Process for the production of isocyanurate polyisocyanates, the compounds obtained by this process and their use

The present invention is directed to a process for the production of isocyanurate polyisocyanates by the partial trimerization of the isocyanate groups of aliphatic diisocyanates in the presence of catalysts which accelerate the trimerization of isocyanate groups, termination of the trimerization reaction at the particular degree of trimerization required and removal of unreacted starting diisocyanate and, optionally, other volatile constituents, characterized in that at least one diol containing ester groups and having an average molecular weight of 350 to 950 is added to the reaction mixture at any time before removal of the excess starting diisocyanate in a quantity of 1 to 50% by weight, based on the weight of the diisocyanate used as starting material, the type of reactants and the quantitative ratios between them being selected so that, on completion of the reaction, at least 10% by weight free starting diisocyanate is still present in the reaction mixture, not including any inert solvent used, and the molar ratio of isocyanurate groups to urethane groups in the end products is about 20:1 to 0.2:1. The present invention is also directed to the isocyanurate polyisocyanates obtained by this process and the use of these isocyanurate polyisocyanates, optionally blocked by blocking agents for isocyanate groups, for the production of polyurethane plastics, particularly two-component polyurethane lacquers.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a new process for the production of isocyanurate 
polyisocyanates (polyisocyanates containing isocyanurate groups) 
containing urethane and ester groups, to the compounds obtained by this 
process and to their use as the polyisocyanate component for the 
production of polyurethane plastics, in particular two-component 
polyurethane lacquers (coatings). 
2. Description of the Prior Art 
The production of isocyanurate polyisocyanates is known (cf. for example 
GB-P 920,080, DE-AS 1,667,309, DE-OS 3,100,262, DE-OS 3,219,608, DE-OS 
3,240,613, EP-A-10,589, EP-A-57,653, EP-A-89,297 or EP-A-187,105). Some of 
these prior publications also mention the use of subequivalent quantities 
of compounds containing hydroxyl groups. Thus, DE-AS 1,667,309 for example 
describes the production of isocyanurate polyisocyanates using compounds 
containing hydroxyl groups as co-catalysts. DE-OS 3,219,608 describes a 
use of polyhydric alcohols having a molecular weight below 3000 in a 
quantity of up to 15 mole-%, based on HDI used, in the production of 
isocyanurate polyisocyanates based on this starting diisocyanate. Suitable 
polyhydric alcohols according to this prior publication also include 
unspecified polyester polyols. In the process according to EP-A-155,559, 
low molecular weight diols containing lateral alkyl groups are used as 
modifying agents. 
In all the known prior-published processes, the object of the urethane 
modification is merely to provide a suitable solvent for the catalyst, to 
achieve suitable co-catalysis or to establish compatibility with various 
polyols. None of the prior publications cited above discloses how it is 
possible to modify isocyanurate polyisocyanates in such a way that they 
are optimally suitable for the production of highly elastic lacquers which 
retain their elasticity, even at low temperatures of down to -40.degree. 
C. 
Aliphatic isocyanurate polyisocyanates, particularly those based on 
1,6-diisocyantohexane (hereinafter referred to as "HDI"), have acquired 
industrial significance. They are primarily used as the polyisocyanate 
component in two-component polyurethane lacquers, but may also be used for 
the production of moisture-hardening one-component polyurethane binders 
or, when blocked by blocking agents for isocyanate groups, in 
heat-crosslinkable polyurethane lacquers. These lacquers are used mainly 
for lacquering non-flexible substrates, such as metal and wood, and are 
distinguished by high light stability and weather resistance, extreme 
hardness and very good adhesion. HDI-based isocyanurate polyisocyanates 
are particularly distinguished from corresponding biuret polyisocyanates, 
which are also used on an industrial scale, by greatly improved resistance 
to yellowing and chemicals, for example by their resistance to tar stains. 
The chemical bases for the various polyurethane lacquers are described 
inter alia in "Lackkunstharze" by Hans Wagner and Hans Friedrich Sarx, 
Carl Hanser Verlag, Munchen 1971, pages 153 to 173 and in "Lehrbuch der 
Lacke and Beschichtungen" Vol. 1, Part 2, by Hans Knittel, Verlag W. A. 
Colomb, Berlin-Oberschwandorf 1973, pages 512 to 612. 
However, state-of-the-art polyurethane lacquers, particularly two-component 
polyurethane lacquers, often lead to highly crosslinked lacquer coatings 
wherein the elasticity often fails to satisfy the requirements of coatings 
for flexible substrates. Flexible plastic components are being used to an 
increasing extent, particularly in the automotive field, in efforts to 
improve safety. These flexible moldings (fenders, spoilers, wing mirror 
housings and the like) are relatively large and, accordingly, largely 
determine the external appearance of the vehicle. For this reason, 
moldings of the type in question have to be lacquered. In addition, the 
surfaces of the plastics are degraded by the effects of weather and hence 
have to be protected accordingly. 
However, elastic lacquer films are also required for non-elastic plastic 
moldings to prevent mechanical damage to such moldings. For example, hard, 
but tough thermoplasts have to be lacquered with highly elastic, extremely 
resistant lacquers to prevent the lacquer film from cracking in the event 
of mechanical damage or under the effect of other external influences and 
the cracks from propagating in the compact plastic. Accordingly, the 
lacquer finish, above all the surface lacquer, applied to such moldings 
has to satisfy demands far exceeding those of a normal lacquer finish. 
These problems were partially solved by the development of hydroxyl 
polyesters and polyacrylates which, by virtue of their structure, can be 
processed to elastic lacquer films. However, it was not possible in this 
way to eliminate all existing difficulties. The lacquer films formed are 
often not sufficiently hard and are not sufficiently crosslinked and/or 
resistant to chemicals. 
In addition, the diisocyanate-based, for example HDI-based, isocyanurate 
polyisocyanates available for the crosslinking of these polyhydroxyl 
compounds are often incompatible with the polyhydroxyl compounds or lead 
to clouding on dilution with various solvents. 
These disadvantages have prevented known HDI-based isocyanurate 
polyisocyanates from acquiring any real significance in the lacquering of 
plastics despite their outstanding technical properties. 
Accordingly, an object of the present invention is to provide new 
isocyanurate polyisocyanates which 1) in combination with state-of-the-art 
polyhydroxyl compounds provide two-component polyurethane lacquers which 
satisfy the particular requirements mentioned above 2) in particular, are 
optimally suited to the lacquering of elastic plastic moldings and 3) may 
also be used with advantage for the production of moisture-hardening 
one-component binders or, in blocked form, for the production of 
heat-crosslinkable lacquer binders. 
This object may be achieved by isocyanurate polyisocyanates according to 
the invention which are described in detail in the following. 
SUMMARY OF THE INVENTION 
The present invention is directed to a process for the production of 
isocyanurate polyisocyanates by the partial trimerization of the 
isocyanate groups of aliphatic diisocyanates in the presence of catalysts 
which accelerate the trimerization of isocyanate groups, termination of 
the trimerization reaction at the particular degree of trimerization 
required and removal of unreacted starting diisocyanate and, optionally, 
other volatile constituents, characterized in that at least one diol 
containing ester groups and having an average molecular weight of 350 to 
950 is added to the reaction mixture at any time before removal of the 
excess starting diisocyanate in a quantity of 1 to 50% by weight, based on 
the weight of the diisocyanate used as starting material, optionally using 
diols free from ester groups and having a molecular weight in the range 
from 62 to 300, the molar ratio of diols free from ester groups to diols 
containing ester groups being up to 1:1, and reacted with isocyanate 
groups to form urethane groups, the type of reactants and the quantitative 
ratios between them being selected so that, on completion of the reaction, 
at least 10 % by weight free starting diisocyanate is still present in the 
reaction mixture, not including any inert solvent used, and the molar 
ratio of isocyanurate groups to urethane groups in the end products is 
about 20:1 to 0.2:1. 
The present invention is also directed to the isocyanurate polyisocyanates 
obtained by this process and the use of these isocyanurate 
polyisocyanates, optionally blocked by blocking agents for isocyanate 
groups, for the production of polyurethane plastics, particularly 
two-component polyurethane lacquers.

DETAILED DESCRIPTION OF THE INVENTION 
Starting materials for the process according to the invention include (i) 
aliphatic diisocyanates and (ii) selected polyester diols. 
The aliphatic diisocyanates used as starting diisocyanate (i) are organic 
diisocyanates containing aliphatically and/or cycloaliphatically bound 
isocyanate groups. Typical examples include 1,6-diisocyanatohexane (HDI), 
1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl cyclohexane (IPDI) or 
4,4'-diisocyanatodicyclohexylmethane. (Cyclo)aliphatic diisocyanates other 
than HDI are preferably mixed with HDI. This means that the starting 
diisocyanate preferably used in accordance with the invention is either 
HDI or a mixture of HDI with other (cyclo)aliphatic diisocyanates of the 
type mentioned by way of example. The mixture preferably contains at least 
30 mole-%, more preferably at least 70 mole-% HDI. Most preferably HDI is 
used as sole starting diisocyanate. 
The diisocyanates used in accordance with the invention as starting 
materials may be used in technically pure form. In a particularly 
preferred embodiment, however, HDI substantially free from carbon dioxide 
is used as sole starting diisocyanate because a particularly mild 
trimerization reaction can be obtained in this way using minimal 
quantities of catalysts. 
The HDI used with particular preference as the starting diisocyanate has a 
carbon dioxide content of less than 20 ppm (weight), preferably less than 
10 ppm (weight) and more preferably less than 5 ppm (weight). Technical 
HDI purified by distillation, of the type previously used for the 
production of isocyanurate polyisocyanates, contains considerable 
quantities (approximately 20 ppm to 100 ppm (weight)) of carbon dioxide. 
Carbon dioxide can enter the HDI during the production process, for example 
in the phosgenation of carbonic acid salts of hexamethylenediamine. It can 
also be taken up from the air during storage and can be formed by chemical 
reaction of the NCO groups with each other, for example by 
carbodiimidization, or by reaction with moisture. HDI freshly purified by 
vacuum distillation contains, for example, 40 ppm carbon dioxide after 24 
hours in a sealed container. HDI stored over a period of about 6 months 
can contain up to 0.6% by weight carbon dioxide when the container has 
been opened during the period of storage. 
Carbon dioxide can be removed from HDI by blowing out with ultra-pure 
nitrogen or with a noble gas, such as argon, for example at 0.degree. to 
70.degree. C. Although higher temperatures may be applied, they do not 
afford any clear advantages. 
It is of course also possible in a preferred variant to initially modify 
HDI containing more than 20 ppm carbon dioxide with a subequivalent 
quantity of ester diol in accordance with the invention, subsequently 
remove most of the dissolved carbon dioxide and, finally, carry out the 
trimerization reaction. 
The polyester diols (ii) to be used in the process according to the 
invention have an average molecular weight (calculated from the hydroxyl 
number) of 350 to 950, preferably of 500 to 800. Suitable polyester diols 
include known polyester diols synthesized from diols and dicarboxylic 
acids. Suitable diols for the production of the polyester diols include 
dimethylol cyclohexane, ethanediol, propane-1,2- and -1,3-diol, 
butane-1,2-, -1,3- and -1,4-diol and neopentyl glycol. Mixtures thereof 
with hexane-1,6-diol are preferred. In a particularly preferred 
embodiment, hexane-1,6-diol is the sole diol component. Suitable 
dicarboxylic acids include aromatic dicarboxylic acids such as phthalic 
acid, isophthalic acid and terephthalic acid; cycloaliphatic dicarboxylic 
acids such as hexahydrophthalic acid, tetrahydrophthalic acid, 
endomethylene tetrahydrophthalic acid and anhydrides thereof; and 
preferably aliphatic dicarboxylic acids such as succinic acid, glutaric 
acid, adipic acid, suberic acid, azelaic acid and sebacic acid or 
anhydrides thereof. 
Mixtures of the starting materials mentioned by way of example for the 
production of the polyesters may also be used. It is also possible to use 
mixtures of different polyesters of the type mentioned in the process 
according to the invention. 
It is particularly preferred to use polyester diols of 
.epsilon.-caprolactone having a molecular weight in the ran9e mentioned 
which have been prepared in known manner from a diol of the type mentioned 
by way of example above as starter molecule and .epsilon.-caprolactone. In 
the present case, hexane-1,6-diol is preferably used as this diol. 
Particularly preferred components (ii) are .epsilon.-caprolactone diols 
which have been prepared from hexane-1,6-diol as starter and which show a 
very narrow oligomer distribution. This can be achieved by the use of 
boron trifluoride etherate or organotin compounds as catalyst for the 
polymerization reaction. These particularly preferred ester diols have at 
least 50% by weight of molecules in the molecular weight range of 460 to 
802. 
In addition to these polyester diols, it is also possible, although less 
preferred, to use diols free from ester groups, for example those having a 
molecular weight of 62 to 300. Examples include ethane diol, 
butane-1,3-diol, 2,2,4-trimethylpentane-1,3-diol and, in particular, 
2-ethylhexane-1,3-diol. The molar ratio of diol free from ester groups to 
diol containing ester groups may be up to 1:1. 
In principle, the process according to the invention may be carried out 
analogously to known processes for the production of isocyanurate 
polyisocyanates. This means in particular that known trimerization 
catalysts of the type disclosed, for example, in the literature references 
cited above may be used. 
Quaternary ammonium hydroxides are preferably used as catalysts in the 
process according to the invention. Generally, it is possible to use any 
quaternary ammonium hydroxides known as trimerization catalysts for 
isocyanate groups. Suitable quaternary ammonium hydroxides include the 
quaternary ammonium hydroxides according to U.S. Pat. No. 3,487,080 
(herein incorporated by reference), column 2, lines 10 to 38, or 
EP-A-10,589, page 6, line 5 to page 8, line 10 (U.S. Pat. No. 4,324,879, 
herein incorporated by reference). Other suitable quaternary ammonium 
hydroxides include compounds corresponding to the formula 
##STR1## 
wherein R is a C.sub.1 -C.sub.20, preferably alkyl radical; a C.sub.7 
-C.sub.10, preferably C.sub.7 araliphatic hydrocarbon radical; or a 
saturated C.sub.4 -C.sub.10, preferably C.sub.5 -C.sub.6 cycloaliphatic 
hydrocarbon radical. 
Preferred catalysts include compounds corresponding to the formula 
##STR2## 
wherein R.sub.1, R.sub.2 and R.sub.3 may be the same or different and 
represent C.sub.1 -C.sub.18, preferably C.sub.1 -C.sub.4 alkyl radicals, 
more preferably methyl groups, and 
R.sub.4 is a benzyl, 2-hydroxyethyl, 2-hydroxypropyl or a 2-hydroxybutyl 
radical. 
Particularly preferred catalysts are N,N,N-trimethyl-N-benzyl ammonium 
hydroxide and N,N,N-trimethyl-N-(2-hydroxypropyl)-ammonium hydroxide. 
The optimum quantity of catalyst depends upon the nature of the catalyst 
and may be determined by a preliminary test. In the process according to 
the invention, the catalyst is generally used in a quantity of less than 
1% by weight, based on the starting diisocyanate used. When HDI, which has 
been substantially freed from carbon dioxide as previously discussed, is 
used as the starting diisocyanate and when the preferred ammonium 
hydroxide catalysts are used, the quantity of catalyst used is less than 
0.03% by weight, preferably less than 0.01% by weight and more preferably 
0.0005 to 0.005% by weight, based on the HDI used. 
The catalysts may be used in solvent-free form although they are preferably 
used in the form of dilute solutions. Suitable solvents are described in 
the cited publications. 
Trimerization and urethanization reactions are preferably carried out in 
the absence of solvents, although this does not preclude the use of 
standard lacquer solvents, for example, esters such as butyl acetate or 
ethoxyethyl acetate; ketones such as methyl isobutylketone or 
methylethylketone; hydrocarbons such a xylene; and mixtures of these 
solvents. However, since unreacted starting diisocyanate is subsequently 
removed, the additional use of such solvents results in unnecessary 
additional distillation. 
To complete the trimerization reaction, the catalyst is generally 
deactivated by heat and/or by the addition of a suitable catalyst poison 
to the reaction mixture. Suitable catalyst poisons, particularly when the 
preferred ammonium hydroxide catalysts are used, include inorganic acids 
such as hydrochloric acid, phosphorous acid or phosphoric acid; sulfonic 
acid or derivatives thereof such as methanesulfonic acid, 
p-toluenesulfonic acid or p-toluenesulfonic acid methyl or ethyl ester; 
and perfluorinated sulfonic acids such as nonafluorobutane sulfonic acid. 
Particularly suitable deactivators, i.e. catalyst poisons, include acidic 
esters of phosphorous acid or phosphoric acid such as dibutylphosphite, 
dibutylphosphate or di-(2-ethylhexyl)-phosphate, which are preferably used 
in the form of a dilute solution in HDI. The deactivators are generally 
added to the reaction mixture in a quantity at least equivalent to the 
catalyst. However, since the catalysts can partially decompose during the 
trimerization reaction, it is often sufficient to add a sub-equivalent 
quantity of the deactivator. When thermally labile catalysts such as 
quaternary ammonium hydroxides containing hydroxyalkyl substituents at the 
nitrogen are used, it is often unnecessary to add a catalyst poison 
because the reaction may be terminated by briefly heating the reaction 
mixture to temperatures above 100.degree. C. (thermal decomposition, i.e., 
deactivation of the catalyst). 
However, it is often advisable to use a larger than equivalent quantity, 
for example twice the equivalent quantity of deactivator, to guarantee 
complete termination of the reaction. Accordingly, it is preferred to use 
deactivators (catalyst poisons) in up to twice the equivalent quantity, 
based on the quantity of catalyst used. 
An important aspect of the invention is that, in addition to partial 
trimerization of the isocyanate groups of the starting diisocyanate, some 
of the isocyanate groups are modified by urethanization with the 
previously mentioned diols. The order in which urethanization and 
trimerization take place is immaterial provided that both process steps 
are carried out before removal of the excess starting diisocyanate. This 
means that the urethanization reaction with the diol (which consumes a 
portion of the isocyanate groups) can take place before the addition of 
the trimerization catalyst. The urethanization reaction may also be 
carried out with only part of the excess diisocyanate; more diisocyanate 
can then be added before the subsequent trimerization reaction. The 
urethanization and trimerization reactions may be carried out at the same 
time by adding diol and trimerization catalyst at the same time, for 
example in admixture. The urethanization reaction may begin before the 
trimerization reaction is fully completed, although it may also be 
initiated on completion of the trimerization reaction. The diol may also 
be added in portions at any time during the process. The trimerization and 
urethanization reactions should be completed before removing excess 
starting diisocyanate. 
The quantitative ratios between the individual reactants should be selected 
to ensure that the starting diisocyanate is used in such an excess that, 
on completion of the reaction, the reaction mixture still contains at 
least 10% by weight, preferably 35 to 70% by weight of unreacted starting 
diisocyanate, based on the mixture as a whole, not including any inert 
solvent used. The molar ratio of isocyanurate groups to urethane groups in 
the end products freed from excess starting diisocyanate is about 20:1 to 
0.2:1, preferably about 5:1 to 0.5:1. 
The process according to the invention is generally carried out at a 
temperature of about 0.degree. to 150.degree. C. The urethanization step, 
which may optionally be carried out separately at the beginning or at the 
end of the process, preferably takes place at about 20.degree. to 
150.degree. C., more preferably 80.degree. to 130.degree. C. The 
trimerization steps which optionally takes place separately before or 
after the urethanization step, preferably takes place at a temperature of 
about 0.degree. to 100.degree. C., more preferably about 20 to 80.degree. 
C. If the two reaction steps are carried out at the same time, the 
reaction temperatures are generally about 0.degree. to 100.degree. C., 
preferably about 40.degree. to 80.degree. C. The trimerization reaction is 
terminated thermally and/or by the addition of a catalyst poison, 
preferably after a degree of trimerization of about 10 to 40%, more 
preferably about 20 to 30% has been reached. The "degree of trimerization" 
is understood to be the percentage of isocyanate groups of the starting 
diisocyanate which reacts to form trimers; the urethanization step is 
disregarded in this calculation. However, it is essential that the 
reaction mixture still contains at least 10% by weight of unreacted 
starting diisocyanate on completion of urethanization and trimerization. 
On completion of the urethanization and trimerization reactions, the excess 
starting diisocyanate is separated off, optionally together with other 
volatile constituents present in the reaction mixture (such as solvent) by 
a suitable measure to a residual content of starting diisocyanate of at 
most 0.5% by weight. This can be done by thin-layer distillation or 
extraction, for example using n-hexane as extractant. 
The end products of the process according to the invention containing 
urethane and isocyanurate groups are liquid, substantially colorless 
polyisocyanates. The products of the process according to the invention, 
which are based on HDI, generally have an NCO content of about 6 to 20% by 
weight and a HAZEN color value (DIN 53 409) of less than 100, preferably 
less than 50. 
The products of the process according to the invention are soluble in 
standard solvents (such as esters, ketones and hydrocarbons, and may be 
diluted therewith without clouding) and are distinguished by high 
stability in storage. They are substantially free from secondary products. 
They are also eminently suitable for use as hardeners for two-component 
polyurethane lacquers, in which the usual polyether polyols, polyester 
polyols and/or polyacrylate polyols are present as polyhydroxyl compounds 
suitable as reactants for the polyisocyanates. Particularly preferred 
reactants for the products of the process according to the invention are 
polyacrylates containing hydroxyl groups, i.e., polymers or copolymers of 
alkyl(meth)acrylates, optionally with styrene or other copolymerizable 
olefinically unsaturated monomers. 
The two-component polyurethane lacquers, which contain combinations of such 
polyhydroxyl compounds as binders with the products of the process 
according to the invention as hardeners, may also contain the additives 
and auxiliaries normally used in lacquers such as pigments, levelling 
agents, catalysts, solvents and the like. The two-component polyurethane 
lacquers, which contain the products of the process according to the 
invention as hardeners, harden at room temperature or slightly elevated 
temperature to form lacquer films resistant to chemicals. 
The end products of the process according to the invention may also be 
blocked by blocking agents and used as hardeners in heat-crosslinkable 
one-component lacquers. Suitable blocking agents are known and include 
phenol; cresols; trimethylphenols; tert.-butylphenols; tertiary alcohols 
such as tert.-butanol, tert.-amyl alcohol and dimethylphenylcarbinol; 
compounds which readily form enols such as ethyl acetoacetate, acetyl 
acetone and malonic acid diethyl ester; secondary aromatic amines such as 
N-methylaniline, the N-methyltoluidines, N-phenyltoluidine and 
N-phenylxylidine; imides such as succinimide; lactams such as 
.epsilon.-caprolactam and 6-valerolactam; oximes such as butanone oxime 
and cyclohexanone oxime; mercaptans such as methyl mercaptan, ethyl 
mercaptan, butyl mercaptan, 2-mercaptobenzthiazole, .alpha.-naphthyl 
mercaptan and dodecyl mercaptan; and triazoles such as 1H-1,2,4-triazole. 
The end products of the process according to the invention may also be 
combined with polyamines wherein the amino groups may be blocked such as 
polyketimines, polyaldimines or oxazolidines. Under the influence of 
moisture, free amino groups (and in the case of the oxazolidine, free OH 
groups) are formed which react with the NCO groups to provide 
crosslinking. 
In these lacquer combinations, the polyisocyanate component and the 
reactant are present in such quantities that there are about 0.8 to 3, 
preferably about 0.9 to 1.8 (optionally blocked) isocyanate-reactive 
groups for each (optionally blocked) NCO group. 
Coating compositions containing the end products of the process according 
to the invention, optionally in blocked form, as hardeners are suitable 
for coating any substrates. They are distinguished from analogous coating 
compositions containing known polyisocyanates as hardeners by increased 
flexibility of the coatings. A particularly preferred application for the 
end products of the process according to the invention is as a hardener 
for two-component lacquers based on the polyhydroxyl compounds mentioned 
by way of example above, especially for the lacquering of flexible plastic 
moldings. The lacquers containing the polyisocyanates according to the 
invention provide films which also adhere surprisingly well to metallic 
substrates and show particular stability to light, a high heat distortion 
temperature and high abrasion resistance. They are also distinguished by 
extreme hardness, elasticity, very good resistance to chemicals, high 
gloss, excellent weather resistance and good pigmentability. 
In the following examples, all percentages are percentages by weight. 
EXAMPLES 
Example 1 
(Preparation of a catalyst solution) 
600 g 2-ethylhexane-1,3-diol were added to and stirred with 1000 g of a 
commercially available, colorless, 40% solution of 
N,N,N-trimethyl-N-benzyl ammonium hydroxide, in methanol. Methanol was 
completely removed with thorough stirring in a water jet pump vacuum at 
30.degree. to 40.degree. C. The 40% stock solution was diluted with 
additional 2-ethylhexane-1,3-diol to a concentration of 0.5%. 
Example 2 
(Preparation of a catalyst solution) 
60 g 2-ethylhexanol were added to 100 g of a 70% solution in methanol of 
N,N,N-trimethyl-N-(2-hydroxypropyl)-ammonium hydroxide, which was prepared 
by the reaction of trimethylamine with propylene oxide in methanol. 
Methanol was subsequently removed in a water jet pump vacuum. The stock 
solution was diluted with additional 2-ethylhexanol to a concentration of 
4%. The solution was brown in color. 
Example 3 
(Preparation of a diol) 
A melt at 120.degree. to 140.degree. C. from 2920 parts by weight adipic 
acid, 2910 parts by weight neopentyl glycol and 470 parts by weight 
hexane-1,6-diol. The temperature was then slowly increased to 180.degree. 
C. over a period of about 12 hours, during which time water was distilled 
off. The melt was then kept at 200.degree. C. for about 2 hours. 0.03 
parts by weight SnCl.sub.2.2H.sub.2 O were then added as catalyst, a 
vacuum was applied and the mixture was heated for about 15 hours to 
180.degree.-200.degree. C. 
A liquid, light yellow colored polyester having the following data was 
obtained: 
OH value: 225 (calculated 241) 
Acid value: 1 
Average molecular weight (calculated from hydroxyl number): 498 
Example 4 
(Preparation of a diol) 
57.3 kg .epsilon.-caprolactone, 12.7 kg hexane-1,6-diol and 3.5 g tin(II) 
octoate were mixed in a nitrogen-purged 1000 liter vessel and heated to 
160.degree. C. The reaction was complete after 4 hours at 160.degree. C. 
After cooling, the mixture (70 kg) was drained off; the product was liquid 
at room temperature. 
Data of the diol: 
.eta.25.degree. C.: 330 mPa.s 
OH value: 172.4 
Acid value: 0.6 
Color value (HAZEN) according to DIN 53 409: 30 
Average molecular weight (calc. from OH number): 650 
Analysis by gel chromatography revealed the following oligomer distribution 
of the polyester: 
______________________________________ 
Oligomer Experimental 
molecular weight 
(% surface area = % by weight) 
______________________________________ 
118 0.15 
232 1.75 
346 5.76 
460 11.44 
574 15.92 
688 19.19 
802 15.62 
916 12.08 
1030 8.15 
1144 5.25 
&gt;1144 4.69 
______________________________________ 
Result: more than 50% by weight of the molecules present in the polyester 
were in the molecular weight range of 460 to 802. 
Example 5 
(Invention) 
1596 g (9.5 mole) HDI were mixed in a suitable stirred vessel with 650 g (1 
mole) of the polyester diol of Example 4 and the resulting mixture was 
heated for 3 h at 90.degree. to 100.degree. C. The NCO content of the 
reaction mixture fell to 30.7%. 
A vigorous stream of pure nitrogen was then passed through the liquid for 
about 1 h at 40.degree. C., after which the liquid contained less than 5 
ppm (weight) dissolved carbon dioxide. More nitrogen was passed through 
the reaction mixture throughout the remainder of the reaction. 21.9 g 
(approx. 0.1095 g active substance=approx. 70 ppm) of the catalyst 
solution of Example 1 were then introduced dropwise over a period of 15 to 
30 minutes, followed by heating for 30 minutes to a temperature of 
65.degree. to 70.degree. C. which was then maintained for 2.5 hours. When 
the NCO content of the crude product was 22.8%, 0.22 g of a 25% solution 
of dibutylphosphate in HDI is added, followed by stirring for 15 minutes 
at 60.degree. C. After cooling to about 23.degree. C., excess HDI was 
removed by distillation in a short-path evaporator. 610 g HDI were 
recovered and 1630 g of a viscous colorless liquid having the following 
characteristic data were obtained: 
NCO content: 11.85% 
Viscosity: 9500 mPa.s/23.degree. C. 
Free HDI: 0.07% 
Color value (HAZEN) according to DIN 53 409: 30 
The molar ratio of urethane groups to isocyanurate groups in the product 
was about 2:1 (calculated). 
Example 6 
The procedure was as described in Example 5 using the following quantities: 
2100 g (12.5 mole) HDI 
250 g (0.5 mole) of the polyester diol of Example 3 
24.3 g of the catalyst solution of Example 1 
0.3 g 25% solution of dibutylphosphate in HDI. 
After removal of unreacted HDI, 968 g of a colorless liquid having the 
following data were obtained: 
NCO content: 16.7% 
Viscosity: 4500 mPa.s/23.degree. C. 
Free HDI: 0.12% 
Color value (HAZEN) according to DIN 53 409: 40 
The calculated molar ratio of urethane groups to isocyanurate groups in the 
product was about 1:1. 
Example 7 
The procedure was as in Example 5 using the following quantities: 
1428 g (8.5 mole) HDI 
250 g (0.5 mole) of the polyester of Example 3 
19.6 g of the catalyst solution of Example 1 
0.2 g 25% solution of dibutylphosphate in HDI 
After the reaction was terminated at an NCO content of the mixture of 
31.8%, excess HDI was removed and 1014 g of a colorless liquid having the 
following data were obtained: 
NCO content: 15.5% 
Viscosity: 7500 mPa.s/23.degree. C. 
Free HDI: 0.09% 
Color value (HAZEN) according to DIN 53 409: 30 
The calculated molar ratio of urethane to isocyanurate group was about 1:1. 
Example 8 
(Invention, alternative embodiment) 
1596 g (9.5 mole) HDI were heated to 50.degree. C. in a suitable stirred 
vessel and freed from carbon dioxide by passing nitrogen through the 
liquid until the residual content of carbon dioxide was less than 5 ppm 
(weight). 6.5 g of the catalyst of Example 2 were then added; the 
temperature rose to 60.degree. C. This temperature was maintained for 
about 6 h, at which time the NCO content had fallen to 40.5%. The catalyst 
was deactivated by heating the mixture for 10 minutes to 120.degree. C. 
650 g of the polyester diol of Example 4 were then poured into the liquid, 
followed by stirring for 4 hours at 90.degree. to 100.degree. C. The NCO 
content was then 23.0%. Monomeric HDI was removed by thin-layer 
distillation at 120.degree. C. in a short-path evaporator. 1585 g of a 
viscous liquid having the following characteristic data were obtained: 
NCO content: 12.1% 
Viscosity: 10,500 mPa.s/23.degree. C. 
Free HDI: 0.1% 
Color value (HAZEN) according to DIN 53 409: 50 
Example 9 
(Invention) 
798 g (4.75 mole) HDI were reacted as in Example 5 with 244 g (0.375 mole) 
of the diol of Example 4 and 18 g (0.125 mole) of 
cyclohexane-1,4-dimethanol. Using 10 g of the catalyst solution of Example 
1, the mixture was then trimerized as in Example 5 to an NCO content of 
26.9%, after which the reaction was terminated by the addition of 0.12 g 
of a 25% solution of dibutylphosphate in HDI. Removal of monomeric HDI by 
distillation provided 680 g of a viscous liquid having the following 
properties: 
NCO content: 12.8% 
Viscosity: 4700 mPa.s/23.degree. C. 
Free HDI: 0.04% 
Color value (HAZEN) according to DIN 53 409: 40 
The calculated molar ratio of urethane to isocyanurate was about 2:1. 
Examples 10 to 15 
(Invention) 
The procedure in Examples 10 to 12 was the same as in Example 5, i.e., 
first urethanization and then trimerization. In Examples 13 to 15, the 
procedure was the same as in Example 8, i.e., first trimerization and then 
urethanization. Catalysis and termination as described in Examples 5 and 
8. The reaction data and characteristics of the end products are shown in 
the following Table. 
TABLE 1 
__________________________________________________________________________ 
NCO con- 
Quantity 
NCO content 
HAZEN 
Quantity 
Quantity 
tent on ter- 
of product 
of the pro- 
color value Molar Ratio 
of HDI 
of diol of 
mination of 
after removal 
duct/viscos- 
acc. to 
Free HDI 
urethane 
Example 
used Ex. 4 used 
the reaction 
of HDI ity at 23.degree. C. 
DIN 53409 
content 
isocyanurate 
__________________________________________________________________________ 
10 672 g 
41 g 35.0% 335 g 17.4%/ 80 0.04 1:4 
5500 mPa .multidot. s 
11 714 g 
83 g 32.5% 418 g 16.3%/ 50 0.07 1:2 
6000 mPa .multidot. s 
12 798 g 
166 g 27.0% 615 g 14.7%/ 30 0.04 1:1 
10000 mPa .multidot. s 
13 672 g 
41 g 38.4% 270 g 17.0%/ 90 0.1 1:4 
3000 mPa .multidot. s 
14 714 g 
83 g 34.0% 375 g 16.8%/ 40 0.12 1:2 
4200 mPa .multidot. s 
15 798 g 
166 g 32.4% 450 g 13.1%/ 40 0.05 1:1 
3000 mPa .multidot. s 
__________________________________________________________________________ 
Example 16 
(Application Example) 
The two polyisocyanates according to Examples 5 and 15 were used in 
combination with a hydroxylpolyacrylate as a lacquer binder for coating an 
elastic plastic in comparison with two known polyisocyanates. 
The hydroxypolyacrylate used was a 65% solution in xylene of a copolymer of 
18% by weight styrene, 26% by weight hydroxyethyl acetate, 55% by weight 
butylacrylate and 1% acrylic acid. The solution had a hydroxyl value of 
72, an acid value of 5.9 and a viscosity of 2300 mPa.s/23.degree. C. 
The HDI-based isocyanurate polyisocyanate obtained according to example 2 
of U.S. Pat. No. 4 324 879 which was not diol-modified (A) and a 
diol-modified isocyanurate polyisocyanate (B), again based on HDI, 
prepared in accordance with Example 9 of DE-OS 3,219,608 were used as 
comparison polyisocyanates. 
Polyisocyanate (A) in solvent-free form had an NCO content of 21.8% and a 
viscosity of 4000 mPa.s/23.degree. C., while polyisocyanate (B) had an NCO 
content of 19.0% and a viscosity of 11,500 mPa.s at 23.degree. C. 
The compositions were used to coat sheets of a semi-rigid, elastic PUR 
integral foam plastic. The sheets had been pretreated with a primer. 
The composition of polyisocyanate and hydroxyl component was mixed to 
provide an NCO:OH equivalent ratio of 1:1. A TiO.sub.2 pigment (of the 
rutile type) was incorporated in the hydroxyl component in known manner, 
i.e., on a three-roll mixer. The ratio by weight of organic binder to 
pigment in the ready-to-spray coating was 1.5. 0.3% by weight (based on 
binder) diazabicyclooctane was added as catalyst. 
The mixtures were adjusted with more solvent to an outflow time (DIN 53 
211, 4 mm of approximately 20 seconds. The pot life of these 
ready-to-spray lacquers in a closed container was at least 20 seconds. 
They were sprayed onto the plastic sheets and the properties were 
determined. The results are shown in Table 2 below. The adhesion, gloss 
and impact elasticity of the lacquer films are not shown. In each case, 
they are of a high level. 
TABLE 2 
__________________________________________________________________________ 
Lacquer 
Lacquer 
Laquer 
Lacquer 
containing 
containing 
containing 
containing 
comparison 
comparison 
polyiso- 
polyiso- 
polyiso- 
polyiso- 
cyanate of 
cyanate of 
Test cyanate (A) 
cyanate (B) 
Example 5 
Example 15 
__________________________________________________________________________ 
Pendulum hardness (s) (DIN 53157) after 
45 mins/80.degree. C. 
32 35 28 27 
7 days/approx. 23.degree. C. 
100 120 105 50 
14 days/approx. 23.degree. C. 
125 130 110 83 
14 days/approx. 23.degree. C. + 
130 135 120 90 
30 mins at 80.degree. C. 
Dissolvability after storage of the lacquer 
film for 45 mins at 80.degree. C. and 14 days at 
approx. 23.degree. C. (1) 
Toluene 2 2 2 1-2 
Methoxypropyl acetate 
1 1 1-2 2 
Ethyl acetate 2 2-3 2-3 3 
Acetone 3 3 2-3 2-3 
Folding test at various temperatures/ 
1 inch (= 2.54 cm) (2) 
+20.degree. C. + + + + 
+5.degree. C. + + + + 
0.degree. C. 0 - + + 
-5.degree. C. - - + + 
-10.degree. C. - - + + 
-15.degree. C. - - + + 
-20.degree. C. - - + + 
-40.degree. C. - - - + 
__________________________________________________________________________ 
+ = O.K., 0 = incipient cracking, - = cracked 
Explanation of Table 2 
(1) The dissolvability of the lacquer films was evaluated after 1 minute in 
contact with the solvent. The damage to the lacquer film was evaluated in 
6 stages from 0=lacquer film was completely unchanged to 5=lacquer film 
dissolved. 
(2) The folding test was carried out with the PUR sheets. After the 
lacquers were sprayed onto the primed and lightly abraded sheets, they 
were briefly aired, baked for 45 minutes at 80.degree. C. and then aged 
for 1 week at approximately 23.degree. C. 2 cm wide strips were then cut 
and stored for about 30 minutes at the particular measuring temperatures. 
The strips were then bent around a 1 inch mandrel which was maintained at 
the particular measuring temperature. The test was also conducted at the 
particular measuring temperature (in a cold chamber). 
Evaluation of the test specimens: 
+: film O.K. 
0: incipient cracking 
-: cracked 
Example 17 
This Example investigated the advantages which the polyisocyanates 
according to the invention afford in regard to long-term storage in 
standard lacquer solvents. The two polyisocyanates of Examples 5 and 15 
were again compared with polyisocyanates (A) and (B). The long-term 
storage took place at room temperature in sealed glass bottles, which were 
visually examined, in the following solvents: methoxypropyl acetate (MPA), 
ethyl glycol acetate (EGA), xylene (X), butyl acetate (BA) and ethyl 
acetate (EA). The results are shown in Table 3. 
TABLE 3 
__________________________________________________________________________ 
7 days 
14 days 
21 days 
28 days 
2 months 
4 months 
Solvent 
Polyisocyanate 
35% 
30% 
35% 
30% 
35% 
30% 
35% 
30% 
35% 
30% 
35% 
30% 
__________________________________________________________________________ 
MPA (A) 0 0 0 0 0 1 1 1-2 
-- -- -- -- 
(B) 0 0 0 1 0 2 1 2 -- -- -- -- 
of Example 5 
0 0 0 0 0 0 0 0 0 0 0 0 
of Example 15 
0 0 0 0 0 0 0 0 0 0 0 0 
EGA (A) 0 0 0 0 0 0 1 2 -- -- -- -- 
(B) 0 0 0 0 1 2 -- -- -- -- -- -- 
of Example 5 
0 0 0 0 0 0 0 0 1 1 -- -- 
of Example 15 
0 0 0 0 0 0 0 0 0 0 0 1 
X (A) 0 0 0 0 0 0 1 2 -- -- -- -- 
(B) 0 0 1 2 -- -- -- -- -- -- -- -- 
of Example 5 
0 0 0 0 0 1 0 1 -- -- -- -- 
of Example 15 
0 0 0 0 0 0 0 1 -- -- -- -- 
BA (A) 0 0 0 1 1 2 -- -- -- -- -- -- 
(B) 0 0 0 1 1 2 -- -- -- -- -- -- 
of Example 5 
0 0 0 0 0 0 0 0 0 1 0 1 
of Example 15 
0 0 0 0 0 0 0 1 0 2 0 1 
EA (A) 0 0 1 0 1 0 1 1 -- -- -- -- 
(B) 0 0 0 0 1 1 2 1 -- -- -- -- 
of Example 5 
0 0 0 0 0 0 0 0 0 1 0 1 
of Example 15 
0 0 0 0 0 0 0 0 1 0 1 1 
__________________________________________________________________________ 
Explanation of the Table: 0 = 0.K., clear solution; 1 = incipient 
clouding; 2 = clouded 
Summary of the results of Examples 16 and 17 
The lacquer polyisocyanates to the invention are distinguished from the 
prior art by the fact that they provide lacquer films which show higher 
elasticity and, above all, higher flexural elasticity at low temperatures. 
At the same time, the slightly lower surface hardness is still entirely 
adequate for all practical applications. The products obtained by the 
process according to the invention are also distinctly superior in storage 
in dilute solutions, which is indicative of their high compatibility. 
Although the invention has been described in detail in the foregoing for 
the purpose of illustration, it is to be understood that such detail is 
solely for that purpose and that variations can be made therein by those 
skilled in the art without departing from the spirit and scope of the 
invention except as it may be limited by the claims.