[1]ftw 3 , 6 4 0 @ 9 6 6 @united States Patent Oflice Patented Feb. 8, 1972 2 for the producti on of organic polyisoc yanates containi ng a carbodii mideisocyana te adduct which is devoid of the foregoin - disadva nta@ges and problem s. A further object of this inventio n is to provide an improve d process for the producti on of organic polyisoc yanates containi ng a ca rbodiimi deisocyana te adduct in a single working step, that is, in a continuo us process. A still further addition al object of this inventio n is to provide an improve d process for the producti on of organic polyisoc yanates containi ng 10 a carbodii mideisocyana te adduct with catalysts that have good catalytic activity at elevated temperat ures but are complet ely inactive under the temperat ure conditio ns encount ered in storage and working up of the reaction products . Yet another object of this inventio n is to provide 15 organic polyisoc yanates containi ng a carbodii mideisocyana te adduct produce d by an improve d process, especiall y in a single working step. The forego ing object s and others which will becom e appar ent from the followi ng descri ption are accom plishe d 20 n accorda nce with the inventio n, generall y speakin g, by providin g a process for the producti on of or@- anic polyisocyanates which contain a carbodiimideisocyanate adduct by heating organic polyisocyanat eg which are free from nitrogen atoms except in the -NCO groups, that 25 is, contain nitrogen atoms only in the - NCO groups, to a temperat ure above 150' C. in the presenc e of catalytic amounts of organic compounds which contain one or more isocyanato groups and in addition biuret, urea, amido, urethane, allophanate, isocyanurate, uretdione or 30 Liretoni mine groups as catalysts, and cooling the resulting reaction products to about room temperat ure. In the process according to this invention, any suitable polyisocy anates @which are free from nitrogen, that is, those organic polyisocyan ates which do not contain any . )a nitrog en atoms apart from those in the - NCO group s, may be used either alone or in admixt ure. Any such suitabl e aliphat ic, cycloa liphati c, aromat ic or aliphat ic polyis ocyan ate may be emplo yed. Prefer ably the organi c polyis ocyan ates are aliphat ic, cycloa liphati c, aromat ic or 40 ara lip hat ic hy dr oc arb on pol yis oc ya nat es wh ich ma y 'be substitut ed by substitue nts non - reactive with - NCO groups. As example s of such suitable organic polyisoc yanates there may be mention ed the followin g: tetramet hylene diisocya nate, 1,6- hexamet hylene diisocya nate, 45 2,2, 4- tri me thy l1,6 - diis oc ya nat oh ex an e, 1,9 - no na ne diis oc ya nat e, 1,1 0- de ca me thy len e diis oc ya nat e, 1,1 2- do de ca ne diis oc ya nat e, 1,4 - cy clo he xa ne diis oc ya nat e, iso ph or on e diis oc ya nat e, man d pxyl en e diis oc ya nat es an d iso me ric mi xtu res of the se tw o diis oc y,tn ate s, 1,3 - an d 1,4 - ph en yl50 en e diis oc ya nat es, 1,3, 5- trii so pr op yl2,4 - diis oc ya nat ob en ze ne, 4- chl or o1,3 - ph en yle ne diis oc ya nat e, 2,4 - an d 2,6 - tol ue ne diis oc ya nat e an d an y mi xtu res of the se iso me rs suc h as an 80/ 20 mi xtu re of 2,4 - an d 2,6 - tol ue ne diis oc ya nat e, 4,4' -, 2,4' - an d 2,2' - dip be nyl me tha ne diis o55 cy an ate s an d an y iso me ric mi xtu res of the se dip he nyl me tha ne diis oc ya nat es, 4,4' - dip he nyl en e diis oc ya nat e, 4,4' - dip he nyl sul ph on e diis oc ya nat e, 4,4' - dic ycl oh ex yl me tha ne diis oc ya nat e, 4,4' - dip he nyl pr op an e diis oc ya nat e, 1,5 na pht hal en e diis oc ya nat e, 1,3, 5 - be nz en e trii soc ya nat e, 60 4,4' ,4"- trip he nyl me tha ne trii soc ya nat e an d the lik e. Es pe cial ly pr efe rre d are 4,4' - dip he nyl me tha ne diis oc ya nat e an d its mi xtu res wit h the 2,4' - an d 2,2' - dip he nyl me tha ne diis oc ya nat e iso me rs. Accordi ng to the inventio n, it is also possible to use 65 organic onoisoc yanates in addition to the polyisoc yanates. The followin g are named as example s of such monoiso cyanates: methylis oryanat e, ethyliso cyanate, butyliso cyanate, oetyliso cyanate, octadec ylisocya nate, allylisoc yanate, vinyliso cyanate, phenylis ocyanat e, mand ptoluene 70 isocyana te, pchlorop henyliso cyanate, pmethoxy phenylis ocyanat e, cyclohe xylisocy anate, and 2,6 - diisopro pyl 3,640,966 PROCESS FOR THE PREPARATION OF POLY ISOCYANATES WHICH CONTAIN A CARBODM,IIDEISOCYANATE ADDUCT Hans Joachim Hennig, Cologne-Stammheim, and Peter Fischer, Cologne-Flittard, Germany, assigncirs to Farbenfabriken Bayer Aktiengesellschaft, Levei.kusen Germany No Drawing. Filed Jan. 23, 1969, Ser. No. 793,547 Claims priority, application Germany, Jan. 259 1968, P 16 68 083.4 Int. Cl. C08g 22100, 22118 U.S. Cl. 260-77.5 R 9 Claims ABSTRACT OF THE DISCLOSURE Polyisocyanates containing a carbodiimide-isocyanate adduct are prepared by heating an organic polyisocyanate containing nitrogen atoms only in the isocyanato groups in the presence of a catalytic amount of a catalyst to a temperature above 150' C. and cooling the reaction product to about room temperature, wherein. said catalyst is an organic isocyanate compound containing biuret, ureal amido, urethane, allophanate, isocyanurate, uretdione or uretonimine groups in the compound. This invention relates to a process for producing polyisocyanate compositions and more particularly to a process for producing polyisocyanates which contain a carbodiimide-isocyanate adduct. It has been heretofore known that organic isocyanates can be converted into carbodiimides with elimination of carbon dioxide by prolonged heating at high temperatures. In addition, numerous catalysts are also jknown which enable organic isocyanates to be converted into carbodiimides under mild temperature conditions, such as, for example, or.-anic compounds of the elements of Main Group 5 of the Periodic Table. If, however, the isocyanate @roups of polyisoryanates are to be only partly converted into carbodiimide groups, the use of highly active catalysts is not desira:ble because the modified polyisocyanates would have insufficient stability on stora@ge owing to the continiiation of the reaction which would be extremely disadvantageous in practice. On the other hand, treating polyisocyanates without catalysts at high temperatures to effect partial conversion into carbodiimides is time consuming and y@'elds dark colored reaction products owing to uncontrollable side reactions. Therefore, there exists a recognized need for acceptable catalysts which can be used for the production of polyisocyanates containing a carbodiimide-isocyanate adduct, particularly for application in a continiious process. 'nese catalysts should have a good catalytic activity at elevated temperatures biit should be completely inactive under the temperature conditions encountered in storage and working up of the reaction products. Furthermore, these catalysts should preferably be present in liquid form in order to allow continuous dosing to be carried out easily. Another requirement for such a catalyst is that it should be substantially completely soluble in the polyisocyanate which is to'be modified because only rapid and homogeneous mlxmg ensures a controllable reaction course, especially in acontinuous process. It is also desirable that the catalyst or decomposition products of the catalyst which may be removed,with the carbon dioxide, should not interfere with the carrying out of the process. It is an object of this invention to provide an improved process for the production of organic polyisocyanates containina a carbodiimide-isocyanate adduct. It is another object of this invention to provide an improved process
[2]3 phenylisocyanate, 4 - biphenylisocyanate, decahydronaphtllalene isocyanate and the like. The catalysts which may be used according to the process of this invention may be any suitable orgaiiic compounds that contain one or more isocyanato groups and in addition biuret, urea, amido, urethane, allophanate, isocyanurate, uretdione or i-iretonimine groups. As examples of si-ich compounds there may be mentioned as representative the following examples of such catalysts: tri-(isocyanato-hexyl)-biuret, di-(isocyanato-hexyl) -urea, tri- (isocyanatohexyl) -isocyanurate, tri- (isocyanatononyl) -biuret, tri- (isocyanatododecyl) -biuret. N- (isocyanatot@-imethylhexyl)-N'-diisopropylphenyl) urea, N- (isocyanatotrimethylhexyl) -N'-diisobutyl-tirea, isocyanatoureas such as those wh;ch are obtained,. for example, by reacting 4,4'- diphenyldimethylmethane diisocyanate, isophorone diisocyanate or m- and p-xylylene diisocyanates with diisopropylaniline, diisobutylamine or 2ethylhexylamine using a 161 molar ratio, N-(isocyanatotrimethylhexyl)-2 - ethyleaproic acid amide, uretonimine compounds, such as, for example, that which is formed by addition of 1,6- hexamethylene diisocyanate to bis(diisocyanatohexyl )-carbodiimide, bis(isocyanatohexyl)uretdiore, N - isocyanatohexyl - 0 - tertiary - butylurethane or N - [isocyanato - (trimethyl) - hexyll-0isopropyl - urethane, or allophanates such as that which can be obtained by reacting 1,6-hexamethylene diisocyanate with 2-ethylhexanol using a 2:1 molar ratio and the like. The catalysts which may be used according to this invention are preferably liquid at room temperature and in gene-ral do not co-iitain slibstituents reactive with -NCO groups apart from the mentioned biuret, urea, amido, urethane and allophanate grotips. Tri-(isocyanatohexyl)-biuert is preferred as the catalyst. Accordin.- to the invention, the catalyst is added to the organic polyisocyanate in atiy catalytic quantities, generally from about 0.01 to about 10 mol percent based on the isocyanate reactant. The reaction temperature is above 150' C., generally from about 150' C. to about 300, C., preferably fro-m about 180' C. to about 220' C. The formation of the carbodiimide and simultaneous evolution of carbon dioxide takes place in an endothermic reaction. The progress of the reaction can be controlled by methods which will be obvious to those skilled in the art, for example, by continuous meastiring of the isocyanate content, or more conveniently, by measuring the amolint of carbon dioxide which has been liberated. The effectiveness of the catalysts which may be used according to the,i7ivention can be demonstrated by comparing the restilts obtained from the isocyanate determinations and measuring the amount of carbon dioxide gas evolved. Side reactions which use up isocyanate, such as, for exaniple, the formation of isocyapurates, do not occur, or only occur to a minor extent with the catalysts of this invention. The process according to the invention may be carried out batchwise but is preferably carried out contintiously. In the continuous process for preparing polyisocyanates which contain a carbodiimide-isocyanate adduct, the polyisocyanate is preferably passed through a continuous apparatus, such as, for example, a heated reaction tube or a heated reaction chamber, for example, a reaction tower, and the catalyst, which is preferably liquid and completely soluble, is continuously mixed with the polyisocyanate 1),efore the hot reaction zone is reached@ The addition of catalyst may, however, also be carried out in the heated reaction chamber. The degi-ee of conversion of the isocyatiate ,,i,otips of the polyisbcy@inate into cai,bodiimi(le gi-oiips c@in be regllIzited by the rate of flow through the apparatus, that is, 326401966 4 the time of residence in the reaction zone, the quantity of catalyst and the reaction temperatiire. The reaction prodiict is advantageously chilled to about room temperatures of less than 150' C., preferably from qbout 20' C. to about 60' C., immediately after letving the hot reaction zone. When the process is carried out continuously, this cooling can be achieved especially easily by means of a heat exchanger. The sudden cooling instantaneously brings the formation of carbodiimide to a 10 stop and the critical temperature regions in which, for exampl'e, the diisocyanates of diphenylmethane tend to form di-.ners, that is, isocyanato-uretdiones, can be bypassed so that such unwanted side reactions do not occur. Carbodiimides add to isocyanates in the cold to forni i 5 uretone imines so that polyisocyanates containing acarbodiimide-isocyanate adduct (polyisocyanates containing uretonimine groups) are obtained by the process according to the invention. The carbon dioxide which is split off is preferably cooled 20 by means of a heat exchanger and may, if desired, be freed from isocyanate which has been entrained with it by washing with an inert washing liquid, such as, for example, chlorobenzene or toluene, before the carbon dioxide is conveyed to a measuring apparatus. One may ?5 also use a washing liquid the polyisocyanate which has been liberated from the catalyst and entrained by the carbon dioxide, provided that this polyisocyanate has both a lower boiling point and a lower melting point than the polyisocyanate which is to be modified. 30 The process according to the invention may also be carried out in the presence of any suitable inert high boiling solvents such as benzene, toluene, xylene, decalin, tetradecalin chlorobenzene, o-dichlorobenzene, trichlorobenzene an@ the like. Any suitable inert solvent rnay a-Iso 35 be used for dissolving and diluting the catalyst. The inert organic solvents which may be employed in the process of this iiivention contain no groups reactive with - NCO groups. Depending on the type of the polyisocyanate which 40 is to be modified, it may be advantageous to carry out the process according to the invention under any suitable reduced pressure or under excess pressure. The products of the process are, for exaniple, viscous liquids or solid resins. They are eminently suitable for 45 the prodtiction of foam resins, especially hard foams, and have an extreinely low vapor pressure, practically no odor and are non-toxic. The produrts of the process are highly stable on storage and when liquid have practically no tendency to crystallize. They are, therefore, especially suit50 able for use in conibination with, for example, hydroxylcontaining polyesters, polyethers, polythioethers, polyacetals and polyamines according to procedures known to those skilled in the art for the production of lacquers, coatings, sheetings, adhesives, or homogeneous or porous, 55 elastic or rigid synthetic resins, in the form of tires, shaft couplings, mc)tor mounts, sound and thermal insulation and in curtain wall construction in the building industry. The invention is further illustrated but is iiot intended to be limited by the following examples in which all parts 60 and percentages are by weight unless otherwise specified. EXAMPLE I A mixture of 95 % of 4,4'-diphenylmethane diisocyanate 65 and 5 % (2.6 mol percent) of tri- (isocyanato-hexyl) -biuret which has been heated to abolit 100' C. by means of a preheater is fed by means of a pump into the bottom of a reaction tower of refined steel which is about 1.5 m. in height and has an internal volume of about 2.2 liters and 70 is filled with Raschig rings of glass and can be heated from outside to about 220' C. The reaction mixture stays in the hot reaction zone for about 3 hours, the carbon dioxide is s@lit off and is removed from the top of the reaction tower thrOLIgh a pipe. Aft.-r passing tbrough a -as 75 cooler the carbon dioxide is conducted through a meter
[3]3;640)966 5 to measure the quantity of gas evolved. The polyisocyanate which contains a carbodiimide-isocyanate adduct is removed through an overflow pipe in the upper part of the reaction tower and is chilled to about room temperature by means of a heat exchanger and trapped in a receiver. 5 The quantity of carbon dioxide split off, which is 17.7 liters (at standard temperature and pressure) per 1 kg. of reaction mixture, corresponds to conversion of about 20% of the isocyanate groups present into carbodiimide 10 groups. The product of the process is pale yellow in color and immediately after the reaction is completed it has an isocyanate content of 27.8% (calculated 27.5%) and a viscosity of 6153 CP-20- The carbodiimide groups on standing are subject to 15 further isocyanate addition, the isocyanate content being at the same time reduced and the viscosity increased. After a few days, the isocyanate content is 24.6% (calculated 24.1% 6 The product is mixed with 4,4'-diphenylmethane diisocyanate in 1: I proportions. The isocyanate content of the mixture is 29.3%; the viscosty is 45 ep.25. It solidifies at -4.5' C.; the free 1,6-hexamethylene diisocyanate content is <0.5%; the dimeric polyisocyanate content (uretdione calculated as molecular weight 500) is 0.4%. EXAMPLES 4-9 -Portions of 970 parts of 4,4'-diisocyanato-diphenylmethane are in each case treated with 30 parts (corresponding to about 3 % ) of catalyst in the form of an isocyanatourea such as that which is obtained by reacting a diisocyanate with a primary or secondary amine into 1: I molar ratio, as indicated in the following table, and heated to aboiit 220' C. The activity of the catalysts can be estimated from the time required for the liberation of 17.5 liters of carbon dioxide under normal conditions (correspoidinff to carbodiimide formation of about 20% of the isocyanate groups present). Isocyanate content oft he reaction Example Cataly st isocyanatourea Time produ ct, NO. froin diisocyanate Amino (hours) perce nt 4 -------------- 2,2,4-trimethyl1,6- Diisopropyl aiiiline ---- 2.1 24.1 diisoc yanatohexane. 5------------------- do ----------------------- Diisobutylamine ------ 13.5 24.7 6 ------------ -- 4,4'- diisocyanato- ----- do ------------ ----- 9.0 23.5 diphen yldimethylmethan e. 7 ------------ -- Isophoronediis ocyanate ---------- do ------------ ----- 9.5 23.6 8 ------------ -- MXYlylenediisocyanate ---------- do ------------ ----- 9.0 23.7 9 -------------- Comparison tests without ----------------- ------- 25.5 24.6 the addition of catalyst. EXAMPLE 2 35 In a manner analogous to Example 1, a -ixture of 95% of 4,4'-diphenylmethane diisocyantte and 2.5% of the 2, 4'-isomer and 0.5% of the 2,2'-isomer @and with 2% (I mol percent) of tri-(isocyan atohexyl)-isocyanurate is heated to about 215' C. The reaction mixture is allowed 40 to stay in the reaction chamber for about 2.5 hours and a yellow brown polyisocyanate which contains a carbodiimide-isocyanate adduct and which has an isocyanate content of 30.0 percent is obtained. The quantity of carbon dioxide eliminated per 1 kg. of mixture is 11.7 liters 45 at 25' C., that is, ab(>ut 12% of ths isocyanate groups present have been converted into carbodiimide groups. EXAMPLE 3 About 18.7 kg. per hour of 4,4'-diphenylmethane di- 50 isocyanate which is preheated to about 60' C. and therefore liquid which contains small quantities of the 2,4'- isomers and 2,2'-isomers are conveyed by means of a gear wheel pump into a reaction tank which bas a volume of about 100 liters and which is at a temperature of about 55 220' C. The reaction tank is equipped with on efficient stirrer and an overflow with siphon seal so that the effective capacity of the tank is about 70 kg., about 0.62 k g. of tri-(isocyanatohexyl)-biuret (corresponding to 4%, 1.7 mol percent, of catalyst) are fed in per hour by means 60 of a second gear wheel pump. The carbon dioxide formed is cooled to about 20' C. in a heat exchatiger and is then conducted through a washing tower through which chlorobenzene is passed to remove the isocyanate which has been carried along with it, and it then passes through a gas 65 m-,ter for measurement. About 340 liters per hour of carbon dioxide (at 20' C.) are formed. The reaction product which is continuously discharged is cooled to about room temperature by means of a cooler About 18.7 kg./hour of a pole yellow mixture of 70 polyisocyanate which contains a carbodiimide-isocyanate adduct and 4,4'-diphenylmethone diisocyanate are obtained. The isocyanate content of the reaction product is 25.0% after the product has been left standing for about 48 hours. 75 EXAMPLE 10 800 g. 4,4'-diisocyanato diphenylmethane, 200 g. 1,6hexane diisocyanate and 4 g. tris(isocvanatohexyl)-biuret are heated for 3 hours at 220' C., 20.3'1. C02 (determined at 23' C.) are split off. The isocyanate content of the reaction mixture drops from 36.9 to 25.9%. The brown coloured reaction product contains about 6% 1,6-hexane diisocyanate. EXAMPLE 11 696 g. (4 mols) 2,4-toluylene diiisocyanate are heated at 220' C. in presence of 10 g. N,N'-bis-(isocyanato dodecyl)-urea until 20% of the present isocyanate groups are transferred into carbodiimide groups under C02 evaluation. The isocyanate content of the reaction mixture is 35.6%. EXAMPLE 12 Similar as in Example 11 348 g. (2 mols) 2,4-toluylene diisocyanate and 336 g. (2 mols) 1,6-hexane diisocyanate are heated for 2.5 hours at 220' C. in presence of 4 g. N(isocyanatotrimethylhexyl) - N' - diisopropylphenylurea. After 20% of the isoryanate groups originally present have been transferred into carbodiimide groups the isocyanate content is 37%. The yield of the reaction mixture is 649 g. EXAMPLE 13 680 g. (2.72 mols) 4,4'-diphenylm-@thane diisocyanate, 300 9. 2,4-toluylene diisocyanate (1-725 mols) and 20 g. tris-(isocyanatohexyl)-biuret (0.04 mol) are heated for 3.5 hours to 220' C. 20% of the isocyanate groups originally pres6iit are by this way transferred into carbodiimide groups and 22.4 1. (determined at 23' C.) C02 are split off. The reaction n-iixture has a NCO-content of 28.7%. It is to be understood that any of the components and conditions mentioned as suitable herein can be substituted for its counterpart in the foregoing exarnples and that although the invention has been described in considerable detail in the fore,-oing, such detail is solely for the purpose of illustration. Variations can be made
[4]3)640)966 7 in the invention by those skilled in the art without departing from the spirit and scope of the invention. What is
