Polyurea dispersions in organic isocyanates

A dispersion of a polyurea in an aromatic polyisocyanate is prepared by mixing the polyisocyanate with one or more aliphatic diprimary diamines having (a) at least one amine group attached to a carbon atom having not more than one hydrogen atom attached thereto or (b) at least one amine group attached to a carbon atom which is itself attached to a carbon atom having not more than one hydrogen atom attached thereto, provided that both amine groups are not attached directly to separate rings of an alkylene-linked polycyclic aliphatic ring system. The reaction preferably takes place at a temperature in the range 20.degree. C. to 60.degree. C. The polyurea dispersion products are useful for manufacture of polyurethane foams and elastomers of superior physical properties.

This invention relates to organic isocyanates and in particular to 
dispersions of polyureas in organic isocyanates. 
The production of materials such as polyurethanes foams and elastomers from 
organic isocyanates is well known. The physical properties of such 
materials may be improved if a finely divided particulate material is 
dispersed throughout the body of the foam or elastomer. 
Several methods have been proposed for the introduction of organic or 
inorganic filters into polyurethane foams with a view to providing 
improved properties such as greater hardness. 
In U.K. Pat. No. 1,501,172 there is described a process for the production 
of a polyurethane foam which comprises reacting a polyisocyanate with a 
dispersion of a polyurea (and/or at least one polyhydrazicarbonamide) in a 
compound containing at least two hydroxyl groups and having a molecular 
weight of from 200 to 1600 (for example a high molecular weight polyether) 
in the presence of a blowing agent. The polyurea dispersion is formed by 
the reaction of a polyamine with an isocyanate in the presence of the high 
molecular weight polyether dispersant medium. A number of polyamines are 
disclosed as being suitable for the reaction of which the simplest is 
ethylene diamine. The presence of the high molecular weight polyether 
dispersant medium is essential to modify the reaction of the polyamine 
with the isocyanate. 
The problem of the vigour of the reaction of conventional diamines such as 
ethylene diamine with isocyanates is discussed in U.S. Pat. No. 4,320,067 
where it is noted that when a commercial polyisocyanate such as tolylene 
diisocyanate-isomeric mixture is mixed with commercial ethylene diamine, 
the "expected vigorous, almost uncontrollable reaction takes place". The 
patent suggests the formation of modified polyisocyanates by the reaction 
of the isocyanate with (a) a polyamine containing more than three 
non-aromatically bound, basic nitrogen atoms, of which at least two are 
primary and/or secondary amino nitrogen atoms or (b) a polyamine mixture 
which contains an average of more than three non-aromatically bound, basic 
nitrogen atoms, of which at least two are primary and/or secondary amino 
nitrogen atoms. 
In U.S. Pat. No. 4,264,519 there is once more considerable discussion of 
the problems encountered as a result of the high reactivity of organic 
polyisocyanates with conventional low molecular weight organic polyamines 
in the production of solutions or dispersions of ureas and biurets. In 
this patent, the problem is solved by the use of a special reaction vessel 
into which the reactants are injected under pressure and in a carefully 
defined manner. 
In U.S. Pat. No. 3,943,158 there are disclosed stable homogeneous solutions 
of urea diisocyanates formed by the reaction of organic diisocyanates with 
secondary diamines of defined formula. 
We have now found that, surprisingly, stable polyrea dispersions may be 
obtained without the need for complex mixing vessels or techniques by the 
reaction of certain defined primary diamines with aromatic isocyanates. 
According to the present invention there is provided a process for the 
manufacture of a dispersion in an aromatic polyisocyanate of a polyurea 
which comprises reacting by simple mixing the polyisocyanate with one or 
more aliphatic diprimary diamines having (a) at least one amine group 
attached to a carbon atom having not more than one hydrogen atom attached 
thereto or (b) at least one amino group attached to a carbon atom which is 
itself attached to a carbon atom having not more than one hydrogen atom 
attached thereto, provided that both amine groups are not attached 
directly to separate rings of an alkylene-linked polycyclic aliphatic ring 
system. 
Thus for example there is excluded from the present invention by the above 
proviso diamino-dicyclohexylmethane and derivatives thereof wherein the 
two amine groups are respectively attached directly to the separate 
cyclohexyl rings 
The term "simple mixing" as used herein means mixing in a conventional 
mixing vessel using conventional mixing means such as stirring with a 
conventional stirrer or high-shear stirrer such as a SILVERSON (trade 
mark) stirrer. 
Preferably the aliphatic diprimary diamine has both amine groups attached 
either to a carbon atom having not more than one hydrogen atoms attached 
thereto or to a carbon atom which is itself attached to a carbon atom 
having not more than one hydrogen atom attached thereto, provided that 
both amine groups are not attached directly to separate rings of an 
aliphatic ring system. Thus we have found for example that 
trimethylhexamethylene diamine (1,6-diamino-2,2,4-trimethylhexane)--in 
which only one of the two amine groups is attached to a carbon atom which 
is itself attached to a carbon atom having no hydrogen atoms attached 
thereto--gives satisfactory polyurea dispersions when mixed with tolylene 
diisocyanate, but has a tendency to form inferior dispersions with a 
degree of gelling when using isocyanates based on diphenylmethane 
diisocyanates. 
Especially preferred diamines are diamine derivatives of aliphatic cyclic 
ring systems, for example six membered ring systems and derivatives 
thereof, or fused polycyclic ring systems, for example the tricyclodecane 
fused ring system and derivatives thereof. Examples of especially 
preferred diamines are isophorone diamine 
(3-aminomethyl-3,5,5-trimethylcyclohexylamine), and p-methane diamine 
(1-methyl-4-(2-methyl-2-aminoethyl)cyclohexylamine). 
Mixtures of two or more diamines may be used if desired 
The aromatic polyisocyanate may be any of the aromatic isocyanates known in 
the art to be useful for the formation of polyurethane derivatives such as 
polyurethane foams and elatomers. The term "polyisocyanate" as used herein 
includes a diisocyanate. Of particular interest are for example tolylene 
diisocyanate and especially diphenylmethane diisocyanates (MDI) which are 
commercially available in a variety of forms. Suitable diphenylmethane 
isocyanates include 
(a) diphenylmethane-4,4'-diisocyanate and mixtures thereof with other 
isomers of diphenylmethane diisocyanate; 
(b) methylene bridged polyphenylpolyisocyanates prepared by phosgenation of 
mixtures of polyamines obtained by the condensation of aniline and 
formaldehyde and known in the art as "crude" or "polymeric" MDI; 
(c) isocyanate ended polymers and oligomers obtained by reacting 
diphenylmethane diisocyanates or "crude MDI" with a monomeric glycol or 
polyol (or mixtures thereof) or with a hydroxyl-ended polyester or 
polyether and known in the art as "MDI prepolymers"; and 
(d) modified diphenylmethane diisocyanates or "modified crude MDI" which 
are compositions in which a proportion of the isocyanate groups are 
converted into other functional groups such as carbodiimide, uretonimine 
or allophanate groups, or in which a proportion of the isocyanate groups 
are reacted with an isocyanate-reactive compound. 
Mixtures of MDI variants may also be used if desired. 
The polyurea dispersion may be formed by adding the diamine to the organic 
isocyanate over a period of time whilst stirring the mixture. As discussed 
above, there is no need to employ complex mixing techniques or apparatus 
such as that described in U.S. Pat. No. 4,264,519. The reaction 
conveniently takes place at ambient temperature, although higher or lower 
temperatures may be used if desired. The temperature should not be 
sufficiently high to convert the dispersed polyurea particles into the 
corresponding biuret, and it is preferred that the temperature remains 
below 90.degree. C. Temperatures in the range of 20.degree. C. to 
60.degree. C. are preferred. 
Preferably the diamine is a liquid and is added to the organic isocyanate 
in that form. If a solid diamine is used, it may be added in the form of a 
solution in a suitable solvent. 
If the polyurea is to be formed from a modified diphenylmethane isocyanate, 
the diamine may if desired be added during the formation of the modified 
MDI. Thus if a modified MDI is to be formed by the reaction of a 
diphenylmethane diisocyanate with for example a mixture of monomeric 
glycols, the diamine may be added before or after the reaction of the 
diphenylmethane diisocyanate with the glycols, or the diamine may be added 
at an intermediate stage after the reaction of the diphenylmethane 
diisocyanate with a portion of the glycols, the remainder of the glycols 
being added after the diamine. 
We have found that the present invention provides stable, mobile 
dispersions which are suitable for preparing polyurethane products of 
superior physical properties. The expression "stable" dispersion as used 
herein is not to be taken to imply that the dispersion obtained is 
indefinitely stable under all conditions. It is sufficient if the 
dispersion remains workable for a reasonable period of time having regard 
for its use in the preparation of polyurethane products. Equally, the 
settling of a minor proportion of the dispersed phase is not necessarily 
deleterious, provided that a good dispersion may be reformed on gentle 
stirring. 
The term "polyurea" as used herein includes a diurea formed by the reaction 
of the diamine with two molecules aromatic isocyanate, one isocyanate 
group in the aromatic isocyanate reacting with each amine group. Thus, for 
example one mole of diamine reacts with two molecules of an aromatic 
diisocyanate to form the diurea. Whilst the scope of the present invention 
is not to be taken to be limited by any particular theory, it is believed 
that amajor proportion of the "polyurea" may be a diurea with a minor 
proportion being higher polyaddition products. For convenience, the 
"calculated polyurea content" of the dispersion, as that expression is 
used herein, is calculated on the basis of the reaction of one molecule of 
diamine with two molecules of aromatic isocyanate. The calculated polyurea 
content of the dispersion may be up to 50 percent by weight of the total 
isocyanate composition, but is preferably not greater than 25 percent by 
weight of the total isocyanate composition, for example from 3 to 25 
percent by weight of the total isocyanate composition. 
The present invention includes the manufacture of polyurethane products, 
for example polyurethane foams and elastomers, in known manner from the 
dispersion of a urea in an organic polyisocyanate described above, and 
also includes polyurethane products so prepared. 
Polyurethane products are made by reacting a polyisocyanate with a polyol. 
The urea/polyisocyanate dispersions of the present invention may be used 
in the same manner as conventional polyisocyanates. The nature of the 
polyurethane product, for example the polyurethane foam may be varied 
depending on the exact isocyanate and a variety of other factors as is 
conventional in the art. 
Other conventional ingredients may be used in making the polyurethanes. 
These include catalysts, for example tertiary amines and organic tin 
compounds, surfactants, cross linking or chain lengthening agents, for 
example, low molecular weight diols, triols and diamines, flame proofing 
agents, for example, halogenated alkyl phosphates, fillers and pigments. 
Blowing agents used for forming polyurethane foams include water, which 
reacts with the polyisocyanate to form carbon dioxide, and inert low 
boiling liquids such as halogenated hydrocarbons. 
If desired, the dispersion of the polyurea in the aromatic isocyanate 
according to the present invention may be used in conjunction with a 
polyol which itself contains a particulate dispersion, for example a 
polyol dispersion such as that described in U.K. Pat. No. 1,501,172. 
The invention is illustrated by the following Examples in which all parts 
and percentages are by weight unless otherwise stated.

EXAMPLE 1 
Isophoronediamine (16 g) was added dropwise with rapid stirring at room 
temperature over a period of half an hour to 400 g of a liquid 
uretonimine-modified 4,4'-diphenylmethane diisocyanate having an 
isocyanate value of 29.2%. The mixture was stirred for a further hour at 
room temperature after the amine addition was complete, and a stable white 
mobile dispersion was obtained. The dispersion had an isocyanate value of 
25.3% (calculated 25.9%). The infrared spectrum showed strong bands 
characteristic of a polyurea based on 4,4'-diphenylmethane diisocyanate. 
The calculated polyurea content of the dispersion was 15.1%. 
EXAMPLE 2 
p-Menthanediamine (10 g) was added dropwise with rapid stirring at room 
temperature over a period of half an hour to 200 g of a mixed glycol 
prepolymer/uretonimine-modified 4,4'-diphenylmethane diisocyanate of 
isocyanate value 26.0%. The mixture was stirred for a further half hour at 
room temperature to form a stable, creamy white mobile dispersion having 
an isocyanate value of 22.03% (calculated 22.1%). The infrared spectrum 
showed strong bands characteristic of a polyurea based on 
4,4'-diphenylmethane diisocyanate. 
The calculated polyurea content of the dispersion was 18.7%. 
EXAMPLE 3 
3(4),8(9)-Bis(aminomethyl)tricyclodecane (20 g) was added dropwise with 
rapid stirrung at room temperature over a period of 15 minutes to 200 g of 
a liquid uretonimine modified 4,4'-diphenylmethanediisocyanate having an 
isocyanate value of 29.2%. The mixture was stirred for a further 30 
minutes at room temperature after the amine addition was complete and a 
stable, mobile, white dispersion was obtained. The dispersion had an 
isocyanate value of 21.8% (calculated 22.4%). 
The calculated polyurea content of the dispersion was 32.5%. 
EXAMPLE 4 
2,2,4,4-tetramethyl-1,3-diaminocyclobutane (5 g) was added dropwise at room 
temperature with rapid stirring to 100 g of a liquid uretonimine-modified 
4,4'-diphenylmethanediisocyanate having an isocyanate value of 29.2%. The 
addition took place over the period of 15 minutes. The mixture was then 
stirred for a further 30 minutes at room temperature, and a stable, 
mobile, white dispersion was obtained which had an isocyanate value of 
24.0% (calculated 23.4%) and a calculated polyurea content of 21.5%. 
EXAMPLE 5 
1,4-Di(aminomethyl)cyclohexane (2.5 g) was added dropwise at room 
temperature with rapid stirring to 100 g of a liquid uretonimine-modified 
4,4'-diphenylmethanediisocyanate having an isocyanate value of 29.2%. The 
addition took place over the period of 10 minutes. The mixture was then 
stirred for a further 30 minutes at room temperature, and a stable, 
mobile, white dispersion was obtained which had an isocyanate value of 
27.1% (calculated 26.4%) and a calculated polyurea content of 5.5%. 
EXAMPLE 6 
Isophorone diamine (3.28 g) was added dropwise at room temperature with 
rapid stirring to 100 g of tolylene diisocyanate having an isomer ratio of 
2,4' to 2,6' isomer of 80:20. The addition took place over a period of 10 
minutes, and the mixture was then stirred for a further half hour at room 
temperature. A stable mobile white dispersion was obtained which had an 
isocyanate value of 44.4% (after storage for one day) and a calculated 
poly urea content of 10%. 
EXAMPLE 7 
The process of Example 6 was repeated except that 6.56 g of isophorone 
diamine was used to give an stable dispersion having an isocyanate value 
of 40.2% and a calculated urea content of 20%. 
EXAMPLE 8 
The process of Example 6 was repeated except that instead of isophorone 
diamine there was used 3.12 g of trimethylhexamethylene diamine. The 
product was a stable mobile white dispersion having an isocyanate value of 
44.1% and a calculated urea content of 10%. 
EXAMPLE 9 
A polyurea dispersion was prepared using a liquid diphenylmethane 
diisocyanate composition in which a proportion of the isocyanate groups 
are reacted with a mixture of three alkylene glycols as described in U.K. 
Pat. No. 1596469. The liquid diphenylmethane diisocyanate composition 
described in this patent is especially useful for the manufacture of 
micro-cellular elastomers as used for example in shoe soles. 
A comparison was made between a micro-cellular shoe soling elastomer 
prepared using a liquid diphenylmethane diisocyanate composition 
containing a polyurea dispersion according to the present invention and an 
exactly corresponding liquid diphenyl methane diisocyanate composition 
containing no polyurea dispersion. To ensure that the two compositions 
were truly comparable, the polyurea dispersion was made such that a 
proportion of the glycol mixture was replaced by the diamine so that the 
resultant composition had the same isocyanate value as the liquid 
diphenylmethane composition containing no polyurea dispersion. 
Manufacture of Polyurea Dispersion 
The diamine was added at an intermediate stage in the modification of 
4,4'-diphenylmethane diisocyanate (4,4'-MDI) by reaction with a mixture of 
three glycols as described in U.K. Pat. No. 1596569. 
Thus 250 g (1.99 moles) of the glycols was added dropwise with rapid 
stirring over a period of 30 minutes to 4987 g (19.93 moles) of pure 
4,4'-MDI held at 60.degree. C. The mixture was stirred for a further 30 
minutes at 60.degree. C., and then 286 g (1.68 moles) of isophorone 
diamine was added dropwise over a period of 75 minutes. The mixture was 
stirred for a further 30 minutes, and then 49 g (0.39 moles) of glycol 
mixture was added over a period of 5 minutes and the reaction mixture 
maintained at 60.degree. C. for a further 100 minutes. 
The resulting stable dispersion had an isocyanate value of 23.3% and a 
viscosity of 420 cp at 25.degree. C. The calculated polyurea content was 
19.8%. A slight settling of the dispersed phase was observed after 24 
hours, but the stable dispersion was readily reformed on gentle stirring. 
EXAMPLE 10 
Manufacture of the Shoe Soling Material 
The polyurea dispersion of Example 9 was used to prepare an elastomer of 
the type used in shoe soling. A comparison was made with a corresponding 
glycol modified pure 4,4'-MDI not containing the polyurea dispersion but 
having a corresponding NCO value (23.0%). The microcellular elastomer was 
made in conventional manner using the following foaming mixture: 
______________________________________ 
Polyether polyol of hydroxyl value 35 mg KOH/g 
84 parts 
Chain extender 9 parts 
DABCO 0.4 parts 
Tin catalyst 0.02 parts 
water 0.2 parts 
fluorocarbon blowing agent 6.0 parts 
Glycol modified 4,4'-MDI (Example 9/comparison) 
48 parts 
______________________________________ 
The properties of the elastomer obtained using the polyurea dispersion of 
Example 9 and the comparison containing no polyurea dispersion 
respectively are given below: 
______________________________________ 
Modified MDI 
Elastomer Property 
of Ex. 9 Comparison 
______________________________________ 
Density (Kg/m.sup.3) 
625 615 
Shore A hardness 
79 65 
Tensile strength (MN/m.sup.2) 
5.1 4.6 
Elongation (%) 320 355 
Tear strength (KN/m) 
15.9 12.9 
______________________________________ 
The comparison demonstrates the increased elastomer hardness obtained using 
the polyurea dispersion according to the present invention. 
EXAMPLE 11 
231.9 g (1.36 moles) of isophorone diamine was added dropwise with rapid 
stirring to 5172.7 g (17.00 moles) of a liquid uretonimine modified 
4,4'-diphenylmethane diisocyanate (4,4'-MDI) having an NCO value of 29.2%. 
The addition took place over a period of 65 minutes, and the temperature 
was maintained at 20.degree. C. The mixture was stirred for a further 240 
minutes at a temperature of 20.degree. C. 
The resulting stable mobile white dispersion had a viscosity of 460 cp at 
25.degree. C. and an NCO value of 25.85%. The calculated polyurea content 
was 19.65%. 
Some settling of the dispersed phase was observed after 72 hours, but a 
stable dispersion was readily re-formed on gentle stirring. 
EXAMPLE 12 
The polyurea dispersion of Example 11 was used to prepare an elastomer of 
the type used in automotive applications such as bumpers. A comparison 
elastomer was also prepared using a corresponding 4,4'-MDI composition 
which contained no polyurea dispersion. To ensure that the MDI samples 
with and without the polyurea dispersion were strictly comparable, there 
was used for the comparison a mixed glycol/uretonimine modified 4,4'-MDI 
having the same NCO value as the uretonimine modified 4,4'-MDI containing 
the polyurea dispersion. 
A conventional foaming mixture was used as follows: 
______________________________________ 
Polyether polyol of hydroxyl value 
80 parts 
35 mg KOH/g 
Chain extender 20 parts 
DABCO 0.4 parts 
Tin catalyst 0.01 parts 
MDI/Polyurea dispersion of Example 11 
59 parts 
(or comparison MDI compositon) 
______________________________________ 
The properties of the resultant elastomers were as follows: 
______________________________________ 
Polyurea 
Dispersion 
Property of Ex. 11 Comparison 
______________________________________ 
Density (kg/m.sup.3) 
900 950 
Hardness (Shore D) 
63 59 
Tensile strength (MN/m.sup.2) 
20.5 20.6 
Elongation at break (%) 
120 140 
Flexural Modulus (MPa) 
430 340 
______________________________________ 
The results show the increased hardness and stiffness obtained when using 
the polyurea dispersion according to the present invention. 
EXAMPLE 13 
Isophorone diamine (187.8 g-1.10 moles) was added dropwise with rapid 
stirring to 4822.7 g (13.00 moles) of polymeric (crude) MDI-diisocyanate 
diphenylmethane containing higher functionality polyisocyanates. The 
addition took place over a period of 55 minutes during which time the 
temperature rose from the initial 22.degree. C. to 29.degree. C. The 
mixture was then stirred for another 65 minutes at 25.degree. C. 
The resulting thixotropic dispersion had a viscosity of 2797 cp at 
25.degree. C. and an NCO value of 27.34%. The calculated polyurea content 
was 20.11%. No settling of the dipsersed phase was detected after standing 
for a week. 
EXAMPLE 14 
3(4),8(9)-Bis(aminomethyl)tricyclodecane (140.1 g-0.72 moles) was added 
dropwise with rapid stirring to 2503 g (10.00 moles) of Diphenyl methane 
diisocyanate (mainly 4,4' isomer with a small percentate of the 2,4' 
isomer). The addition took place over a period of 95 minutes and the 
temperaure was held at 45.degree. C. The mixture was then stirred for a 
further 80 minutes. 
Polyether glycol (1000.8 g-0.50 moles) was added dropwise to the reaction 
mixture over a period of 30 minutes at a temperature of 55.degree. C. and 
the mixture was maintained at 80.degree. C. for a further 120 minutes. The 
mixture was cooled to 50.degree. C. and blended with 1298.8 g (3.50 moles) 
of polymeric (crude) MDI and the mixture was stirred for a further 30 
minutes. 
The resulting stable dispersion had an isocyanate value of 21.87% and a 
viscosity of 538 cP at 25.degree. C. The calculated polyurea content was 
10.14%. 
There was no evidence of any settling of the dispersed phase after the 
dispersion had been standing for a week. 
EXAMPLE 15 
The polyurea dispersion of Example 14 was used to prepare a flexible foam 
moulding using a conventional formulation and was compared with a 
corresponding isocyanate which di not contain the polyurea dispersion. 
The comparison isocyanate was prepared in exactly the same manner as that 
of Example 14 and used the same quantities of reactants except that no 
tricyclo-decane diamine was added. No attempt was made to compensate for 
the isocyanate value which would have reacted with the diamine and in 
consequence the isocyanate value of the resultant composition was higher 
(24.3%) than that of the polyurea dispersion of Example 14. In this 
instance therefore, the proportion of the comparison isocyanate used in 
the form formulation was reduced proportionately so that strictly 
comparable foams were produced. 
The foam formulation used was as follows: 
______________________________________ 
Example 9 
Comparison 
______________________________________ 
Polyether polyol of 
84.55 parts 
84.55 parts 
hydroxyl value 35 mg KOH/g 
Water 2.8 parts 2.8 parts 
Amine catalyst system 
1.56 parts 
1.56 parts 
(based on DABCO) 
Silicone surfactant 
0.93 parts 
0.93 parts 
Fluorocarbon blowing agent 
10.2 parts 
10.2 parts 
Polyurea dispersion of Example 9 
71.6 parts 
65.0 parts 
(or comparison isocyanate) 
______________________________________ 
Flexible foam mouldings having the following properties were obtained: 
______________________________________ 
Property Example 9 Comparison 
______________________________________ 
Density (Kg/m.sup.3) 51.3 51.6 
Indentation hardness (Kg) 
25% 26 22.5 
40% 37 30 
50% 48 38 
65% 83 59 
______________________________________ 
The comparison shows the improved foam hardness obtained using the polyurea 
dispersion according to the present invention. 
COMISON A 
The procedure of Example 1 was repeated using ethylene diamine in place of 
the isophorone diamine. There was a vigorous reaction with the formation 
of a flocculant precipitate. No stable dispersion was obtained. 
COMISON B 
The procedure of Example 1 was repeated using hexamethylene diamine in 
place of the isophorone diamine. There was a vigorous reaction with the 
formation of a flocculant precipitate. No stable dispersion was obtained.