fastness « compared to isocyanates with color fastness additives have been maintained in accordance with the state of the art, is better. Also, the comparatively small amount added is after distillation during further processing or conversion the isocyanates advantageous.

The improvement of the color stability and the retention of the Reactivity is particularly important with polyisocyanates, e.g. Tolylene diisocyanates, of value in the manufacture of poly = urethanes find widespread usej

The invention is illustrated in more detail by the following examples.

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All parts and percentages are by weight, provided nothing else is indicated.

example 1

A mixture consisting of 80 % tolylene-2,4-diisoeyanate and 20 % tolylene-2,6-diisoeyanate was distilled and 0.01 part 2 _# 4-dimethyl-6- (et- methylcyclohexyl) phenol added. This composition is referred to as sample 1 in the following table.

100 parts of a mixture of tolylene diisocyanates as defined above, and 0.1 part of 2,4-dimethyl-6- («-methyleyclohexyl) -phenol were distilled. This sample was featured in the following table Sample 2 designated. Sample j was prepared in a similar manner, with the difference that the proportion of phenolic additive was added 0.01 part per 100 parts of ethylene diisocyanate was reduced.

Sample 4 is a sample of distilled, untreated ₉ mixed tolylenedilsoeyanates as defined above.

All samples were colorless before exposure to daylight. After exposure for a certain period of time, each became Sample compared with a color standard consisting of a solution of iron (IH) and cobalt (ΪΙΙ) salts. The degree of

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Coloring was in Eahlenwerte- from 0 (colorless) to 12 (deep yellow-brown) classified »The following table shows the determinations of the discoloration after exposure to daylight according to various Exposure times indicated.

Sample discoloration after exposure to daylight 1 day 2 days 6 days 11 days

1 <1 1 2 3 - 4

2 <1 1 1 1 - 2 2 <1 1 1 1 - 2 4 2 5 5-66

The above results illustrate the improved color stability, by treating the tolylene diisocyanate with the method according to the invention (samples 2 and 3) is obtained, and compares the color with untreated distilled JDÜsocyanafc (Sample 4) and the isocyanate that after distillation with a Addition had been treated (sample-l).

Example 2

A mixture of 100 parts of a DilaoeyanatodIphenylmethangusaroiaensosition and 0 ^ 01 part 2,4-1> lme.thyl »6» ('es »methylcyclohexyil-« " phenol was distilled. The sample 'imräe.aiifc sample 5 ■ besi "@iehnet»'

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Another sample ά & τ same Xsocyanatsusammensetzung without an added pbenollsuhen compound vmrde ;, distilled and 10 parts of distillate 0.001 part of the same additive was added phenolisehen "The sample was designated Sample 6". Another sample of the same isoeyanate composition was distilled in a similar manner without the addition of phenolic compound. This sample was named sample 7 and served as a comparison, pie samples were in sealed glass containers !! stored and exposed to diffuse! daylight. The onset of yellowing was determined as followsί

e 5 after 1 month 6th well oh 1 week 7th Within 1 day

A sample of tolylene diisocyanate before and after treatment with 0.01 Ge »« H $ 2,4-Diraethy1-6 - («s-raethy! Cyclohexyl)» phenol according to the The present invention as described in Belspisl 1 was described in bs & ug on the behavior in the trimerization to an isocyanurate polymer compared under identical conditions. The tolylene diisocyanate i was dissolved in an ester solution and kata lytlsch with a combination of a metal salt and a Phenol trimmed »After 18 hours vjaren to the non-

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treated tolylene diisocyanate 57 * 5% of the isocyanate groups reacted, while in the treated sample in the same tent 66 % of the xsoeyanate groups had reacted. Thus, the time to achieve a given isoeyanate value in the trimeric

of ethylene diisacyanate

sation by treatment according to the invention / considerably reduced " D.ho the Trlmerisat! Gas velocity of the isoyanate, the is the reactivity of the Isooyanat., is determined by the before ° lying stabilization treatment increased *

There was also the solution of the treated tolylene diisocyanate The diisocyanate polyamide solution produced is considerably paler than the one made from the untreated biisocyanate became.

Examples k

Is replaced% of compounds indicated in the following Tsbellö encryption = "then a similar increase in the Trimerisationsgeschwindlgkeit is achieved - if the phenolic compound by Oj, 01 percent in the previous example.. The results obtained are given in the following table.

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Nimble color
implemented NCO
in % close to 18 hours » Untreated sample
implemented NGO
in % after 18 hours 71.5 57.5 IChioossrbarallid 69.5 57.5 Diphenyiatnin 70.0 57.5 Ji- * Isopr opy! Amino-
ciphenylamine 16.5 57.5 π = Fropy Igallate 7 ** 1. 57.5 7, i nlcd ifouty Idithi o-
earlisroat 72.8 «57.« 5 ...

In any case, whoever the color of the isoeyanate is better than that of the untreated comparison sample.

Thus treatment with the scavengers listed above gave for free radicals according to the present method, an isocyanate with improved color fastness and improved responsiveness «

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Claims (1)

P a t. e η t ρ η s ρ r ü e h e 1, - process for stabilizing organic isocyanates, characterized in that the organic isocyanate is present in the presence an organic free radical scavenger 2, method according to claim 1, characterized in that as organic isocyanate an aromatic polyisocyanate is used will* 3c method ancii claim 2, characterized in that as. * aromatic polyisocyanate tolylene-2 ^ - or -S, 6-diisocyanate or a mixture of it is used ο ^ a / experienced according to one of the "preceding claims, characterized in that the determination is carried out under reduced pressure in an inert atmosphere" . ί> _o Method according to one of the preceding claims, characterized in that the amount used of the da3 .. Abfangraittels for free radicals EW .. {5ahen 0.001 and 5-Gei * ^ - based on the organic Isoeyahät ^ -beträgt.. 109839/1763 BAD 6 :, ¥ «rf'ihr © ii ns-sh Äasipafuijh Sv marked by the fact that the \ Tiwr <enri-2be. Hange dea AhS & ngemittel für frels radicals 0.005 rock Ö., 5 ίΐ ^ ΐί. ^ Ί "additions to the organic isocy & nätj amounts. 7 * ¥ experienced * s iiEioh. ©! Ήβη »de-r '/ orhergefeendsn- ÄfisprÜche, dadü? Oh giilcföairaetofcnöt'i that els Afrfangmiifcel for free radicals Phenol or oil aniine is used; S. Procedure naofi Aasproeh? * J dadurctt geicenrtsslkom- that , as Äbfangnitfcel filx · free Haöiltale S, 4-Ditnetby 1-6 - (<& - methyl- »phenolj Piisaotliiasln _Ä Diphenylßrntn or ^ -I will. Tß: i'. drive near eliisHä the claims "! ·· = * 6, thereby marked · = c3sß as Atj ra: "siaittel for free halves thioearbaniiid, n-Fxi-ii.i-rlgi.i.Llät or: Ji, - ikdibufcy! = äithioQarfca! n8fc used PATENTÄh4WAlTE DR.-ING. H. FfNCKE, DIPl.-ING. H. BOHR DIPU-ING. S. STAEGER BAD 109839/1763