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Description  |
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BACKGROUND OF THE INVENTION
Hitherto, flexible polyurethane foams, with large commercial application,
have been based on polyol skeletons such as polyethers and polyesters.
Flexible polyurethanes made from polyethers and polyesters are inherently
subject to hydrolysis because both of the resulting polyurethane foams are
hydrophilic in nature. Although polyether polyurethane foams are more
resistant to hydrolysis than polyester polyurethane foams, both still
suffer from hydrolytic instability, and, therefore, are not usable in
applications which require extended periods in contact with water such as
waterproofing. These two types of flexible polyurethane foams also have
low oxidative resistance and therefore, possess rather poor weathering
properties.
Other flexible polyurethane foams also have been prepared using more
hydrophobic flexible units such as hydroxy terminated polybutadienes and
hydroxy terminated polyethylene-polypropylene copolymers. Although these
flexible polyurethane foams have excellent resistance to hydrolysis, they
both have poor weathering and heat resistance due either to the existence
of double bonds in the case of the polybutadiene polyurethane foams, or
active hydrogens, tertiary hydrogens, in the case of
polyethylene-polypropylene polyurethane foams.
OBJECT OF THE INVENTION
An object of the invention is to solve the above-described shortcomings of
the prior polyurethane foams, and to provide new flexible polyurethane
foams having a host of uniquely superior physical properties such as
waterproofness, low impact resilience, and low transition temperature,
high oxidative resistance, high ozone resistance, low gas permeability,
and other similar properties. The polyurethane foams according to the
present invention will find application in waterproofing, vehicle interior
safety padding in gas retention sealants and other uses require the above
stated properties.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing an infrared spectrum of the polyurethane foam in
Example 1.
FIGS. 2(a) and 2(b) are a front view and a side view showing a waterproof
test method, respectively
1 . . . flat glass, 2 . . . silicone sealant
3 . . . water, 4 . . . foam sample
DETAILED EXPLANATION OF THE INVENTION
As a means for solving the above problems, the invention is a flexible
polyurethane foam having a polyisobutylene skeleton obtained by reacting a
polyol based on polyhydroxy terminated polyisobutylene with a
polyisocyanate in the presence of a blowing agent with two and three
terminal hydroxy groups per polyisobutylene unit preferred.
The hydroxy terminated polyisobutylene skeletons used in the invention are
prepared by means that introduce hydroxy groups into the terminal
positions by dehydrochlorinating, hydroborating and oxidizing
polyfunctional polyisobutylene having terminal chlorine atoms. Said chloro
terminated polyisobutylenes are obtained by cationically polymerizing an
isobutylene monomer
##STR1##
to a molecular weight of 1000-10000. A particularly preferable molecular
weight is 2000-7000.
The polyisocyanate compound used in the invention can be organic
isocyanates having at least two isocyanate groups per 1 molecule, and may
be of low, high or medium molecular weight. As such organic isocyanate,
mention may be made of ethylenediisocyanate, trimethylenediisocyanate,
dodecamethylenediisocyanate, hexamethylenediisocyanate,
tetraethylenediisocyanate, pentamethylenediisocyanate,
propylene-1,2-diisocyanate, 2,3-dimethyltetramethylenediisocyanate,
butylene-1,2-diisocyanate, butylene-1,3-diisocyanate,
1,4-diisocyanate-cyclohexane, cyclopentene-1,3-diisocyanate,
p-phenylene-diisocyanate, 1-methylphenelene-2,4-diisocyanate,
naphthalene-1,4-diisocyanate, toluenediisocyanate,
diphenyl-4,4,-diisocyanate, benzene-1,2,4-triisocyanatae,
xylene-1,4-diisocyanate, xylene-1,3-diisocyanate,
4,4,-diphenylenemethanediisocyanate, 4,4,-diphenylenepropanediisocyanate,
1,2,3,4-tetraisocyanatebutane, butane-1,2,3-triisocyanate,
polymethylenepolyphenyl-isocyanate and the like and in addition to the
above, use may be made of other organic polyisoccyanates having at least
two isocyanate functional groups.
In case of expanding foams by reacting the above materials, water is used
as a blowing agent, but it is possible to add a catalyst, a foam
stabilizer, a viscosity modifier, an organic solvent as a blowing agent,
and each kind of organic or inorganic additives, such as a fire retardant
and the like. As the catalyst, use may be made of amine and tin catalysts
used in case of manufacturing common polyurethane foam, and as the foam
stabilizer, it is possible to use a silicone surfactant hitherto used. As
the organic solvent, mention may be made of low boiling point hydrocarbon
such as pentane, hexane, heptane, pentene, heptene, benzene and the like,
or low boiling point halogenated hydrocarbon such as trichloromonofluoro
methane, dichlorofluoromethane, methylene chloride and the like, and low
boiling point hydrocarbon ether such as tetrahydrofuran, diethylether,
1,4-dioxane and the like, having a role as a blowing agent in addition to
the object of lowering a viscosity.
As a foaming process in the invention, it is possible to use either one of
a prepolymer process or a one-shot process, but the prepolymer process is
preferable in the point of stability at the time of expanding foams.
Since polyisobutylenes having terminal hydroxy groups are hydrophobic and
repell water, such foams show excellent waterproofness. Further, since the
molecular structure does not contain any double bond, ester bond and
methine hydrogen, there is no deterioration caused by hydrolysis,
oxidation and the like, and water resistance is excellent. Moreover, the
polyisobutylene skeleton is a repetition of the following formula.
##STR2##
Foams obtained from the above formula have high hysteresis, that is a
large loss coefficient because the geminal methyl groups that occur on
alternate carbon chain atoms cause the foam to resist externally applied
force by mechanical energy dissipation. Such characteristics give a foam
excellent soundproofing and damping properties. Further, such foams also
exhibit excellent low temperature characteristics because of the low
crystallizability of polyisobutylene and its low glass transition
temperature.
When the molecular weight of polyisobutylene having terminal hydroxy groups
used is less than 1000, the foam becomes hard, and loses its flexibility.
On the other hand, when the molecular weight thereof exceeds 10000, it
becomes difficult to obtain a good foam because the viscosity becomes
extremely high and blowing becomes difficult. Therefore, the molecular
weight of polyisobutylene having terminal hydroxy groups is limited to
within the range of 1000-10000, preferably within the range of 1500-7000.
The foam density can be regulated by the amount of water to be added. In
the prepolymer process for example, the amount of water added to 100 parts
by weight of a prepolymer is preferably 0.5-3.0 part by weight. The reason
therefore is because when the amount is less than 0.5 part by weight, the
foam density becomes too high, while when the amount exceeds 3 parts by
weight, compatibility with water is worse and the cells become too coarse
for a good foam.
The invention will be explained by referring to examples as follows.
EXAMPLE 1
The raw or starting material was a tri-hydroxy terminated polyisobutylene
having a molecular weight of 7000. The manufacturing method is as follows.
As an initiator, 1,3,5-tris (2-methoxypropane)-benzene (hereinafter
abreviated as "TriCuOMe") and BC1.sub.3 were used. The amounts used were
0.041 moles of TriCuOMe and a fivefold equivalent of BC1.sub.3 per methoxy
group. The initiator was dissolved in the solvent methyl chloride, 345 ml
of isobutylene monomer was added thereto inside a dry box under the inert
gas nitrogen at -60.degree. C., and polymerization was carried out by the
living carbocation polymerization method. The polymerization was
terminated by the addition of methanol to obtain about 190 g of tri-chloro
terminated polyisobutylene. AFter extracting a small quantity of low
molecular components from the obtained polymer, dehydrochlorination was
carried out using potassium t-butoxide (t-BuOK) in tetrahydrofuran (THF)
as a solvent to obtain about 165 g of polyisobutylene having a double bond
at each terminal position. Then, the thus obtained polyisobutylene was
dissolved in THF and hydroborated with BH.sub.3, thereafter potassium
hydroxide and hydrogen peroxide solution were added to obtain about 120 g
of polyisobutylene having terinal hydroxy groups. The thus obtained
polymer had a molecular weight of 7000 (measured by VPO), three (3)
hydroxy group (measured by FTIR), and a molecular weight distribution of
Mw/Mn=2.1 (measured by GPC).
100 parts of the hydroxy terminated polyisobutylene (molecular weight 7000,
three (3) hydroxy groups) obtained as described above was reacted with
18.5 parts of an organic isocyanate (made by Mobay, Tradename: Mondur
TD-80) in the presence of 60-100 parts of methylene chloride as a
viscosity depressant at 45.degree. C. for 19 hours to obtain a prepolymer
having 5.7% of isocyanate group (NCO). After producing this prepolymer,
residual methylene chloride was removed. Then, 100 parts of this
prepolymer were mixed with water as a blowing agent, a catalyst, and other
ingredients at a mixing ratio (weight ratio) described at the upper part
of Table 1, and a polyurethane foam having a polyisobutylene resin
skeleton was formed by foaming.
The infrared spectrum of the resulting polyurethane foam is shown in FIG.
1. In the infrared spectrum shown in FIG. 1, a large peak based on
##STR3##
vibration of isobutylene skeleton
##STR4##
is confirmed at 1220 cm.sup.-1.
EXAMPLE 2
Trifunctional terminal hydroxy group polyisobutylene having molecular
weight of 3650 was synthesized by the same method as in Example 1. In this
case, the amount of TriCuOMe used was 0.054 mole, the amount of
isobutylene monomer was 144 ml; the final polyisobutylene having three (3)
terminal hydroxy groups was about 90 g, the molecular weight was 3650, the
terminal hydroxy group number was 3, and the molecular weight distribution
was Mw/Mn=1.7.
100 parts of polyisobutylene having three (3) terminal hydroxy groups
(molecular weight 3650, terminal hydroxy group number 3) obtained as
described above was reacted with 22.4 parts of organic isocyanate (the
same one as in Example 1) in the presence of 30-50 parts of methylene
chloride as a viscosity depressant at 55.sup.0 C. for 17 hours to obtain a
prepolymer having 0.6% of isocyanate group (NCO). The foaming method was
the same as in Example 1 (the mixing ratio is shown in Table 1), and a
polyurethane foam having a polyisobutylene resin skeleton was formed.
From the infrared spectrum of the resulting polyurethane foam, a large peak
based on vibration of isobutylene skeleton is confirmed as shown in
Example 1.
EXAMPLE 3
The raw or starting material is a di-hydroxy terminated polyisobutylene
having a molecular weight of 7000. The manufacturing method is as follows.
As an initiator, 1,3-bis (2-methoxypropane)-benzene (hereinafter abreviated
as "BiCuOMe") and BC1.sub.3 is used. The amounts used were 0.041 moles of
BiCuOMe and a fivefold equivalent of BC1.sub.3 per methoxy group. The
initator is dissolved in the solvent methyl chloride, 345 ml of
isobutylene monomer is added thereto inside a dry box under the inert gas
nitrogen at -60.sup.0 C., and polymerization is carried out by the living
carbocation polymerization method. The polymerization is terminated by the
addition of methanol to obtain about 190 g of di-chloro terminated
polyisobutylene. After extracting a small quantity of low molecular
components from the obtained polymer, dehydrochlorination is carried out
using potassium t-butoxide (t-BuOK) in tetrahydrofuran (THF) as a solvent
to obtain about 165 g of polyisobutylene haivng a double bond at each
terminal position. Then, the thus obtained polyisobutylene is dissolved in
THF and hydroborated with BH.sub.3, thereafter potassium hydroxide and
hydrogen peroxide solution is added to obtain about 120 g of
polyisobutylene having terinal hydroxy groups.
100 parts of the hydroxy terminated polyisobutylene (molecular weight 7000,
two (2) hydroxy groups) obtained as described above is reacted with 14.0
parts of an organic isocyanate in the presence of 60-100 parts of
methylene chloride as a viscosity depressant at 45.sup.0 C. for 19 hours
to obtain a prepolymer having 5.7% of isocyanate group (NCO). After
producing this prepolymer, residual methylene chloride is removed. Then,
100 parts of this prepolymer is mixed with water as a blowing agent, a
catalyst, and other ingredients at a mixing ratio (weight ratio) described
at the upper part of Table 1, and a polyurethane foam having a
polyisobutylene resin skeleton is formed by foaming.
EXAMPLE 1
100 parts of polybutadienepolyol (made by ARCO, Tradename: R-45HT,
functional group number 2-3) was reacted with 22.3 parts of organic
isocyanate (the same as in Example 1) at 50.sup.0 C. for 2 hours to obtain
a prepolymer of 5.7% of isocyanate group (NCO). With the use of 100 parts
of this prepolymer, polybutadienepolyurethane foam was formed by mixing at
the mixing ratio (weight ratio) described in the part of Table 1.
COMPARATIVE EXAMPLE 2
100 parts of polyetherpolyol (made by Dow, Tradename: Voranol, functional
group number 3) was reacted with 24.1 parts of organic isocyanate (the
same as in Example 1) at 55.sup.0 C. for 18 hours to obtain a prepolymer
having 5.6% of isocyanate group (NCO). With the use of 100 parts of this
prepolymer, a polyetherpolyurethane foam was formed by mixing at the
mixing ratio (weight ratio) described in the upper part of Table 1.
In the lower part of Table 1 are shown physical properties measured values
of polyurethane foam samples manufactured in the above examples and
comparative examples. In Table 1, thermal resistance and moist heat
resistance tests shows values obtained by ASTM D357. Further, as to the
impact resilience test, a steel ball of 8 mm in diameter was dropped from
a height of 500 mm on a 5 mm thick rebound sample through a glass tube,
and a value was obtained from the height of the bounce. As to the
waterproof test, as shown in FIGS. 2(a) and 2(b), a foam sample of 4-5 mm
in thickness, 1 cm in length and 2 cm in breadth was sandwiched between
two flat glass plates 1 and compressed 60%, thereafter the flat glass
plates were fixed together by a silicone sealant 2, water 3 was placed at
a height of 5 cm from the upper surface of the foam (hydraulic pressure 5
g/cm.sup.2), and the time measured was that elapsed between placing water
on the foam and the first appearance of water passing through the foam. To
facilitate the observation of the first drop of water leaving the bottom
surface of the colorless foam the water was dyed by a drop or two of blue
ink.
TABLE 1
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Example Comparative
1 2 1 2
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Compo- Prepolymer 100 100 100 100
sition Water 1.2 1.1 1.2 1.2
Catalyst 3.0 3.0 2.0 2.5
DABCO-33LV
Air Product Co.
Silicon 5043 0.2 1.5 1.0 1.8
Dow Corning
Methylene chloride
5.0 4.6 5.0 3.0
Tetrahydrofuran
5.6 3.5 -- --
Physical
Density (g/cm.sup.3)
0.092 0.098
0.119
0.124
Proper-
Tensile strength
1.19 2.48 2.27 0.86
ties (kg/cm.sup.2)
Extensibility (%)
124 106 124 130
Impact resilience
3.9 8.3 34.7 12.5
test (%)
Waterproof text
13,300 57,900
170 55
(sec)
Thermal resistance
test*.sup.1
Tensile strength
-3.4 -2.4 -64.9 -2.4
loss (%)
Extensibility -5.6 -5.6 -79.2 -4.8
loss (%)
Wet heat resistance
test*.sup.2
Tensile strength
-1.7 -5.4 -15.3 -9.5
loss (%)
Extensibility -0.8 -3.3 -13.8 -8.1
loss (%)
______________________________________
.sup.*1 Thermal resistance test condition: 140.degree. C., 22 hours
.sup.*2 Wet heat resistance test condition: 100.degree. C., 100% humidity
3 hours
As indicated by the data in Table 1the polyurethane foam having the
polyisobutylene skeleton according to the invention exhibits excellent
tensile strength and wet heat resistance as compared with a widely used
polyesther polyurethane foam, and also shows excellent water repellency
and waterproofness. Further, as compared with the
polybutadiene-polyurethane foam having a double bond in the molecule
(Comparative Example 1), the polyurethane foam according to the invention
has far superior thermal resistance, wet heat resistance and
waterproofness.
EFFECT OF THE INVENTION
As explained above, the polyurethane foam made with the polyisobutylene
skeleton according to the invention has an outstanding combination of
physical properties, such as excellent tensile strength, wet heat
resistance, thermal resistance, oxidation resistance, low gas permeation
properties, and low temperatures characteristics together with excellent
waterproofness and impact resilience.
While the preferred embodiment of the invention has been described above,
it is to be understood that the invention is not limited thereto or
thereby but that the scope of the invention is defined by the appended
claims.
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