Urethane prepolymer and polyurethane compositions comprising the prepolymer

A urethane prepolymer useful for preparing paints, coating agents, adhesives, etc., is obtained by reacting a di-isocyanate with a tetra-functional polyol prepared by reacting erythritol with an alkylene oxide or lactone.

This invention relates to a urethane prepolymer used for preparing a paint, 
coating agent, adhesive, or the like, and also to a polyurethane 
composition prepared by using such a prepolymer, in particular a paint, a 
coating agent or an adhesive. 
A two-pack urethane paint, coating agent, or adhesive is a two-component 
system comprising a urethane prepolymer having isocyanate groups, and a 
polyol. There are known two major classes of urethane prepolymers having 
isocyanate groups, i.e. (1) adducts obtained by reacting polyhydric 
alcohols such as trimethylolpropane, or water with di-isocyanates, and (2) 
isocyanurates obtained by the cyclic trimerization of di-isocyanates by 
catalysts. These urethane prepolymers generally contain not more than 
three isocyanate groups in a molecule on average. The urethane prepolymers 
give polyurethane compositions if mixed with polyols, etc. The 
polyurethane compositions are hardened by urethane reaction (crosslinking) 
to exhibit such physical properties as desired. There is a need for 
polyurethane compositions which can be hardened at a higher rate and 
exhibit better physical properties when hardened. 
Processes including preparing multifunctional urethane prepolymers are 
known as one of the approaches to the manufacture of polyurethane 
compositions giving excellent physical properties when hardened. It has, 
for example, been proposed that pentaerythritol containing four functional 
groups, dipentaerythritol containing six functional groups, or sucrose 
containing eight functional groups be used as the polyhydric alcohol 
feedstock, and be reacted directly with a di-isocyanate to prepare a 
urethane prepolymer containing four to eight isocyanate groups per 
molecule. These polyhydric alcohols have, however, been difficult to react 
uniformly with di-isocyanates, since their compatibility with 
di-isocyanates is low and their melting points are high. Therefore, 
attempts have been made to react di-isocyanates with polyols prepared by 
the addition reaction of polyhydric alcohols with alkylene oxides to 
improve the compatibility of polyhydric alcohols with di-isocyanates. The 
polyhydric alcohols have, however, been difficult to react directly with 
alkylene oxides, since they have high melting points and have low 
solubility. It has, therefore, been usual practice to use alkylene oxides 
diluted with glycerol, water, or the like. It has been possible, however, 
to obtain only an adduct of low purity and it has been difficult to 
prepare satisfactory urethane prepolymers, since the reaction of 
di-isocyanates with any such adduct has resulted in the formation of a 
gel, or a product having too few functional groups. 
U.S. Pat. Nos. 2,778,885; and 3,291,865 and Japanese Patent Application 
Laid-Open No. 51-93995 disclose processes for manufacturing polyols by 
reacting erythritol with epoxy compounds, such as alkylene oxides. U.S. 
Pat. No. 2,778,855, however, describes only a process for manufacturing 
polyols and does not contain any disclosure of the specific use of these 
polyols. U.S. Pat. No. 3,291,865 does suggest the application of polyols 
to the manufacture of polyurethanes, etc., but does not describe any 
specific example of such an application. Japanese Patent Application Laid 
Open No. 51-93995 describes a process for manufacturing urethane foams 
from polyols directly in a single step, but does not disclose any process 
for reacting polyols with di-isocyanates to prepare urethane prepolymers. 
It does not teach any use of polyols for purposes other than the 
manufacture of foams, either. 
There is known a polyether polyol prepared by adding propylene oxide to 
ethylenediamine and containing four functional groups. This polyol, 
however, is likely to form a gel as a result of a side reaction during the 
synthesis of a prepolymer, since it contains tertiary nitrogen. The 
polyurethane composition manufactured using this polyol is easily degraded 
by oxidation, is undesirably colored, and is unstable to heat. 
Other possible polyhydric alcohols include condensation polyester polyols 
having low molecular weight, and acrylic polyols produced by the 
polymerization of acrylic monomers and having low molecular weight. The 
mechanism of the reaction which is involved, however, makes it difficult 
always to produce any polyhydric alcohol of this type containing four or 
five hydroxyl groups in a molecule. 
It is an object of this invention to provide a urethane prepolymer which 
can be hardened rapidly and yield a hardened product having excellent 
properties, and a polyurethane composition comprising such a urethane 
prepolymer and a polyol, particularly a two-pack composition used as, for 
example, a paint, a coating agent or an adhesive. 
This object is attained by a urethane prepolymer containing isocyanate 
groups which is obtained by reacting erythritol with 2 to 8 mols of an 
alkylene oxide or lactone per mol of erythritol to prepare a polyol 
containing four functional groups, and by reacting the polyol with a 
di-isocyanate in a reaction equivalent ratio (isocyanate groups/hydroxyl 
groups) of 3-20, and by a polyurethane composition which is prepared from 
any such prepolymer and a polyol. 
The urethane prepolymer of this invention is a prepolymer containing 
isocyanate groups and obtained by reacting erythritol with 2 to 8 mols of 
an alkylene oxide or lactone per mol of erythritol to prepare a polyol 
containing four functional groups, and by reacting the polyol with a 
di-isocyanate in a reaction equivalent ratio (isocyanate groups/hydroxyl 
groups) of 3-20. 
The polyurethane composition of this invention is a composition comprising 
any urethane prepolymer of this invention and a polyol. 
The erythritol which is used for the purpose of this invention is a tetrose 
alcohol having a molecular weight of 122 and the empirical formula C.sub.4 
H.sub.10 O.sub.4. There are three isomers: D-erythritol, L-erythritol and 
mesoerythritol. Mesoerythritol, which has the structural formula 
##STR1## 
and a melting point of 121.5.degree. C., can be manufactured at a low cost 
by a variety of methods such as the breakdown of glucose or n-paraffin by 
fermentation, the reduction of tartartic acid, and a process which 
comprises oxidizing cellulose or starch with periodic acid, hydrogenation 
and hydrolysis. 
D-erythritol and L-erythritol, neither of which occurs naturally, can both 
be synthesized by, for example, reducing erythrose. They both have a 
melting point of 88.degree. C. and can be used like mesoerythritol. A 
mixture of the D- and L-forms (racemic form) can also be used. 
The melting points of erythritol are lower than those of other 
multifunctional polyols, e.g. pentaerythritol (m.p. over 180.degree. C.) 
and sucrose (m.p. 187.degree. C.). Erythritol has good solubility in 
alkylene oxides and lactones. The addition reaction between erythritol and 
any alkylene oxide or lactone, therefore, does not call for the addition 
of any solvent, such as glycerol or water, or the use of a temperature 
that is so high as to be likely to cause an explosion. A polyol of high 
purity containing four functional groups can be synthesized easily by 
reaction at a temperature which is as low as, say, between 100.degree. C. 
and 180.degree. C. If the polyol is reacted with a di-isocyanate, a 
desired multifunctional prepolymer containing isocyanate groups can be 
obtained easily without undergoing any gelatinization. 
Ethylene oxide, propylene oxide, 1,2-butylene oxide and 2,3-butylene oxide 
are examples of the alkylene oxides which can be used for reaction with 
erythritol in accordance with this invention. Ethylene or propylene oxide 
is preferably used. 
An average of 2 to 8 mols of alkylene oxide is preferably reacted with 1 
mol of erythritol. The use of the alkylene oxide in a proportion below 2 
mols gives a polyol having low compatibility with the di-isocyanate, and 
results in failure to produce a uniform urethane prepolymer. The use of 
alkylene oxide in a proportion above 8 mols is also undesirable, as it 
results in the formation of a urethane prepolymer having too low an 
isocyanate content. 
The addition reaction between erythritol and alkylene oxide can be 
performed by any known method employing, for example, an acid or alkali 
catalyst. 
The lactone which can be used for reaction with the erythritol in 
accordance with this invention is a compound containing a five- or 
more-membered ring, i.e. one having four or more carbon atoms in the ring. 
Specific examples are .epsilon.-caprolactone, 
.gamma.-methyl-.delta.-valerolactone, .delta.-valerolactone and 
.gamma.-butyrolactone. .epsilon.-Caprolactone is, among others, preferred. 
An average of 2 to 8 mols of lactone is preferably reacted with 1 mol of 
erythritol. The use of the lactone in a proportion below 2 mols gives a 
polyol having low compatibility with the di-isocyanate, and results in 
failure to produce a uniform urethane prepolymer. The use of the lactone 
in any proportion above 8 mols is also undesirable, as it results in the 
formation of a urethane prepolymer having too low an isocyanate content. 
Any method that is itself known in the art can be employed for causing the 
addition reaction between the erythritol and the lactone. The reaction 
can, for example, be easily accomplished if the mixture of reactants is 
heated to a temperature of 100.degree. C. to 220.degree. C. with stirring 
in the presence or absence of a catalyst comprising an organic titanium 
compound such as tetrabutyl titanate, an organic tin compound such as 
dibutyltin dilaurate, or a metal such as sodium or potassium. 
Examples of the di-isocyanate to be reacted with the polyol containing four 
functional groups which is obtained as the product of the addition 
reaction between erythritol and alkylene oxide or lactone, include 
2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane 
diisocyanate, naphthalene-1,5-diisocyanate, xylylene diisocyanate, 
isophorone diisocyanate, hexamethylene diisocyanate, and 
4,4'-methylenebiscyclohexyl isocyanate. 
The reaction between the polyol and the diisocyanate is preferably carried 
out in a mixture thereof having an equivalent ratio of isocyanate/hydroxyl 
groups ranging between 3 and 20. If the ratio is below 3 the reaction is 
likely to yield a urethane prepolymer having a high molecular weight, or 
even a gelated product. If the ratio is over 20 a large amount of 
diisocyanate remains unreacted and its removal is very difficult. 
The other conditions for the urethane reaction depend on the polyol and 
diisocyanate which are employed. For example, it is possible to use a 
solvent which is unreactive with the isocyanate group, such as methyl 
ethyl ketone, ethyl acetate, methyl isobutyl ketone or acetone, or 
alternatively, no solvent is used. The reaction temperature may be 
selected from the range of 0.degree. C. to 100.degree. C. If required, it 
is possible to use a catalyst which is usually employed for urethanation, 
such as dibutyltin dilaurate, dibutyltin octoate, N-ethylmorpholine or 
triethylenediamine. 
After the urethane reaction has finished the unreacted diisocyanate monomer 
is removed from the reaction product by, for example, thin-film 
distillation or solvent extraction. It is desirable that the urethane 
prepolymer does not contain more than 1% by weight of diisocyanate 
monomer, as its vapor is toxic. It is, however, necessary to perform 
distillation, etc. under strictly controlled conditions, since the 
urethane prepolymer is likely to undergo reaction to a high molecular 
substance, such as allophanation, upon exposure to a high temperature. 
Examples of the polyol which is used with the urethane prepolymer to form 
the polyurethane composition of this invention include polyester polyols, 
polyether polyols, oil-modified polyester polyols, acrylic polyols and 
urethane elastomers containing hydroxyl groups. 
The polyurethane composition of this invention may further comprise a 
polyamine. Examples of the polyamines which can be used include 
polyethylene polyamines, polypropylene polyamines, and polyamides which 
are obtained by reacting polymerized fatty acids and polyamines. 
The polyurethane composition of this invention comprises a mixture of 
urethane prepolymer and polyol giving an equivalent ratio of 
isocyanate/hydroxyl groups (which may hereinafter be stated as (NCO/OH)) 
ranging between 0.5 and 2.0. If the ratio is below 0.5 the composition 
fails to be satisfactorily crosslinked and yields a hardened product which 
is low in hardness, and chemical and solvent resistance. If the ratio is 
over 2.0, the composition yields a hardened product which is brittle and 
of low impact resistance. 
The polyurethane composition of this invention is usually supplied as a 
two-pack composition, i.e., the urethane prepolymer and the polyol are 
mixed to form the composition immediately prior to its use. 
The polyurethane composition of this invention is usually diluted with a 
solvent, etc. when it is used, though it can also be used without being 
diluted, or in a solventless form. For diluting the composition it is 
possible to use a solvent which is unreactive with the isocyanate group, 
for example, ethyl or butyl acetate, acetone, methyl ethyl ketone, xylene, 
dioxan or Cellosolve acetate. It is also possible to use as the diluent a 
plasticizer such as dibutyl phthalate or octoate. 
The composition may further contain a catalyst for promoting its hardening, 
if required. It is possible to use as the catalyst, for example, an 
organic metal compound such as dibutyltin dilaurate, dibutyltin dioctoate, 
tetrabutyl-1,3-diacetoxy-distannoxan, stannous octoate, lead naphthenate 
or ferric acetylacetonate, or a tertiary amine such as triethylenediamine. 
If any such catalyst is used, its proportion is from 0.01 to 3% by weight 
of the prepolymer. 
It is also possible to add to the polyurethane composition of this 
invention any of various pigments including azo pigments, copper 
phthalocyanine pigments, other organic and inorganic color pigments such 
as red oxide, chrome yellow, titanium dioxide, zinc white and carbon 
black, rust-preventing pigments such as minimum, lead white, basic 
chromates, basic lead sulfate, zinc chromate and zinc dust, and extender 
pigments such as clays, silica, talc, calcium carbonate and micas, if 
required. It is also possible to add various kinds of agents including 
leveling agents and silane or titanium coupling agents, if required. It is 
further possible to add xylene, vinyl chloride, cellulosic, acrylic, and 
other resins to the extent that they do not adversely affect the physical 
properties of the composition. 
The polyurethane composition of this invention is particularly suitable for 
use as a paint, coating agent, or adhesive. It can be used at normal 
temperatures or by heating to a temperature of 50.degree. C. to 80.degree. 
C. for application by, for example, spraying or roll coating onto a metal, 
a film, a molded product of plastics, cloth, etc. The film formed by the 
composition can be hardened if it is allowed to dry at room temperature, 
or heated to a temperature of 80.degree. C. to 250.degree. C. 
The polyurethane composition of this invention can be hardened rapidly and 
yield a hardened product having a high crosslinking density and excellent 
physical properties including hardness, chemical and solvent resistance, 
and adhesiveness. Therefore, it provides an excellent paint, coating 
agent, or adhesive. 
The invention will now be described more specifically with reference to 
examples relating to the synthesis of polyols and urethane prepolymers, 
examples of polyurethane compositions and comparative examples.

POLYOL SYNTHESIS EXAMPLE 1 
The synthesis of a polyol was carried out by an addition reaction employing 
mesoerythritol and propylene oxide in a molar ratio of 1:4. 
A reaction vessel was charged with 122.1 g of mesoerythritol, 232.2 g of 
propylene oxide and 10.6 g of potassium hydroxide and the mixture thereof 
was heated at 60.degree. C. for an hour and at 110.degree. C. for eight 
hours with stirring to undergo reaction. When the reaction had been 
completed dry nitrogen gas was blown into the reaction product to remove 
the unreacted propylene oxide and water which remained to some extent. 
Then, phosphoric acid was added to the reaction product to neutralize the 
potassium hydroxide and the alkali was completely removed by filtration, 
whereby a tetrafunctional polyol having a hydroxyl number of 633 and an 
acid value of 0.02 was obtained as the product of the addition reaction 
between mesoerythritol and propylene oxide. 
POLYOL SYNTHESIS EXAMPLE 2 
In this example, mesoerythritol and propylene oxide were employed in a 
molar ratio of 1:6 and the reaction vessel was charged with 122.1 g of 
mesoerythritol, 348.3 g of propylene oxide and 14.1 g of potassium 
hydroxide. Then, the reaction and treatment of Synthesis Example 1 were 
repeated to yield an adduct having a hydroxyl number of 477 and an acid 
value of 0.02. 
POLYOL SYNTHESIS EXAMPLE 3 
In this example, mesoerythritol and ethylene oxide were employed in a molar 
ratio of 1:2.5 and the reaction vessel was charged with 122.1 g of 
mesoerythritol, 110.0 g of ethylene oxide and 7.0 g of potassium 
hydroxide. Then, the reaction and treatment of Synthesis Example 1 were 
repeated to yield an adduct having a hydroxyl number of 967 and an acid 
value of 0.02. 
POLYOL SYNTHESIS EXAMPLE 4 
An addition reaction was caused to take place between mesoerythritol and 
caprolactone employed in a molar ratio of 1:2.5. The reaction vessel was 
charged with 122.1 g of mesoerythritol, 285.4 g of .epsilon.-caprolactone 
and 0.004 g of tetrabutyl titanate and they were reacted at 170.degree. C. 
for 10 hours with stirring to yield an adduct between mesoerythritol and 
caprolactone (tetrafunctional polyol) having a hydroxyl number of 551 and 
an acid value of 0.4. 
POLYOL SYNTHESIS EXAMPLE 5 
In this example, mesoerythritol and caprolactone were employed in a molar 
ratio of 1:6 and the reaction vessel was charged with 122.1 g of 
mesoerythritol, 684.8 g of .epsilon.-caprolactone and 0.01 g of tetrabutyl 
titanate. Then, the reaction of Synthesis Example 4 was repeated to yield 
an adduct having a hydroxyl number of 278 and an acid value of 0.3. 
POLYOL SYNTHESIS EXAMPLE 6 
In this example, mesoerythritol and propylene oxide were employed in a 
molar ratio of 1:1.5 and the reaction vessel was charged with 122.1 g of 
mesoerythritol, 87.1 g of propylene oxide and 6.3 g of potassium 
hydroxide. Then, the reaction and treatment of Synthesis Example 1 were 
repeated to yield an adduct having a hydroxyl number of 1072 and an acid 
value of 0.03. 
POLYOL SYNTHESIS EXAMPLE 7 
In this example, mesoerythritol and propylene oxide were employed in a 
molar ratio of 1:9. The reaction vessel was charged with 122.1 g of 
mesoerythritol, 522.5 g of propylene oxide and 19 g of potassium hydroxide 
and the reaction and treatment of Synthesis Example 1 were repeated to 
yield an adduct having a hydroxyl number of 348 and an acid value of 0.02. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLE 1 
A reaction vessel was charged with 1740 g of raw diisocyanate consisting of 
2,4-tolylene diisocyanate and 2,6-tolylene diisocyanate mixed in a weight 
ratio of 80/20 (hereinafter referred to as "80-TDI") and 354 g of polyol 
which had been obtained in Polyol Synthesis Example 1 and they were 
reacted by heating at 55.degree. C. for eight hours with stirring. The 
(NCO/OH) value was 5. 
The solution obtained as the reaction product was subjected to thin-film 
distillation at a temperature of 165.degree. C. and a pressure of 1 mm Hg, 
whereby the unreacted tolylene diisocyanate monomers were removed and a 
urethane prepolymer was obtained. The urethane prepolymer was dissolved in 
ethyl acetate to form a urethane prepolymer solution having a 
concentration of 70% by weight. The urethane prepolymer solution was found 
to contain 10.1% by weight of NCO and 0.3% by weight of unreacted tolylene 
diisocyanate monomer. 
The conditions employed for the preparation of the prepolymer and the 
characteristics of its solution are shown in TABLE 1. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLES 2 TO 4 
Synthesis Example 1 was followed to prepare urethane prepolymer solutions, 
except that the conditions were altered as shown in TABLE 1. The (NCO/OH) 
value was 5 in all of the examples. The characteristics of the solutions 
are shown in TABLE 1. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLE 5 
1740 g of 80-TDI and 408 g of polyol which had been obtained in Polyol 
Synthesis Example 4 were reacted at 55.degree. C. for eight hours. The 
(NCO/OH) value was 5. 
The solution obtained as the reaction product was subjected to thin-film 
distillation at a temperature of 165.degree. C. and a pressure of 1 mm Hg, 
whereby the unreacted tolylene diisocyanate monomers were removed and a 
urethane prepolymer was obtained. The prepolymer was dissolved in ethyl 
acetate to form a urethane prepolymer solution having a concentration of 
70% by weight. The solution was found to contain 9.5% by weight of NCO and 
0.3% by weight of unreacted tolylene diisocyanate monomer. 
The conditions employed for the preparation of the prepolymer and the 
characteristics of its solution are shown in TABLE 2. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLES 6 TO 8 
Synthesis Example 5 was followed to prepare urethane prepolymer solutions, 
except that the conditions were altered as shown in TABLE 2. The (NCO/OH) 
value was 5 in all of the examples. The characteristics of the solutions 
are shown in TABLE 2. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLE 9 
An attempt was made to react at 55.degree. C. 870 g of 80-TDI and 354.3 g 
of polyol which had been obtained in Polyol Synthesis Example 1, but a gel 
was formed before the reaction was complete. This was apparently due to 
the fact that the (NCO/OH) value was as low as 2.5. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLE 10 
730.8 g of 80-TDI and 35.4 g of the polyol which had been obtained in 
Polyol Synthesis Example 1 were reacted at 55.degree. C. for eight hours. 
The (NCO/OH) value was 21. The reaction product was a solution consisting 
of 15% by weight of urethane prepolymer and as much as 85% by weight of 
80-TDI. The removal of the unreacted TDI monomers took a great deal of 
time. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLE 11 
The reaction vessel was charged with 1740 g of 80-TDI and 209.2 g of polyol 
which had been obtained in Polyol Synthesis Example 6. Although an attempt 
was made to react them at 55.degree. C., no uniform reaction took place, 
but a turbid solution was formed. When the stirring of the solution was 
discontinued solid matter settled as a gel which was insoluble in ethyl 
acetate. The (NCO/OH) value was 5. 
URETHANE PREPOLYMER SYNTHESIS EXAMPLE 12 
The reaction vessel was charged with 1740 g of 80-TDI and 645 g of polyol 
which had been obtained in Polyol Synthesis Example 7, and they were 
reacted at 55.degree. C. for eight hours. The (NCO/OH) value was 5. 
The solution obtained as the reaction product was subjected to thin-film 
distillation at 165.degree. C. and 1 mm Hg, whereby the unreacted TDI 
monomers were removed and a urethane prepolymer was obtained. The 
prepolymer was dissolved in ethyl acetate to form a urethane prepolymer 
solution having a concentration of 70% by weight. The solution was found 
to contain 7.7% by weight of NCO and 0.6% by weight of unreacted monomer. 
TABLE 1 
__________________________________________________________________________ 
Examples of Urethane Prepolymers 
1 2 3 4 
__________________________________________________________________________ 
Conditions for 
Amounts for 
80-TDI 1740 
1740 
-- -- 
preparation of 
materials 
Isophorone diisocyanate 
-- -- 2223 
2223 
urethane 
used for 
Polyol obtained in Synthesis Example 1 
354 -- -- 354 
prepolymers 
reaction 
Polyol obtained in Synthesis Example 2 
-- -- 470 -- 
(g) Polyol obtained in Synthesis Example 3 
-- 232 -- -- 
Polyol obtained in Synthesis Example 4 
-- -- -- -- 
Polyol obtained in Synthesis Example 5 
-- -- -- -- 
Catalyst (dibutyltin dilaurate) 
-- -- 0.6 0.6 
Other Reaction temp. (.degree.C.) 
55 55 70 70 
conditions 
Reaction time (hr) 8 8 5 5 
Temp. of thin-film distillation 
165 165 180 180 
tube (.degree.C.) 
Vacuum degree of thin-film distillation 
1 1 0.5 0.5 
tube (mmHg) 
Characteristics of 
Concentration (wt. % in ethyl acetate) 
70 70 70 70 
urethane prepolymer 
Appearance Light 
Light 
Light 
Light 
solution obtained yellow 
yellow 
yellow 
yellow 
trans- 
trans- 
trans- 
trans- 
parent 
parent 
parent 
parent 
Diisocyanate monomer content (wt. %) 
0.3 
0.3 
0.4 0.3 
NCO content (wt. %) 
10.1 
11.5 
7.6 8.4 
__________________________________________________________________________ 
TABLE 2 
__________________________________________________________________________ 
Examples of Urethane Prepolymers 
5 6 7 8 
__________________________________________________________________________ 
Conditions for 
Amounts for 
80-TDI 1740 
1740 
-- -- 
preparation of 
materials 
Isophorone diisocyanate 
-- -- 2223 
2223 
urethane 
used for 
Polyol obtained in Synthesis Example 1 
-- -- -- -- 
prepolymers 
reaction 
Polyol obtained in Synthesis Example 2 
-- -- -- -- 
(g) Polyol obtained in Synthesis Example 3 
-- -- -- -- 
Polyol obtained in Synthesis Example 4 
408 -- 408 -- 
Polyol obtained in Synthesis Example 5 
-- 807 -- 807 
Catalyst (dibutyltin dilaurate) 
-- -- 0.6 0.6 
Other Reaction temp. (.degree.C.) 
55 55 70 70 
conditions 
Reaction time (hr) 8 8 5 5 
Temp. of thin-film distillation 
165 165 180 180 
tube (.degree.C.) 
Vacuum degree of thin-film distillation 
1 1 0.5 0.5 
tube (mmHg) 
Characteristics of 
Concentration (wt. % in ethyl acetate) 
70 70 70 70 
urethane prepolymer 
Appearance Light 
Light 
Light 
Light 
solution obtained yellow 
yellow 
yellow 
yellow 
trans- 
trans- 
trans- 
trans- 
parent 
parent 
parent 
parent 
Diisocyanate monomer content (wt. %) 
0.3 0.4 0.4 0.4 
NCO content (wt. %) 
9.5 6.8 8.0 6.0 
__________________________________________________________________________ 
Polyurethane Composition Examples 1 to 9 and Comparative Examples 1 to 4 
All of these examples were directed to polyurethane compositions intended 
for use as paints. 
Paint compositions were prepared by mixing the urethane prepolymers which 
had been obtained in Urethane Prepolymer Synthesis Examples 1 to 8, a 
urethane prepolymer commercially available in the name of GP105A (product 
of Mitsubishi Kasel Corporation made as an adduct between tolylene 
diisocyanate and trimethylolpropane and having an NCO content of 13.2% by 
weight and a concentration of 75% by weight) or another urethane 
prepolymer commercially available in the name of NY215A (product of the 
same Japanese company made as an adduct between isophorone diisocyanate 
and trimethylolpropane and having an NCO content of 10.2% by weight and a 
concentration of 75% by weight) with an acrylic polyol commercially 
available in the name of Acrydic A-801 (product of Dainippon Ink & 
Chemicals Inc. having a hydroxyl number of 50 and a concentration of 50% 
by weight), a polyester polyol commercially available in the name of 
Desmophen 1100 (product of Bayer AG having a hydroxyl number of 210) or 
another polyester polyol commercially available in the name of Desmophen 
800 (product of Bayer AG having a hydroxyl number of 290), as shown in 
TABLES 3 to 6 below. 
Each composition was evaluated for the hardening rate of a film thereof and 
for the physical properties of the hardened film. The results are shown in 
TABLES 3 to 6. The evaluation was made in accordance with the methods 
which will hereunder be described. 
(1) Preparation of paint: 
In each example, the urethane prepolymer and the polyol were mixed in 
proportions making a mixture having an NCO/OH value (equivalent ratio) of 
1. 
(2) Dilution: 
The mixed urethane prepolymer and polyol solution was diluted to a 
concentration of about 30% by weight with a mixed solvent prepared by 
mixing xylene, n-butyl acetate, ethyl acetate and Cellosolve acetate in a 
weight ratio of 3:3:3:1. 
(3) Application: 
The diluted solution was applied by air spraying to coat a panel. 
(4) Panel coated: 
The panel was of a bright Bt #144 treated steel sheet and measured 0.6 mm 
by 70 mm by 150 mm. 
(5) Evaluation of a coated film prior to its hardening: 
Hardening and drying time: 
The film was held at 20.degree. C. and the gauze which had been soaked with 
ethyl acetate was rubbed against the film five times to see if the film 
would peel off. It no longer peeled off if it had already hardened and 
dried. 
Tack-free time: 
The film was examined for tackiness by a finger. 
(6) Evaluation of the film as hardened: 
The film was hardened by heating at a temperature of 80.degree. C. for 40 
minutes and was, then, evaluated for its physical properties, as will 
hereinafter be described. 
Pencil hardness: 
This property was examined in accordance with the JIS-5400 method. 
Du Pont impac resistance: 
This property was examined in accordance with the JIS-5400 method using a 
striking die of 0.5 inch diameter and a weight of 500 g. The result is 
shown by the maximum height from which impact could be applied to the film 
without damaging it. 
Adhesiveness: 
This property was examined in accordance with the JIS-5400 method. 
Solvent resistance: 
The gauze which had been soaked with ethyl acetate was rubbed against the 
film 20 times and the film portions which had not been affected were 
compared in area with the original film. The unaffected or remaining film, 
or film portions were also inspected visually. The results are shown by % 
and also by the following symbols: 
.largecircle.--The whole film remained unaffected by the solvent, and 
unchanged in luster; 
.DELTA.--The greater part of the film remained unaffected, but was lower in 
luster; 
x--The greater part of the film was dissolved by the solvent. 
Acid resistance: 
The coated plate was dipped in a 5% aqueous solution of hydrogen chloride 
at 25.degree. C. After 48 hours, the film portions which had not been 
affected were compared in area with the original film. The unaffected or 
remaining film, or film portions were also inspected visually. The results 
are shown by % and also by the following symbols: 
.largecircle.--The whole film remained unaffected by the acid, and 
unchanged in luster; 
.DELTA.--The greater part of the film remained unaffected, but was lower in 
luster; 
x--The greater part of the film was dissolved in the solution. 
Alkali resistance: 
The coated plate was dipped in a 5% aqueous solution of sodium hydroxide at 
25.degree. C. After 48 hours, the film portions which had not been 
affected were compared in area with the original film. The unaffected or 
remaining film, or film portions were also inspected visually. The results 
are shown by % and also by the following symbols: 
.largecircle.--The whole film remained unaffected by the alkali, and 
unchanged in luster; 
.DELTA.--The greater part of the film remained unaffected, but was lower in 
luster; 
x--The greater part of the film was dissolved in the solution. 
TABLE 3 
__________________________________________________________________________ 
Examples of compositions 
1 2 3 4 
__________________________________________________________________________ 
Formulation 
Urethane prepolymer 
Snythesis 
Snythesis 
Snythesis 
Snythesis 
Example 1 
Example 2 
Example 3 
Example 4 
Polyol A-801*.sup.1 
A-801*.sup.1 
A-801*.sup.1 
A-801*.sup.1 
Amount of dibutyltin dilaurate (ppm) 
0 0 500 500 
Hardenability 
Tack-free time (20.degree. C.) 
12 min. 
10 min. 
15 min. 
12 min. 
Hardening and drying time (20.degree.C.) 
3 hours 
3 hours 
4 hours 
3.5 hours 
Physical 
Pencil hardness 4H 5H 3H 4H 
properties of 
Adhesion (crosscut test) 
100/100 
100/100 
100/100 
100/100 
film as 
Du Pont impact resistance test 
50 cm 50 cm 50 cm 50 cm 
hardened 
Solvent resistance*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
(ethyl acetate) 
Alkali resistance (5% NaOH)*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.DELTA. (100) 
.smallcircle. (100) 
Acid resistance (5% HCl)*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
__________________________________________________________________________ 
Notes: 
*.sup.1 Acrylic A801 tradename of Dainippon Ink & Chemicals Inc. 
*.sup.2 Each figure in the parentheses represents % of the area of the 
film found remaining after the test. 
TABLE 4 
__________________________________________________________________________ 
Examples of compositions 
5 6 7 
__________________________________________________________________________ 
Formulation 
Urethane prepolymer 
Synthesis 
Synthesis 
Synthesis 
Example 5 
Example 6 
Example 7 
Polyol A-801*.sup.1 
A-801*.sup.1 
A-801*.sup.1 
Amount of dibutyltin dilaurate (ppm) 
0 0 500 
Hardenability 
Tack-free time (20.degree. C.) 
10 min. 
12 min. 
12 min. 
Hardening and drying time (20.degree.C.) 
3 hours 
3.5 hours 
3 hours 
Physical 
Pencil hardness 4H 4H 5H 
properties of 
Adhesion (crosscut test) 
100/100 
100/100 
100/100 
film as 
Du Pont impact resistance test 
50 cm 50 cm 50 cm 
hardened 
Solvent resistance*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
(ethyl acetate) 
Alkali resistance (5% NaOH)*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
Acid resistance (5% HCl)*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
__________________________________________________________________________ 
Notes: 
*.sup.1 Acrylic A801 tradename of Dainippon Ink & Chemicals Inc. 
*.sup.2 Each figure in the parentheses represents % of the area of the 
film found remaining after the test. 
TABLE 5 
__________________________________________________________________________ 
Examples of compositions 
Comparative 
8 9 Example 1 
__________________________________________________________________________ 
Formulation 
Urethane prepolymer 
Synthesis 
Synthesis 
GP 105A*.sup.3 
Example 8 
Example 1 
Polyol A-801*.sup.1 
D1100*.sup.5 / 
A-801*.sup.1 
D800*.sup.6 = 1/1 
Amount of dibutyltin dilaurate (ppm) 
500 0 0 
Hardenability 
Tack-free time (20.degree. C.) 
15 min. 
12 min. 
20 min. 
Hardening and drying time (20.degree.C.) 
4 hours 
2.5 hours 
5 hours 
Physical 
Pencil hardness 4H 3H 2H 
properties of 
Adhesion (crosscut test) 
100/100 
100/100 
90/100 
film as 
Du Pont impact resistance test 
50 cm 50 cm 40 cm 
hardened 
Solvent resistance*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.smallcircle. (100) 
(ethyl acetate) 
Alkali resistance (5% NaOH)*.sup.2 
.DELTA. (90) 
.smallcircle. (100) 
.DELTA. (90) 
Acid resistance (5% HCl)*.sup.2 
.smallcircle. (100) 
.smallcircle. (100) 
.DELTA. (100) 
__________________________________________________________________________ 
Notes: 
*.sup.1 Acrylic A801 tradename of Dainippon Ink & Chemicals Inc. 
*.sup.2 Each figure in the parentheses represents % of the area of the 
film found remaining after the test. 
*.sup.3 Tradename of Mitsubishi Kasei Corpoation 
*.sup.5 Desmophen 1100 (Tradename of BASF AG) 
*.sup.6 Desmophen 800 (Tradename of BASF AG) 
TABLE 6 
__________________________________________________________________________ 
Examples of compositions 
Comparative 
Comparative 
Comparative 
Example 2 
Example 3 
Example 4 
__________________________________________________________________________ 
Formulation 
Urethane prepolymer 
NY 215A*.sup.4 
Synthesis 
GP 105A*.sup.3 
Example 12 
Polyol A-801*.sup.1 
A-801*.sup.1 
D1100*.sup.5 / 
D800*.sup.6 = 1/1 
Amount of dibutyltin dilaurate (ppm) 
500 0 0 
Hardenability 
Tack-free time (20.degree. C.) 
25 min. 
25 min. 
20 min. 
Hardening and drying time (20.degree.C.) 
7 hours 
6 hours 
4 hours 
Physical 
Pencil hardness 3H 2B H 
properties of 
Adhesion (crosscut test) 
85/100 90/100 95/100 
film as 
Du Pont impact resistance test 
30 cm 40 cm 45 cm 
hardened 
Solvent resistance*.sup.2 
.DELTA. (80) 
.DELTA. (90) 
.smallcircle. (100) 
(ethyl acetate) 
Alkali resistance (5% NaOH)*.sup.2 
X (30) .DELTA. (90) 
.DELTA. (80) 
Acid resistance (5% HCl)*.sup.2 
.DELTA. (90) 
.DELTA. (100) 
.DELTA. (100) 
__________________________________________________________________________ 
Notes: 
*.sup.1 Acrylic A801 tradename of Dainippon Ink & Chemicals Inc. 
*.sup.2 Each figure in the parentheses represents % of the area of the 
film found remaining after the test. 
*.sup.3 Tradename of Mitsubishi Kasei Corporation 
*.sup.4 Tradename of Mitsubishi Kasei Corporation 
*.sup.5 Desmophen 1100 (Tradename of BASF AG) 
*.sup.6 Desmophen 800 (Tradename of BASF AG) 
POLYURETHANE COMPOSITION EXAMPLES 10 AND 11 AND COMATIVE EXAMPLE 5 
All of these examples were directed to compositions intended for use as 
adhesives. 
Urethane adhesive compositions were prepared by mixing the urethane 
prepolymer which had been obtained in Urethane Prepolymer Synthesis 
Example 1 or 5, or the commercially available urethane prepolymer, GP105A 
(product of Mitsubishi Kasei Corporation obtained as an adduct between 
tolylene diisocyanate and trimethylolpropane, and having an NCO content of 
13.2% by weight and a concentration of 75% by weight) with a commercially 
available polyurethane resin containing hydroxyl groups as sold in the 
name of Nippolan 3022 (product of Nippon Polyurethane Industries supplied 
as an ethyl acetate solution having a solid content of 35% by weight), as 
shown in TABLE 7. 
Each adhesive was evaluated for its adhesive strength by the method which 
will hereinafter be described. The results are shown in TABLE 7. 
Method of Evaluation: 
Materials bonded: 
Polyethylene terephthalate films each having a thickness of 125 microns. 
Application: 
An ethyl acetate dilution of the adhesive having a resin content of 20% by 
weight was applied to coat one surface of each of two polyethylene 
terephthalate films. It was applied to give a dry resin coating weight of 
15 g/m.sup.2. 
Pressing: 
The coating was dried at 80.degree. C. for five minutes, whereby the 
solvent was removed. Then, the coated surfaces were placed on each other 
and pressed against each other by application of a pressure of 1 to 3 
kg/cm.sup.2 at room temperature. 
Hardening: 
The coating was hardened by heating at 80.degree. C. for two hours. 
Determination of peel strength: 
A specimen measuring 10 mm by 150 mm was cut from the films which had been 
bonded together and a T-peel test was conducted on it at a pull rate of 
100 mm/min., a temperature of 23.degree. C. and a relative humidity of 
65%. 
TABLE 7 
__________________________________________________________________________ 
Examples of compositions 
Comparative 
10 11 Example 5 
__________________________________________________________________________ 
Formulation 
Urethane prepolymer 
Synthesis 
Synthesis 
GP 105A*.sup.3 
Example 1 
Example 5 
Polyol N 3022*.sup.7 
N 3022*.sup.7 
N 3022*.sup.7 
Urethane prepolymer/polyol 
1/10 1/10 1/10 
(solid weight ratio) 
Adhesive (peel) strength (kg/cm) 
1.8 2.2 0.7 
__________________________________________________________________________ 
Notes: 
*.sup.3 See Note *.sup.3 to Table 5. 
*.sup.7 Tradename of Nippon Polyurethane Industries for polyurethane resi 
containing hydroxyl groups.