Diisocyanates having urea groups, a process for their preparation and their use in the production of polyurethanes

This invention relates to new diisocyanates containing urea groups which are liquid at room temperature or can be liquefied by heating to a temperature of up to 80.degree. C. These novel diisocyanates may be in the form of solutions in isocyanate prepolymers. The invention also is directed to a process for preparation of these new diisocyanates by the reaction of special diisocyanate starting materials and water and to their use as components for the production of polyurethanes.

BACKGROUND OF THE INVENTION 
This invention relates to new diisocyanates containing urea groups which 
are liquid at room temperature or can be liquefied by heating to a 
temperature of up to 80.degree. C. These novel diisocyanates may be in the 
form of solutions in isocyanate prepolymers. The invention also is 
directed to a process for preparation of these new diisocyanates by the 
reaction of special diisocyanate starting materials and water and to their 
use as components for the production of polyurethanes. 
It has long been known that the reaction of water with monoisocyanates 
leads to substituted ureas and the reaction of water with polyisocyanates 
leads to high molecular weight polyureas. Resinous polyureas containing 
isocyanate groups can be obtained according to U.S. Pat. No. 2,597,025 by 
using from 0.3 to 0.6 mol of H.sub.2 O per mol of aromatic diisocyanate in 
suitable solvents. It has also been disclosed that aromatic diisocyanates 
can undergo a selective reaction with water to produce low molecular 
weight diisocyanate ureas. U.S. Pat. Nos. 2,757,184; 2,757,185; and 
3,906,019 describe the reaction of 2,4-diisocyanatotoluene with water 
under suitable reaction conditions to yield the corresponding 
bis-(3-isocyanatotoly)-urea. The analogous reaction of 
2,6-diisocyanatotoluene to produce 1,3-bis-(3-isocyanatotolyl)-urea has 
been disclosed (U.S. Pat. Nos. 3,906,019 and 2,902,474). All these 
processes are carried out in solvents. The diisocyanates must be readily 
soluble in the solvents and the water added must be at least partially 
soluble. The solvent must not exert any polymerizing action on the 
isocyanate and must be free from isocyanate-reactive functional groups. 
The main disadvantage of known diisocyanates containing urea groups is that 
when produced by known processes, they invariably are obtained as solids 
of widely varying particle sizes which are infusible or can be melted only 
at very high temperatures. Thus, processing of such solids for use as 
starting materials in the production of polyurethanes, for example, 
requires their conversion into finely divided form by elaborate grinding 
processes after they have been first isolated by filtration and vacuum 
treatment to remove solvents adhering to them. Furthermore, due to the 
high melting point and low solubility of these known diisocyanates 
containing urea groups, products obtained from reactions in which they are 
used are not homogeneous and often have poor mechanical properties. Due to 
the solid state and low solubility of urea diisocyanates known in the art, 
it is difficult to observe accurate equivalent ratios of isocyanate groups 
to isocyanate-reactive groups when processing them, since the 
ureadiisocyanate particles often react only on the surface so that the 
reaction products from an envelope enclosing unreacted urea diisocyanate. 
However, diisocyanates which contain urea groups are valuable starting 
materials for the production of polyurethanes since the urea segments 
incorporated in the end products often improve the mechanical properties 
of the polyurethanes. 
Objects of the present invention are to provide new urea diisocyanates for 
the production of polyurethanes having improved mechanical properties, to 
overcome the disadvantages of the urea diisocyanates known in the art, and 
to provide a process for the preparation of these urea diisocyanates which 
does not have the disadvantages of processes known in the art. 
These objects surprisingly can be achieved by reacting certain 
sulfur-containing diisocyanates with water to produce the corresponding 
diisocyanates containing urea groups. 
DESCRIPTION OF THE INVENTION 
The present invention relates to diisocyanates containing urea groups which 
are liquid at room temperature or which can be liquefied by heating to a 
temperature of not more than 80.degree. C., corresponding to the formula: 
##STR1## 
wherein 
m represents a whole or fractional number (on statistical average) of from 
0 to 3, preferably 0; 
R.sub.1 represents hydrogen, an alkyl group having from 1 to 4 carbon atoms 
or an alkylthio group having from 1 to 4 carbon atoms; and 
R.sub.2 represents a phenylene group optionally substituted by alkyl groups 
having from 1 to 4 carbon atoms or by an alkylthio group having from 1 to 
4 carbon atoms, or it represents a linear or branched chain aliphatic 
hydrocarbon group having from 2 to 12 carbon atoms, at least 2 carbon 
atoms being situated between the nitrogen atom and the sulfur atom. 
The invention also relates to mixtures which are liquid at room temperature 
or can be liquefied by heating to a temperature of not more than 
80.degree. C. comprising from 5 to 50% by weight of the diisocyanates 
containing urea groups and isocyanate prepolymers, which are liquid at 
room temperature or can be liquefied by heating to a temperature of not 
more than 80.degree. C., the prepolymers corresponding to the formula: 
EQU D--OCO--NH--A--NCO).sub.n 
wherein 
n represents a whole or fractional number (on statistical average) of from 
2 to 4; 
A represents a residue of the type obtained by the removal of the 
isocyanate groups from an organic diisocyanate; and 
D represents a residue of the type obtained by the removal of the hydroxyl 
groups from an n-functional polyhydroxyl compound having a molecular 
weight in the range of from 500 to 8,000 or by the removal of the hydroxyl 
groups from a mixture of such polyhydroxyl compounds. 
It is preferred to use isocyanate prepolymers of the specified formula 
wherein 
n represents 2; and 
A represents an aliphatic hydrocarbon group having from 6 to 12, preferably 
6 carbon atoms, where at least 6 carbon atoms are situated between the 2 
nitrogen atoms, a cycloaliphatic hydrocarbon group having from 4 to 15 
carbon atoms, an aromatic hydrocarbon group having from 6 to 15 carbon 
atoms, a xylylene group or a group of the formula: 
##STR2## 
in which 
R.sub.1.sup.' represents hydrogen; and 
R.sub.2.sup.' represents a polymethylene group having from 2 to 6 carbon 
atoms or a 1,4-phenylene group. 
The mixtures of the diisocyanates containing urea groups and the isocyanate 
prepolymers preferably are liquid solutions, pastes or solid solutions 
which can be liquefied by heating to not more than 80.degree. C. 
The present invention also relates to a process for the preparation of 
these new diisocyanates containing urea groups comprising reacting 
diisocyanates of the formula: 
##STR3## 
wherein R.sub.1 and R.sub.2 are as defined above with from 0.4 to 0.8 mol 
of water per mol of diisocyanate, or with a corresponding quantity of a 
compound from which water is split off. The resulting diisocyanate 
containing urea groups optionally is subsequently dissolved in from 50 to 
95% by weight, based on the whole mixture, of an isocyanate prepolymer of 
the type defined above. 
Additionally, the present invention relates to the use of these new 
diisocyanates, optionally dissolved in isocyanate prepolymers, as starting 
components for the production of polyurethanes by the isocyanate 
polyaddition process. 
Preparation of the diisocyanates used as starting material for the process 
of the invention is carried out as described in German Patent Application 
No. P 29 16 135.1 by phosgenation of diamines of the formula: 
##STR4## 
wherein R.sub.1 and R.sub.2 have the definitions above. 
Diamines containing thioether groups which may be used as starting 
materials for the preparation of corresponding diisocyanates can be 
obtained by methods known in the art. Thioether group-containing amines 
having an aliphatically bound amino group, for example, may be obtained by 
a process analogous to that described in German Offenlegungsschrift No. 27 
34 575 in which the corresponding sodium aminothiophenolates of the 
formula: 
##STR5## 
are reacted with the appropriate chloramines of the formula: 
EQU Cl--R.sub.2 --NH.sub.2 
wherein R.sub.2 is an aliphatic group. The above-mentioned sodium 
thiophenolates are readily obtained by alkaline saponification of the 
corresponding benzothiazoles. 
Diamines containing exclusively aromatically bound amino groups and 
thioether groups may be obtained, for example, by the reaction of known 
o-amino substituted sodium-thiophenolates with the appropriate 
p-nitrochlorobenzenes of the formula: 
EQU Cl--R.sub.2 --NO.sub.2 
to produce intermediate compounds containing an amino group and a nitro 
group, followed by reduction of the nitro group to the amino group, for 
example, by means of zinc/hydrogen chloride or the use of Raney nickel as 
catalyst. The preparation of the intermediate compounds has been outlined, 
for example, in J. Chem. Soc. London, 1930, 180 et. seq. 
Another example of a method for the preparation of thioethers containing 
two aromatically bound amino groups is the reaction of the last-mentioned 
p-nitrochlorobenzenes with sodium sulfide to form the corresponding 
p-aminothiophenolates of the formula: 
EQU H.sub.2 N--R.sub.2 --SNa 
followed by their condensation with o-chloronitrobenzenes of the formula: 
##STR6## 
which is again followed by reduction to an amino group of the nitro group 
still present. Preparation of an intermediate stage containing an amino 
group and a nitro group carried out on this principle has been described, 
for example, in J. Chem. Soc. London, 1930, 180. 
Finally, the diamines containing thioether groups and two aromatically 
bound amino groups may also be obtained by reaction of the corresponding 
o-nitrothiophenolates with the appropriate p-nitrochlorobenzenes or by 
reaction of the corresponding p-nitrothiophenolates with 
o-nitrochlorobenzenes to produce the intermediate stage containing two 
nitro groups, followed by reduction of the nitro groups of the 
intermediate stage to amino groups. The preparation of the intermediate 
compound obtained in this method has been described, for example, in 
Journal of the American Chemical Society 45, 1399 et. seq. 
The following are examples of suitable diamines: 
2-(2-aminoethylthio)-aniline; 2-(6-aminohexylthio)-aniline; 
2-(12-aminododecylthio)-aniline; 2-(2-aminoethylthio)-5-methoxy aniline; 
2-(2-aminoethylthio)-5-chloro aniline; 2-(6-aminohexylthio)-5-ethylsulfono 
aniline; 2,4'-diaminodiphenyl sulfide; and 
2,4'-diamino-3'-ethylthiodiphenyl sulfide. 
Phosgenation of the diamines exemplified above to the corresponding 
diisocyanates is carried out by known methods, preferably using a suitable 
auxiliary solvent such as chlorobenzene at a temperature of from 
-20.degree. C. to 130.degree. C. Suitable methods of phosgenation have 
been described, for example, in High Polymers XVI "Polyurethanes Chemistry 
and Technology", Part I, Interscience Publishers, New York, London 1962, 
pages 17 et seq. 
The diisocyanates obtained by the phosgenation reaction naturally 
correspond in structure to the diamines used as starting materials. 
The process of the invention may generally be carried out according to one 
of the following two embodiments. 
In the first embodiment, the sulfur-containing starting diisocyanates are 
used in the process of the invention as solutions of from 10 to 90% by 
weight, preferably from 30 to 70% by weight, of sulfur-containing 
diisocyanates in an inert solvent and reacted at a temperature of from 
25.degree. to 100.degree. C., preferably from 40.degree. to 70.degree. C., 
with from 0.4 to 0.8 mol, preferably from 0.5 to 0.6 mol, of water or a 
corresponding quantity of a compound releasing water, per mol of starting 
diisocyanate. The solution of starting diisocyanate is preferably 
introduced into the reaction vessel first and then the water of compound 
which splits off water is added to the solution. The progress of the 
reaction can easily be followed and controlled by determination of the 
volume carbon dioxide released. The solvent may be removed after the 
reaction, for example, by distillation. If the solvent is removed by 
distillation, the compounds of the invention are contained in the 
distillation residue. The following are examples of suitable inert 
solvents: acetone, methylethyl ketone, methyl isobutyl ketone, dioxane, 
cyclohexanone, ethylacetoacetate and acetyl acetone. 
Examples of suitable compounds from which water can be split off include: 
formic acid, tertiary alcohols such as tertiary butanol and organic and 
inorganic compounds containing water of crystallization such as pinacol 
hexahydrate, chloral hydrate or sodium sulfate decahydrate. However, 
liquid water preferably is used rather than compound which split off 
water. 
In a second embodiment, the starting diisocyanate containing sulfur is 
mixed with an isocyanate prepolymer of the previously specified formula: 
EQU D--OCO--NH--A--NCO).sub.n 
which should be either liquid at room temperature or capable of being 
melted by heating to not more than 80.degree. C. The sulfur-containing 
diisocyanate and the prepolymer are used in such proportions that the 
overall mixture contains from about 5 to 50% by weight, preferably from 5 
to 25% by weight of the starting diisocyanate. Water or a water releasing 
compound is then added under vigorous mixing conditions to the resulting 
mixture in an amount corresponding to from 0.4 to 0.8 mol of water, 
preferably from 0.5 to 0.6 mol of water, for each gram-equivalent of 
isocyanate groups in the sulfur-containing diisocyanate. The reaction 
mixture is kept within the temperature range of from 25.degree. to 
100.degree. C., preferably from 40.degree. to 70.degree. C. The progress 
of the reaction can be followed volumetrically from the quantity of carbon 
dioxide liberated. Solutions of the diisocyanates containing urea groups 
of the invention is the isocyanate prepolymer are directly obtained by 
this method. 
Polyols of the formula: 
EQU D(OH).sub.n 
wherein D has the same definition as above, used for the preparation of the 
isocyanate prepolymers may be polyesters, polyethers, polythioethers, 
polyacetals, polycarbonates or polyester amides having a molecular weight 
in the range of from 500 to 8,000, preferably from 1,000 to 3,000, and 
having from 2 to 4, preferably 2 hydroxyl groups, such as those known for 
the production of both noncellular and cellular polyurethanes. It is 
preferable to use the corresponding polyester polyols or polyether 
polyols. 
Examples of suitable polyesters containing hydroxyl groups include the 
reaction products of polyhydric, preferably dihydric alcohols, optionally 
with the addition of trihydric alcohols, and polybasic, preferably dibasic 
carboxylic acids. Instead of free polycarboxylic acids, the corresponding 
polycarboxylic acid anhydrides or corresponding polycarboxylic acid esters 
of lower alcohols or mixtures thereof may be used for preparing the 
polyesters. The polycarboxylic acids may be aliphatic, cycloaliphatic, 
aromatic and/or heterocyclic and they may be substituted, e.g., by halogen 
atoms, and/or unsaturated. Examples of suitable polycarboxylic compounds 
include: succinic acid; adipic acid; suberic acid; azelaic acid; sebacic 
acid; phthalic acid; isophthalic acid; trimellitic acid; phthalic acid 
anhydride; tetrahydrophthalic acid anhydride; hexahydrophthalic acid 
anhydride; tetrachlorophthalic acid anhydride; endomethylene 
tetrahydrophthalic acid anhydride; glutaric acid anhydride; maleic acid; 
maleic acid anhydride; fumaric acid; dimeric and trimeric fatty acids such 
as oleic acid optionally mixed with monomeric fatty acids; dimethyl 
terephthalate and terephthalic acid-bis-glycol esters. The following are 
examples of suitable polyhydric alcohols; ethylene glycol; propylene 
glycol-(1,2) and -(1,3); butylene glycol-(1,4) and -(2,3); 
hexanediol-(1,6); octanediol-(1,8); neopentylglycol; cyclohexanedimethanol 
(1,4-bis-hydroxymethylcyclohexane); 2-methyl-1,3-propanediol; glycerol; 
trimethylol propane; hexanetriol-(1,2,6); butanetriol-(1,2,4); 
trimethylolethane; diethylene glycol; triethylene glycol; tetraethylene 
glycol; polyethylene glycols; dipropylene glycol; polypropylene glycols; 
dibutylene glycol and polybutylene glycols. Polyesters of lactones such as 
.epsilon.-caprolactone or hydroxycarboxylic acids such as 
.omega.-hydroxycaproic acid may also be used. 
The polyethers which may be used in the present invention which have from 2 
to 4, preferably 2 hydroxyl groups are generally known and are prepared, 
for example, by self-polymerization of epoxides such as ethylene oxide, 
propylene oxide, butylene oxide, tetrahydrofuran, styrene oxide or 
epichlorohydrin, e.g., in the presence of BF.sub.3. The polyethers also 
may be obtained by the addition of these epoxides, optionally as mixtures 
or successively, to starting components having reactive hydrogen atoms, 
such as water, alcohols or amines. Examples of suitable starting 
components include ethylene glycol, propylene glycol-(1,3) or -(1,2), 
trimethylolpropane, 4,4'-dihydroxydipheyl propane, aniline, ammonia, 
ethanolamine or ethylene diamine. It is often preferred to use polyethers 
which contain predominantly primary OH groups (i.e., up to 90% by weight 
based on all the OH groups present in the polyether). Polyethers modified 
with vinyl polymers, e.g., the compounds obtained by the polymerization of 
styrene and acrylonitrile in the presence of polyethers (U.S. Pat. Nos. 
3,383,351; 3,304,273; 3,523,093; and 3,110,695 and German Pat. No. 
1,152,536) are also suitable. 
Examples of suitable polythioethers include the self-condensation products 
of thiodiglycol and/or the condensation products of thiodiglycol with 
other glycols, dicarboxylic acids, formaldehyde, aminocarboxylic acids or 
amino alcohols. The products obtained are polythio mixed ethers, polythio 
ether esters or polythio ether ester amides depending on the 
co-components. 
Suitable polyacetals include, for example, the compounds which can be 
prepared from glycols such as diethylene glycol, triethylene glycol, 
4,4'-dioxethoxydiphenyl dimethyl methane, hexanediol and fromaldehyde. 
Suitable polyacetals for the purpose of the present invention may also be 
prepared by the polymerization of cyclic acetals. 
Suitable polycarbonates having hydroxyl groups which may be used are 
generally known. Examples include those polycarbonates which can be 
prepared by the reaction of diols such as propanediol-(1,3), 
butanediol-(1,4) and/or hexanediol;-(1,6), diethylene glycol, triethylene 
glycol or tetraethylene glycol with diarylcarbonates such as 
diphenylcarbonate, or with phosgene. 
Polyhydroxyl compounds already containing urethane or urea groups and 
modified or unmodified natural polyols such as castor oil may be used. 
Representatives of these compounds which may be used in the present 
invention have been described, for example, in High Polymers, Vol. XVI, 
"Polyurethanes, Chemistry and Technology" by Saunders Frisch, Interscience 
Publishers, New York, London, Volume I, 1962, pages 32-42 and pages 44-54 
and Volume II, 1964, pages 5-6 and 198-199 and in Kunststoff-Handbuch, 
Volume VII, Vieweg-Hochtlen, Carl-Hanser-Verlag, Munich, 1966, e.g., on 
pages 45 to 71. Mixtures of these compounds may also be used, such as 
mixtures of polyethers and polyesters. 
The polyester diols and polyether diols corresponding to the above 
description are preferred. 
Examples of suitable diisocyanates corresponding to the formula: 
EQU A(NCO).sub.2 
wherein A represents a residue of the type obtained by the removal of the 
isocyanate groups from an organic diisocyanate for the preparation of the 
isocyanate prepolymers include: tetramethylene diisocyanate; hexamethylene 
diisocyanate; 1,12-dodecane diisocyanate; cyclobutane-1,3-diisocyanate; 
cyclohexane-1,3- and -1,4-diisocyanate and mixtures of these isomers; 
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane; 2,4- and 
2,6-hexahydrotolylene diisocyanate and mixtures of these isomers; 
hexahydro-1,3- and/or -1,4-phenylene diisocyanate; perhydro-2,4'- and/or 
-4,4'-diphenylmethane diisocyanate; 1,3- and 1,4-phenylene diisocyanate; 
2,4- and 2,6-tolylene diisocyanate and mixtures of these isomers; diphenyl 
methane-2,4'- and/or -4,4'-diisocyanate; naphthylene-1,5-diisocyanate; 
2,4'-diisocyanatodiphenyl sulfide; 2-(.omega.-isocyanatoalkylthio)-phenyl 
isocyanates; polyisocyanates having carbodiimide groups as described in 
German Pat. No. 1,092,007; and the diisocyanates described in U.S. Pat. 
No. 3,492,330. Mixtures of these diisocyanates may also be used. 
Generally, it is particularly preferred to use diisocyanates such as 2,4- 
and 2,6-tolylene diisocyanate and any mixtures of these isomers ("TDI"), 
and 2,4'-and/or 4,4'-diisocyanatodiphenyl methane. 
According to a preferred variation of the second embodiment of the process 
of the invention, the isocyanate prepolymers are prepared in situ by 
reaction of the polyols of the type exemplified with an excess of the 
sulfur-containing diisocyanate used as a starting material. The 
sulfur-containing diisocyanate is used in such an excess over the quantity 
required for NCO/OH equivalent ratio of 2:1 that solutions of excess 
sulfur-containing diisocyanate in the developing isocyanate prepolymer 
containing from about 5 to 50% by weight, preferably from 5 to 25% by 
weight, of the free, starting sulfur-containing diisocyanate are obtained 
directly. In this preferred variation, the group A in the formula for the 
isocyanate prepolymer corresponds, of course, to the group obtained by 
removal of the isocyanate groups from the sulfur-containing diisocyanate 
of the specified formula used as starting material. The water or 
water-releasing compound may then be addd as in the second embodiment 
previously described. 
The urea diisocyanates of the present invention are either liquids at room 
temperature or in many cases, substances which are pasty at room 
temperature, but which can be liquefied by simply heating to a temperature 
of not more than 80.degree. C. The physical states of the compounds of the 
invention depend mainly on the value of the index m for the urea 
diisocyanate. The particularly preferred urea diisocyanates of the present 
invention in which m=O are generally liquid at room temperature. The value 
for m depends on the molar ratio of isocyanate/water used in the process 
of the invention. Such compounds in which m=O are obtained in a 
substantially selective reaction when 0.5 mol of water is used per 
gram-equivalent of isocyanate groups in the diisocyanates used as a 
starting material in the process of the invention. This selectivity of the 
reaction is due to the selective reactivity of the isocyanate groups in 
the starting diisocyanates. If water is not used in excess, the aromatic 
isocyanate group in the ortho position to the sulfur atom is generally the 
first to react. 
Since isocyanate prepolymers which are liquid at room temperature or which 
can be melted by heating to 80.degree. C. are used in the second 
embodiment of the process of the invention, solutions of the urea 
diisocyanates in these isocyanate prepolymers are also liquid at room 
temperature or can be liquefied by simply heating to not more than 
80.degree. C. Such systems can, of course, also be obtained by mixing 
appropriate quantities of separately prepared urea diisocyanates of the 
invention with the isocyanate prepolymers. 
The quantity of free, unreacted sulfur-containing diisocyanate present in 
the compounds of the present invention or their solutions in isocyanate 
prepolymers is generally less than 0.6% by weight if at least 0.5 mol of 
water is used per gram-equivalent of isocyanate groups of the 
sulfur-containing diisocyanates used as starting material. 
It would be possible in principle, although it is less preferred, to use 
isocyanate prepolymers which melt above 80.degree. C. for the process of 
the invention. In that case, it is advisable to use compounds which split 
off water, such as pinacol, hexahydrate, instead of water itself, and to 
add inactivating acidic compounds such as phosphoric acid, toluene 
sulfonic acid or benzyl chloride in a quantity of from 0.01 to 0.1% by 
weight based on the reaction mixture to prevent side reactions such as 
biuret formation. These compounds are also necessary when tertiary butanol 
is used as a source of water, to reduce the decomposition temperature of 
the tertiary butyl urethane originally formed. Solutions of urea 
diisocyanates of the present invention which can be melted by heating to a 
temperature of not more than 80.degree. C. are, in many cases, also 
obtained when the isocyanate prepolymers melt at a temperature above 
80.degree. C. 
Compounds known in the literature to accelerate diisocyanate addition 
reactions, such as tertiary amines or organometallic compounds, are 
generally avoided when carrying out the process of the present invention, 
in order to prevent the formation of high molecular weight polyureas which 
contain substantially no isocyanate groups. 
The urea diisocyanates of the invention are particularly valuable starting 
materials for the preparation of polyurethanes. Polyurethane elastomers 
produced from them have particularly interesting mechanical properties due 
to the urea segments contained in them. At the same time, due to their 
liquid consistency at a temperature below 80.degree. C., the compounds of 
the present invention may be handled easily. Yet, they are physiologically 
harmless due to their low vapor pressure. 
The urea diisocyanates of the invention and their solutions in the 
isocyanate prepolymers are particularly suitable for the production of 
polyurethane elastomers. 
When the urea diisocyanates of the invention are used in the production of 
polyurethane elastomers, the solutions of the new compounds in isocyanate 
prepolymers, for example, may be reacted by a known method with known 
chain lengthening agents. The equivalent ratio of isocyanate groups to 
isocyanate-reactive groups in the chain lengthening agents is generally in 
the range of from 0.9:1 to 1.2:1, most preferably from 1:1 to 1.1:1. 
The chain lengthening agents used may be, for example, water, simple 
glycols having a molecular weight of from 62 to 500 or organic diamines 
containing two primary and/or secondary amino groups having a molecular 
weight of from 62 to 500. Hydrazines may also be used as chain lengthening 
agents. Examples of suitable organic diamines include: aliphatic diamines 
such as ethylene diamine and hexamethylene diamine; and cycloaliphatic 
diamines such as 4,4'-diaminodicyclohexyl methane or 
1-methyl-2,4-diaminocyclohexane. Aromatic diamines are preferred and 
include such diamines as: bis-anthranilic acid esters according to German 
Offenlegungsschrifts Nos. 2,040,644 and 2,160,590; 3,5- and 2,4- 
diamino-benzoic acid esters according to German Offenlegungsschrift No. 
2,026,900; the diamines having ester groups described in German 
Offenlegungsschrifts Nos. 1,803,635; 2,040,650; and 2,160,589; 
3,3'-dichloro-4,4'-diaminodiphenyl methane; 
3,3'-dithioether-4,4'-diaminodiphenyl methane; phenylene diamines; 
tolylene diamines; 3,5-diethyl-2,4-diaminotoluene; 4,4'-diaminodiphenyl 
methane; 2,2'-diaminodiphenyl sulfide; 2,4'-diaminodiphenyl sulfide and 
4,4'-diaminodiphenyl sulfide. 
Examples of suitable glycols which may be used as chain lengthening agents 
include: ethylene glycol; propylene glycol-(1,2) and -(1,3); 
butanediol-(1,4) and -(2,3); pentanediol-(1,5); hexanediol-(1,6); 
octanediol-(1,8); neopentyl glycol; 1,4-bis-hydroxy methyl cyclohexane; 
2-methyl-1,3-propanediol; butenediol; butynediol; monochlorohydrin; 
glycerol-monoalkyl- or -mono-aryl ethers; xylylene glycols; and the 
Diels-Alder addition product of butenediol and anthracene or 
hexahydro-pyrocatechol. 
When the chain lengthening agents are reacted with the urea diisocyanates 
of the invention or their solutions in isocyanate prepolymers, all the 
free isocyanate groups react smoothly whereas when solid urea 
diisocyanates or their suspensions are used, the reaction depends to a 
great extent on the particle size of the urea diisocyanates and the 
solubility of the reaction products of the solid urea diisocyanates with 
the diol or diamine in the isocyanate prepolymer. Even minute particles of 
urea diisocyanates behave as fillers in that the polyurethane or polyurea 
formed on the surfaces of the particles by the reaction with chain 
lengthening agents encapsulates unreacted urea diisocyanate. This behavior 
as fillers is a serious disadvantage in polyurethane production since it 
greatly reduces the mechanical and dynamic properties of the polyurethanes 
and forms weak zones in the polyurethanes which tend to cause breaking 
under loads at these zones. The relatively high molecular weight 
polyhydroxyl compounds mentioned as examples for the production of the 
isocyanate prepolymers may, of course, also be included when the new urea 
diisocyanates are used for the production of polyurethanes. 
When the new diisocyanates of the present invention are used for the 
production of polyurethanes, in particular polyurethane elastomers, known 
auxiliary agents and additives such as plasticizers, dyes and fillers may 
also be added. Phthalic acid esters and organic sulfonamides, for example, 
are suitable plasticizers. It is often particularly advantageous to use 
plasticizers which contain sulfur, such as methylene-bis-thioglycolic acid 
butylester. 
Fillers and pigments such as titanium dioxide, silicon dioxide, bentonite, 
calcium silicate and carbon black may also be used. They may be direcly 
incorporated in the higher molecular weight polyhydroxyl compound or in 
the isocyanate prepolymer. 
The polyurethane elastomers produced using the process of the invention 
have excellent mechanical properties, improved high temperature 
characteristics and excellent resistance to organic solvents and oils. 
This enables them to be used in a wide variety of fields, for example, as 
roller cloths, elastic parts for machines, seals, buffers, bellows, 
linings for ball mills, shoe soles, gear wheels and automobile tires.

The following examples illustrate the invention. All quantities are in 
parts by weight or percentages by weight unless otherwise indicated. 
Examples 1(a) through 1(i) illustrate the preparation of liquid urea 
diisocyanates containing sulfur. 
EXAMPLE 1(a) 
1.8 g of water in 50 ml of anhydrous acetone are added dropwise within 15 
minutes to 53.6 g (0.2 mol) of 2,4'-diisocyanatodiphenyl sulfide in 200 ml 
of anhydrous acetone at 50.degree. to 55.degree. C. Evolution of gas 
begins instantly. The mixture is stirred at 50.degree. to 55.degree. C. 
until no more gas evolves. Acetone is removed under vacuum. A liquid which 
is highly viscous at room temperature and has the chemical composition 
corresponding to the following formula is left behind: 
##STR7## 
Isocyanate content (calculated) 16.5%. 
Isocyanate content (found) 16.25%. 
The following liquid urea diisocyanates containing sulfur are synthesized 
by methods analogous to that of Example 1(a) (see Table). 
__________________________________________________________________________ 
% Isocyanate 
content 
Diisocyanate Urea Diisocyanate (Calc.) 
(Found) 
__________________________________________________________________________ 
(b) 
2,4'-diisocyanato- 3'-ethyl-diphenyl sulfide 
##STR8## 14.8 
14.65 
(c) 
2,4'-diisocyanato- 3'-ethyl thio- diphenyl sulfide 
##STR9## 13.3 
13.35 
(d) 
2,4'-diisocyanato- 5-ethyl-diphenyl sulfide 
##STR10## 14.8 
14.7 
(e) 
2,4'-diisocyanato- 5-isopropyl thio- diphenyl sulfide 
##STR11## 12.8 
12.6 
(f) 
2-(2-isocyanatoethyl- thio)-phenyl isocyanate 
##STR12## 20.3 
20.15 
(g) 
2-(6-isocyanato- hexylthio)-phenyl isocyanate 
##STR13## 16.5 
16.3 
(h) 
2-(2-isocyanato- ethylthio)-4-ethyl phenyl isocyanate 
##STR14## 17.9 
17.75 
(i) 
2-(6-isocyanato hexylthio)-4- isopropylthio-phenyl isocyanate 
##STR15## 12.45 
12.55 
__________________________________________________________________________ 
Examples 2 through 20 illustrate solutions of sulfur-containing liquid urea 
diisocyanates in isocyanate prepolymers. 
EXAMPLE 2 
85% of an isocyanate prepolymer having an isocyanate content of 3.5%, 
prepared from a linear polypropylene glycol ether having a molecular 
weight of 2,000 (OH number =56) and 2,4-tolylene diisocyanate (NCO:OH 
=2:1) is mixed at a temperature of from 60.degree. to 70.degree. C. with 
15% of the urea diisocyanate of Example 1(a). The solution of urea 
diisocyanate in the prepolymer has an isocyanate content of 5.4%. 
EXAMPLE 3 
85% of an isocyanate prepolymer containing 3.4% NCO and prepared from a 
polypropylene glycol ether having a molecular weight of 2,000 (OH number 
=56) and a commercial diisocyanatodipenyl methane mixture having an NCO 
content of 33.3% (NCO:OH =2:1) is mixed at from 60.degree. to 70.degree. 
C. with 15% of the urea diisocyanate of Example 1(b) mentioned in the 
Table. The solution has an isocyanate content of 5%. 
EXAMPLE 4 
90% of an isocyanate prepolymer having an isocyanate content of 3.5% and 
prepared from 2,4-tolylene diisocyanate and a linear polyester diol having 
a molecular weight of 2,000 (OH number =56) based on adipic acid and 
diethylene glycol is mixed at from 60.degree. to 70.degree. C. with 10% of 
the urea diisocyanate of Example 1(f) mentioned in the Table. The solution 
has an isocyanate content of 5.15%. 
EXAMPLE 5 
90% of the isocyanate prepolymer described in Example 4 is mixed at from 
60.degree. to 70.degree. C. with 10% of the liquid urea diisocyanate of 
Example 1(g) shown in the Table. The isocyanate content of the solution is 
4.8%. 
EXAMPLE 6 
85% of the isocyanate prepolymer described in Example 4 is mixed at from 
60.degree. to 70.degree. C. with 15% of the liquid urea diisocyanate of 
Example 1(i) shown in the Table. The isocyanate content of the solution is 
4.85%. 
EXAMPLE 7 
90% of the isocyanate prepolymer described in Example 2 is mixed at from 
60.degree. to 70.degree. C. with 10% of the liquid urea diisocyanate of 
Example 1(d) shown in the Table. The isocyanate content of the solution is 
4.6%. 
EXAMPLE 8 
90% of the isocyanate prepolymer described in Example 3 is mixed at from 
60.degree. to 70.degree. C. with 10% of the liquid urea diisocyanate of 
Example 1(c) shown in the Table. The isocyanate content of the solution is 
4.4%. 
EXAMPLE 9 
95% of an isocyanate prepolymer having an isocyanate content of 4.9% and 
prepared from a polyether polyol mixture of 45% of a linear polypropylene 
glycol having a molecular weight of 2,000, 5% of a trifunctional 
polypropylene glycol having a molecular weight of 4,800 and 50% of a 
linear polypropylene glycol having a molecular weight of 1,000 (OH number 
=112) and 2,4- tolylene diisocyanate (NCO/OH =2:1) is mixed with 5% of the 
liquid urea diisocyanate of Example 1(h) shown in the Table. The 
isocyanate content of the solution is 5.5%. 
EXAMPLE 10 
90% of the prepolymer described in Example 9 is mixed at from 60.degree. to 
70.degree. C. with 10% of the liquid urea diisocyanate of Example 1(e) 
shown in the Table. The isocyanate content of the solution is 5.6%. 
EXAMPLE 11 
85% of an isocyanate prepolymer having an isocyanate content of 3.3% and 
prepared from the polypropylene glycol ether diol of Example 2 and 
2,4'-diisocyanatodiphenyl sulfide (NCO/OH =2:1) is mixed at from 
60.degree. to 70.degree. C. with 15% of the liquid urea diisocyanate 
prepared according to Example 1(a). The isocyanate content of the solution 
is 5.25%. 
EXAMPLE 12 
268 g (1 mol) of 2,4'-diisocyanatodiphenyl sulfide are added to 2,348 g (1 
mol) of an isocyanate prepolymer which has an isocyanate content of 3.5% 
and has been prepared from 2,000 g of a linear polypropylene glycol ether 
having a molecular weight of 2,000 (OH number =56) and 348 g (2.0 mol) of 
2,4-diisocyanatotoluene. 9 g (0.5 mol) of water are added to this mixture 
at a temperature of from 50.degree. to 60.degree. C. within half an hour 
and the whole reaction mixture is maintained at this temperature for from 
5 to 6 hours. When evolution of CO.sub.2 has terminated (11.5 liters), a 
polyisocyanate-urea solution having a total isocyanate content of 4.7% is 
obtained. 
EXAMPLE 13 
The mixture of prepolymer and diisocyanate from Example 12 is mixed with 
18.8 g of pinacol hexahydrate and reacted at from 60.degree. to 70.degree. 
C. (corresponding to 0.5 mol of water per mol of free 
2,4'-diisocyanatodiphenyl sulfide). A polyisocyanate urea solution having 
a total isocyanate content of 4.5% is obtained after 5 to 6 hours at from 
60.degree. to 70.degree. C. 
EXAMPLE 14 
296 g (1 mol) of 2,4'-diisocyanato-3'-ethyldiphenyl sulfide are added to 
2,500 g (1 mol) of an isocyanate prepolymer having an isocyanate content 
of 3.4% which has been prepared from 2,000 g of a linear polypropylene 
glycol ether having a molecular weight of 2,000 and 500 g of a commercial 
mixture of diisocyanatodiphenyl methanes with an NCO-content of 33.3% by 
weight. 9 g (0.5 mol) of water are added to the resulting mixture within 
half an hour at from 50.degree. to 60.degree. C. and the mixture is 
stirred for from 5 to 6 hours. A polyisocyanate-urea solution having a 
total isocyanate content of 4.5% is obtained when evolution of CO.sub.2 
(11.3 liters) has terminated. 
EXAMPLE 15 
(a) 268 g (1 mol) of 2,4'-diisocyanatodiphenyl sulfide are added to 2,536 g 
(1 mol) of a prepolymer which has an isocyanate content of 3.3% and has 
been prepared from a polypropylene glycol polyether having a molecular 
weight of 2,000 and 536 g of 2,4'-diisocyanatodiphenyl sulfide. 9 g (0.5 
mol) of water are added to the mixture at from 50.degree. to 60.degree. C. 
within half an hour and the mixture is stirred for from 5 to 6 hours. When 
evolution of CO.sub.2 has terminated, a polyisocyanate urea solution 
having a total isocyanate content of 4.42% is obtained. 
(b) 200 g of the polyether diol used in (a) are prepolymerized with 804 g 
of 2,4'-diisocyanatodiphenyl sulfide and then reacted with 9 g of water 
analogously to method (a). A polyisocyanate-urea solution having a total 
isocyanate content of 4.35% is obtained. 
EXAMPLE 16 
220 g (1 mol) of 2-(2-isocyanatoethylthio)-phenyl isocyanate are added to 
2,336 g (1 mol) of a prepolymer having an isocyanate content of 3.6% 
prepared from a polyester diol having a molecular weight of 2,000 (OH 
number =56) of adipic acid and diethylene glycol and 336 g of 
1,6-hexamethylene diisocyanate. 9 g of water are added to the mixture at 
from 50.degree. to 60.degree. C. within 0.5 hours and the mixture is 
stirred for from 6 to 7 hours. The total isocyanate content of the 
solution after termination of the reaction is 4.85%. 
EXAMPLE 17 
200 g of the polyester diol used in Example 16 are prepolymerized with 105 
g of 2-(6-isocyanatohexylthio)-4-isopropylthio-phenyl isocyanate. 0.9 g of 
water are added at from 50.degree. to 60.degree. C. and the mixture is 
stirred for from 6 to 7 hours. The total isocyanate content of the 
solution after termination of the reaction is 4%. 
EXAMPLE 18 
26.8 g (0.1 mol) of 2,4'-diisocyanatodiphenyl sulfide are added to 253.6 g 
(0.1 mol) of the prepolymer from Example 15 (a). 1.1 g of water (0.61 mol) 
are slowly added dropwise at from 50.degree. to 60.degree. C. and the 
mixture is stirred for from 5 to 6 hours. The total isocyanate content is 
4.15%. 
EXAMPLE 19 
22.0 g (0.1 mol) of 2-(2-isocyanatoethylthio)-phenyl isocyanate are added 
to 255.2 g (0.1 mol) of a prepolymer having an isocyanate content of 3.2% 
obtained from a polyester diol having a molecular weight of 2,000 and an 
OH number of 56 and 55.2 g (0.2 mol) of 2- (6-isocyanatohexylthio)-phenyl 
isocyanate. 1.3 g (0.72 mol) of water are slowly added dropwise at from 
50.degree. to 60.degree. C. and the mixture is stirred for from 5 to 6 
hours. The total isocyanate content is 3.7%. 
EXAMPLE 20 
(a) 33 g (0.15 mol) of 2-(2-isocyanatoethylthio)-phenyl isocyanate are 
added to 244.0 g (0.1 mol) of a prepolymer having an isocyanate content of 
3.4% obtained from a polyester diol having a molecular weight of 2,000 and 
an OH number of 56 and 44.0 g (0.2 mol) of 
2-(2-isocyanatoethylthio)-phenyl isocyanate. 1.8 g of water (0.1 mol) are 
added dropwise at from 50.degree. to 60.degree. C. for 45 minutes and the 
mixture is stirred for from 6 to 7 hours. The total isocyanate content is 
4.5%. 
(b) 200.0 g of the polyester diol used in (a) are mixed and prepolymerized 
with 77 g of 2-(2-isocyanatoethylthio)-phenyl isocyanate. The isocyanate 
content of the prepolymer is 10.6%. 1.8 g (0.1 mol) of water are added at 
from 50.degree. to 60.degree. C. as described in (a). The total isocyanate 
content is 4.4%. 
Examples 21 through 27 illustrate the preparation of elastomers. 
EXAMPLE 21 
(a) 100 g of the polyisocyanate-urea solution having an isocyanate content 
of 5.4% prepared in Example 2 are degassed under vacuum at from 60.degree. 
to 80.degree. C. and stirred with 14.17 g of 4-chloro-3,5-diamino-benzoic 
acid-isobutylester within 30 seconds (NCO:NH.sub.2 =1.1:1). The reaction 
mixture is then poured into a metal mold which has been heated to a 
temperature of 120.degree. C. The casting time is about 5 minutes. The 
molding can be removed after about 12 minutes. 
(b) Analogous to (a) except that 10.4 g of 3,5-diethyl-2,4-diaminotoluene 
was used instead of the 4-chloro-3,5-diamino-benzoic acid-isobutylester. 
The mechanical properties of the elastomers were determined in each case 
after tempering for 24 hours at 120.degree. C. 
______________________________________ 
a b 
______________________________________ 
Tensile strength (DIN 53504) 
34.3 MPa 32.1 MPa 
Elongation at break (DIN 53504) 
644% 670% 
Tear propagation resistance 
35.7 KN/m 35 KN/m 
(DIN 53515) 
Shore hardness A (DIN 53505) 
85 83 
Elasticity (DIN 53512) 
55% 53% 
______________________________________ 
EXAMPLE 22 
100 g of the polyisocyanate-urea solution prepared in Example 4 are 
degassed under vacuum at from 80.degree. to 100.degree. C. and then 
stirred with 13.5 g of 3,5-diamino-4-chloro-benzoic acid isobutylester for 
30 seconds. The NCO/NH.sub.2 molar ratio is 1.1:1. The reaction mixture is 
poured into a mold which has been heated to 100.degree. C. After a casting 
time of 3.5 minutes and a tempering time of about 10 hours at from 
120.degree. to 130.degree. C., the molded body produced has the properties 
indicated below. 
______________________________________ 
Shore hardness A (DIN 53505) 
75.0 
Tensile strength (MPa) 20.5 
Tear propagation resistance (KN/m) 
31.9 
Elasticity (%) 48 
______________________________________ 
EXAMPLE 23 
(a) 100 g of the polyisocyanate-urea solution having an isocyanate content 
of 5.6% of Example 10 are degassed at 80.degree. C. and then stirred with 
10.8 g of 3,5-diethyl-2,4-diaminotoluene. After a casting time of 1 minute 
an elastic molded body is obtained which, when heated for a further 24 
hours at 120.degree. C., is found to have the mechanical properties set 
forth in the Table. 
(b) Analogous to (a) except that 14.4 g of 4-chloro-3,5-diamino-benzoic 
acid isobutylester is used instead of the 3,5-diethyl-2,4-diaminotoluene. 
______________________________________ 
a b 
______________________________________ 
Tensile strength (MPa) 
38.5 37.6 
Elongation at break (%) 
480 510 
Tear propagation resistance 
43.3 46.8 
(KN/m) 
Shore hardness A 88 90 
Elasticity (%) 51 52 
______________________________________ 
EXAMPLE 24 
100 g of the polyisocyanate-urea solution prepared in Example 13 are 
degassed at 80.degree. C. and stirred with 11.8 g of 
4-chloro-3,5-diamino-benzoic acid isobutylester for 30 seconds 
(NCO-NH.sub.2 =1.1:1). The reaction mixture is poured into a mold which 
has been preheated to 100.degree. C. The casting time is 5 minutes. The 
molding can be removed from the mold after 15 minutes. After a tempering 
time of 24 hours at 110.degree. C., the elastomer obtained is found to 
have the following mechanical properties: 
______________________________________ 
Tensile strength (DIN 53504) 
17.5 MPa 
Elongation at break (DIN 53504) 
638% 
Tear propagation resistance 
(DIN 53515) 24.2 KN/m 
Shore hardness A (DIN 53505) 
78 
Elasticity (DIN 53512) 50% 
______________________________________ 
EXAMPLE 25 
100 g of the polyisocyanate-urea solution prepared in Example 14 are 
reacted with 11.8 g of 4-chloro-3,5-diamino-benzoic acid isobutylester as 
described in Example 24. The casting time is 4.5 minutes and the time 
before removal from the mold is 16 minutes. The mechanical properties of 
the elastomer are as follows: 
______________________________________ 
Tensile strength (DIN 53504) 
19.7 MPa 
Elongation at break (DIN 52504) 
620% 
Tear propagation resistance 
28.2 KN/m 
(DIN 53515) 
Shore A (DIN 53505) 85 
Elasticity (DIN 53512) 51% 
______________________________________ 
EXAMPLE 26 
100 g of the polyisocyanate-urea solution having an isocyanate content of 
4.42% prepared in Example 15 (a) are mixed within 30 seconds at 
100.degree. C. with 11.6 g of 4-chloro-3,5-diamino-benzoic acid 
isobutylester (NCO:NH.sub.2 =1.1:1) and the mixture is poured into a mold 
which has been preheated to 110.degree. C. The mixture remains in a 
pourable state for 4 minutes. The casting can be removed from the mold 
after 13 minutes. The following mechanical properties are obtained after a 
tempering time of 24 hours at 110.degree. C. 
______________________________________ 
Tensile strength (DIN 53504) 
19.3 MPa 
Elongation at break (DIN 53504) 
625% 
Tear propagation resistance 
28.5 KN/m 
(DIN 53515) 
Shore A (DIN 53505) 77 
Elasticity (DIN 53512) 49% 
______________________________________ 
EXAMPLE 27 
100 g of the polyisocyanate-urea solutions prepared in Examples 20 (a) and 
20 (b) and having isocyanate contents of 4.5 and 4.4%, respectively, are 
reacted at 100.degree. C. with 11.8 g and 11.55 g, respectively, of 
4-chloro-3,5-diamino-benzoic acid isobutylester as described in Example 
26. (NCO/NH.sub.2 =1.1:1). The casting time is 6 minutes and the time 
until removal from the mold is 16 minutes. The mechanical properties of 
the two elastomers are as follows: 
______________________________________ 
Solution 20 a 
Solution 20 b 
______________________________________ 
Tensile strength 14.7 MPa 14.8 MPa 
(DIN 53504) 
Elongation at break 
825% 850% 
(DIN 53504) 
Tear propagation 21.4 KN/m 22.4 KN/m 
resistance (DIN 53515) 
Shore A (DIN 53505) 
72 73 
Elasticity (DIN 53512) 
52% 50% 
______________________________________